AMERICAN MOBILE SATELLITE CORP
10-K, 1998-03-31
COMMUNICATIONS SERVICES, NEC
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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-K
              ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                   For the fiscal year ended December 31, 1997
                         Commission file number 0-23044

                      AMERICAN MOBILE SATELLITE CORPORATION
             (Exact name of registrant as specified in its charter)

                        DELAWARE           93-0976127
                   (State or other     (I.R.S.  Employer 
                   jurisdiction of    Identification No.)
                   incorporation or
                    organization) 

           10802 Parkridge Boulevard
                  Reston, VA                          20191-5416
    (Address of principal executive offices)          (Zip Code)

       Registrant's telephone number, including area code: (703) 758-6000
        Securities registered pursuant to Section 12(b) of the Act: None
           Securities registered pursuant to Section 12(g) of the Act:
                     Common Stock, $0.01 per value per share
                                (Title of class)

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  registrant  was
required  to file  such  report(s),  and (2) has  been  subject  to such  filing
requirements for the past 90 days. Yes X No

Indicate by check mark if disclosure of delinquent  filers  pursuant to Item 405
of Regulation  S-K is not contained  herein,  and will not be contained,  to the
best of registrant's  knowledge,  in definitive proxy or information  statements
incorporated  by  reference in Part III of this Form 10-K or any  amendments  to
this Form 10-K. X

The aggregate market value of shares of Common Stock held by  non-affiliates  at
March 27, 1998 was approximately $142,757,227.

Number of shares of Common Stock outstanding at March 27, 1998:  25,176,726.

This Annual Report on Form 10-K omits certain supplemental financial information
required by Rule 3-09 of Regulation S-X.

                       DOCUMENTS INCORPORATED BY REFERENCE

Certain  information in the Company's  definitive  Proxy  Statement for its 1998
Annual Meeting of  Stockholders is incorporated by reference in Part III of this
Form 10-K.










<PAGE>



                      AMERICAN MOBILE SATELLITE CORPORATION


                         1997 Annual Report on Form 10-K


                                     PART I

This Annual Report on Form 10-K includes "forward-looking statements" within the
meaning of Section  27A of the  Securities  Act of 1933 and  Section  21E of the
Securities  Exchange Act of 1934.  Such  statements are identified by the use of
forward-looking  words or phrases  including,  but not limited  to,  "believes,"
"intended,"   "will  be   positioned,"   "expects,"   "expected,"   "estimates,"
"anticipates" and "anticipated." These  forward-looking  statements are based on
the Company's  current  expectations.  All statements  other than  statements of
historical  facts included in this Annual Report,  including those regarding the
Company's financial position,  business strategy,  projected costs and financing
needs,  and plans and  objectives  of  management  for  future  operations,  are
forward-looking statements.  Although the Company believes that the expectations
reflected in such  forward-looking  statements are  reasonable,  there can be no
assurance  that  such  expectations  will  prove to have been  correct.  Because
forward-looking statements involve risks and uncertainties, the Company's actual
results  could  differ  materially.  Important  factors  that could cause actual
results  to  differ  materially  from the  Company's  expectations  ("Cautionary
Statements")  are disclosed under  "Business" and  "Management's  Discussion and
Analysis of Financial  Condition  and Results of  Operations,"  and elsewhere in
this Annual Report,  including,  without  limitation,  in  conjunction  with the
forward-looking statements included in this Annual Report. These forward-looking
statements  represent the  Company's  judgment as of the date hereof and readers
are cautioned not to place undue reliance on these  forward-looking  statements.
All subsequent written and oral forward-looking  statements  attributable to the
Company or persons  acting on behalf of the Company are  expressly  qualified in
their entirety by the Cautionary Statements. Readers should carefully review the
risk factors  described in other  documents  the Company files from time to time
with the  Securities  and Exchange  Commission,  including the Current Report on
Form 8-K filed on March 9, 1998, and Form 10-Q Quarterly  Reports to be filed by
the Company  subsequent to this Form 10-K Annual Report and any Current  Reports
on Form 8-K and registration statements filed by the Company.



                                      - 1 -

<PAGE>



Item 1.  Business.

                                    Overview

American  Mobile  Satellite  Corporation  (the "Company" or "American  Mobile"),
through  its  subsidiaries,   is  a  leading  provider  of  nationwide  wireless
communications services, including data, dispatch, and voice services, primarily
to business  customers in the United States. On March 31, 1998,  American Mobile
acquired ARDIS Company ("ARDIS") from Motorola, Inc. ("Motorola"),  and combined
the ARDIS terrestrial-based  business with the satellite-based business operated
through its  subsidiary  AMSC  Subsidiary  Corporation.  The Company's  combined
network  offers a broad  range of  end-to-end  wireless  solutions  utilizing  a
seamless  network  consisting  of  the  nation's  largest,  most  fully-deployed
terrestrial wireless data network and a satellite in geosynchronous orbit.

American Mobile

American Mobile, a leading provider of nationwide mobile data and voice dispatch
service,  operates North America's first high-powered,  satellite-based  digital
mobile  communications  system.  American  Mobile  provides  a  broad  range  of
integrated end-to-end wireless solutions to land, sea and air-based customers in
a service area (the "Service Area") consisting of the continental United States,
Alaska, Hawaii, Puerto Rico, the U.S. Virgin Islands and U.S. coastal waters and
airspace.

American Mobile provides data service through two network configurations, either
a "satellite-only"  service network or a "multi-mode"  terrestrial and satellite
service network.  American Mobile's  satellite-only data  communications  system
provides data services primarily to long-haul trucking customers.  The Company's
multi-mode  communications  system uses the Company's  terrestrial and satellite
networks  to  provide   "least-cost   routing"  for   customers'   two-way  data
communications  by actively  seeking  connections to the lower cost  terrestrial
network before  automatically  using the Company's  satellite  network,  thereby
providing cost-effective nationwide coverage.

In addition to  providing  data  service,  American  Mobile  offers two forms of
mobile voice communications  service:  nationwide dispatch service and satellite
telephone service.  American Mobile is the only company that offers a nationwide
dispatch  service  which  allows  multiple  users  located  anywhere in American
Mobile's   extensive   service   area  to   share  a   single   connection   for
point-to-multipoint  communication using push-to-talk handsets.  American Mobile
markets its nationwide  dispatch service  primarily to field services users with
wide-area fleet  communications  needs.  American Mobile's  satellite  telephone
service  provides  traditional  voice,  fax and data service  through  satellite
terminals  that are  similar to cellular  phones.  American  Mobile  markets its
satellite  telephone  service  primarily  to  maritime  users,   including  both
commercial and  recreational  vessels,  as well as other market segments such as
government and public safety organizations.

As of  December  31,  1997,  American  Mobile  had  approximately  32,400  units
operating on its network.


                                      - 2 -

<PAGE>



ARDIS

ARDIS,  a leading  provider of nationwide  wireless  data  service,  markets its
service  primarily  to  business  customers  with a need for  reliable,  two-way
wireless data  communications in the field services and transportation  markets.
The ARDIS  wireless data network  provides the widest breadth of coverage of any
single  provider  of  terrestrial  wireless  service in the United  States.  The
network  incorporates  approximately  1,700 radio  towers (base  stations)  that
provide  service to 425 of the  largest  cities and towns in the United  States,
including  virtually all metropolitan  areas. The network was designed and built
using Motorola technology to provide reliable two-way data communications,  deep
in-building  penetration and efficient  frequency usage. The extensive  coverage
and deep in-building  penetration provided by the ARDIS network is attractive to
customers who desire a single service  provider whose  nationwide  scope extends
from large  metropolitan  areas to  smaller  cities  and  towns.  Customers  use
applications  such as service call dispatch,  asset tracking,  and  peer-to-peer
communications  to achieve critical business  objectives  resulting in increased
productivity, profitability and customer satisfaction.

As of  December  31,  1997,  ARDIS had  approximately  55,400  units  (including
approximately  6,500 units,  common to both American Mobile and ARDIS) operating
on its network.


AMRC

American Mobile Radio Corporation, a subsidiary of AMRC Holdings, Inc. (together
with American Mobile Radio Corporation,  "AMRC") has been granted a license from
the  Federal  Communications  Commission  (the "FCC") to  construct,  launch and
operate a domestic satellite system for the provision of satellite-based digital
audio radio  service  ("DARS").  AMRC made a payment of $90 million to fully pay
for its DARS  license in October  1997.  The Company  currently  owns 80% of the
capital  stock of AMRC.  The  remainder  of AMRC is  owned by  WorldSpace,  Inc.
("WorldSpace"), a leading international DARS company that is planning to provide
DARS service to Latin America,  Africa and Asia. Through its investment in AMRC,
WorldSpace  has an option to increase its  ownership in AMRC to 72%,  subject to
FCC approval. It is anticipated that the proceeds resulting from the exercise of
the option will not be available  to the Company.  As  previously  reported,  on
March  20,  1998,   AMRC  entered  into  an  agreement  with  Hughes  Space  and
Communications  International,  Inc. to build two new  generation,  high-powered
HS-702  geostationary  orbit  satellites  for its digital  radio  service,  with
service anticipated to begin in the year 2000.


                                     History

The Company,  a Delaware  corporation,  was incorporated in May 1988 by eight of
the  initial  applicants  for  the  first  mobile  satellite  services  license,
following  a  determination  by the FCC that the public  interest  would best be
served by  granting  the  license to a  consortium  composed  of all willing and
qualified

                                      - 3 -

<PAGE>



applicants. In March 1991, the Company transferred the mobile satellite services
license to its wholly owned subsidiary, AMSC Subsidiary Corporation.

In August 1989, the FCC authorized the Company to construct,  launch and operate
a mobile satellite communications system. For the system's mobile links, the FCC
assigned  to the  Company the  exclusive  license to 30 MHz of L-band  spectrum,
subject to international frequency  coordination.  L-band spectrum is considered
advantageous for mobile  communications  services because it is less affected by
radio propagation difficulties than are higher frequencies. The FCC licensed the
Company  to  provide  a  full  range  of  mobile   voice,   data  and   dispatch
communications  services via satellite to land,  air and sea-based  customers in
the Service Area.


                                 The Acquisition

On March 31, 1998, the Company acquired ARDIS (the  "Acquisition") in accordance
with a purchase agreement (the "Purchase  Agreement") entered into with Motorola
on December 31, 1997.  Subject to certain purchase price adjustment  provisions,
the Company  acquired  ARDIS for a purchase price of $100 million (the "Purchase
Price")  paid as follows:  (i) $50  million in cash,  paid at the closing of the
Acquisition;  (ii)  approximately  $38 million in shares of the Company's Common
Stock,  paid at the  closing of the  Acquisition;  and (iii)  approximately  $12
million  in shares of the  Company's  Common  Stock and  warrants  for shares of
Company's Common Stock only if, at the annual meeting of Company's stockholders,
the stockholders  approve the issuance of the additional  shares and warrants to
Motorola. The holders of approximately 76% of Company's Common Stock outstanding
and entitled to vote thereon have agreed with  Motorola  that they will vote for
approval of such issuance.

In connection with the  Acquisition,  the Company and its  subsidiaries  entered
into  agreements  with respect to three  financings and  refinancings:  (1) $335
million of Units  consisting  of 12 1/4% Senior  Notes due 2008 and  Warrants to
purchase  shares of Common  Stock of the Company;  (2) a $100 million  Revolving
Credit  Facility and a $100 million Term Loan Facility  (collectively,  the "New
Bank  Financing");  and (3) a $10 million  commitment  with  respect to Motorola
vendor  financing.  See  "Management's  Discussion  and  Analysis  of  Financial
Condition and Results of Operations - Liquidity and Capital Resources."

Upon completion of the  Acquisition,  ARDIS became a wholly-owned  subsidiary of
AMSC Acquisition Company, Inc. ("Acquisition  Company").  In connection with the
Acquisition,  the Company also transferred all of its rights, title and interest
in three additional subsidiaries -- American Mobile Satellite Sales Corporation,
AMSC Subsidiary  Corporation and AMSC Sales Corporation,  Ltd. -- to Acquisition
Company.  As a result,  each of these entities is a  wholly-owned  subsidiary of
Acquisition Company that, in turn, operates as a wholly-owned  subsidiary of the
Company. The Company continues to retain its direct ownership interest in AMRC.

The full benefits of a combination  of American  Mobile and ARDIS as a result of
the Acquisition  will require the integration of each company's  administrative,
finance, sales and marketing  organizations,  the coordination of each company's
sales efforts and the implementation of appropriate  operational,  financial and

                                      - 4 -

<PAGE>

management systems and controls. There can be no assurance that the Company will
be able to integrate  the  operations  of American  Mobile and the ARDIS network
successfully  or, if successful,  that such  integration will yield the expected
benefits to the Company.


                                   The Network

Following the Acquisition,  the Company's  integrated  network consists of (i) a
satellite in geosychronous orbit with coverage of the continental United States,
Alaska, Hawaii, Puerto Rico, the U.S. Virgin Islands and U.S. coastal waters and
airspace,  and (ii) the largest two-way  terrestrial  data network in the United
States with  coverage of over 425 of the largest  cities and towns in the United
States,  including virtually all metropolitan areas. The network provides a wide
range  of  mobile  data  and  voice  services  in  multi-mode  and   single-mode
configurations.

Users of the Company's terrestrial and satellite  communications  network access
the network through subscriber units that may be portable,  mobile or stationary
devices. Generally,  subscriber units enable either data or voice communications
and are designed to operate over either the terrestrial data-only network or the
satellite  network,  which  provide  both  voice  and  data  communications.  In
addition,  the Company's multi-mode  subscriber equipment is designed to provide
least-cost  routing of data  messages  over both the  terrestrial  and satellite
networks.

Subscriber  units  receive and transmit  wireless  data or voice  messages  from
either terrestrial base stations or the Company's satellite, MSAT-2. Terrestrial
messages are routed to their destination via Company-owned data switches,  which
connect to the  public  data  network.  Satellite  messages  are routed to their
destination  via  satellite  data and voice  switches,  located at the Company's
headquarters,  which connect to the public data and switched voice  networks.  A
data switch located in Cedar Rapids links the terrestrial and satellite networks
for the delivery of the Company's multi-mode data service.

The Company's  terrestrial  network delivers superior  in-building  penetration,
completion  rates and response  times  compared to other  wireless data networks
through  the  use  of a  patented  single  frequency  reuse  ("SFR")  technology
developed by Motorola.  SFR technology enables multiple base stations in a given
area to use the same frequency.  As a result, a message sent by a subscriber can
be received by a number of base stations.  This  technology  contrasts with more
commonly used multiple  frequency  reuse ("MFR")  systems which provide for only
one  transmission  path  for a  given  message  at a  particular  frequency.  In
comparison  with  MFR  systems,   the  Company's  technology  provides  superior
in-building   penetration   and  response  times  and  enables  the  Company  to
incrementally  deploy  additional  capacity  as  required,  instead of in larger
increments as required by most wireless networks.




                                      - 5 -

<PAGE>



                                Business Strategy

The Company's  objective is to maximize its revenues by  delivering  value-added
services to end users in specific market segments. To meet this objective and to
capitalize  upon the  competitive  advantages  resulting from the combination of
American Mobile and ARDIS, the Company intends to: (i) offer business  customers
a broad range of nationwide wireless service and end-to-end data solutions; (ii)
integrate  and  leverage  the  advantages  of  its  nationwide  terrestrial  and
satellite data networks; (iii) enhance market penetration by lowering customers'
"total cost of  ownership;"  and (iv) expand the use of  alternate  distribution
channels to accelerate network loading.

Offer Business  Customers a Broad Range of Nationwide  Wireless  Solutions.  The
Company believes its corporate customers prefer a single-source service provider
capable of delivering a broad range of efficient and cost effective solutions to
meet their need for mobile wireless communications. The Company believes that it
has and will  continue  to have a unique  strategic  advantage  in being able to
provide one-stop  shopping across a broad range of products,  including  two-way
paging and advanced  messaging,  packaged e-mail and LAN solutions,  custom data
applications,  dual mode  terrestrial/satellite  data,  and satellite  voice and
dispatch functions.

Integrate and Leverage Network  Advantages.  The Company has spent over a decade
developing and deploying its nationwide  terrestrial and satellite  networks and
now seeks to accelerate growth by leveraging its integrated network. Unlike many
competitors  with plans to build out limited  city-wide or regional  terrestrial
networks or to launch satellites,  the Company's technology infrastructure is in
place and operational today, with future network expansion  requirements arising
primarily  from  increased  customer  demand.  The  Company  believes  that this
integrated  terrestrial/satellite  network  provides key competitive  advantages
currently  unmatched by any  competitor:  virtually 100%  nationwide  geographic
coverage,  guaranteed  message delivery,  and, in the areas covered by the ARDIS
network,  deep  in-building  penetration.  By integrating  the operations of its
terrestrial and satellite  networks,  the Company  expects to achieve  operating
efficiencies  and  economies  of scale that it  believes  will lead to  improved
operating margins.

Enhance  Market  Penetration By Reducing  Customers'  "Total Cost of Ownership."
Historically,   the  most  significant   obstacle  to  the   implementation   of
enterprise-wide  wireless data  applications  has been the relatively high total
cost of  ownership.  The total cost of ownership  is comprised of three  primary
elements:  the cost of the subscriber unit, the required  investment in software
development,  and the monthly cost of network  access and usage.  In most of the
Company's  applications,  the monthly cost of network  access and usage has been
the least prohibitive of these elements.  Until recently,  subscriber unit costs
in excess of $3,000 and custom  software  investments  of up to several  million
dollars were common. By working with business  partners and vendors,  and making
strategic  software  investments,  the Company has  succeeded  in  significantly
lowering  customers' total cost of ownership.  New subscriber  units,  including
low-cost  two-way  messaging units and laptop modem cards, are now available for
$500 or less and  substantial  development  work is underway with several of the
Company's  vendors to accelerate  reductions of equipment  cost, unit weight and
size.  In the future,  the Company  expects that the increased  subscriber  unit

                                      - 6 -

<PAGE>


volumes  associated  with recent large  contract  awards will lead to additional
unit price reductions. In addition, customers can now use off-the-shelf software
applications  that are relatively  inexpensive,  or in the case of the Company's
two-way  messaging  service,  free. The Company  believes that these lower price
points will accelerate the adoption of the Company's  services in its historical
markets,  and will enable the Company to develop new  markets,  such as wireless
point-of-sale and telemetry.


Expand Alternate  Distribution  Channels. The Company sells it service primarily
through a direct  sales  force and  resellers.  In order to  accelerate  network
loading,  the  Company  expects  to  expand  its  use of  indirect  distribution
channels.  To date,  the Company has entered into  agreements  with resellers to
penetrate  markets where such resellers have a market presence and significantly
greater  resources than the Company,  including  dedicated sales  personnel.  In
addition,  the  Company is in the  process of  establishing  relationships  with
existing paging  companies,  paging resellers,  and other targeted  distribution
partners to market two-way guaranteed  messaging services.  The Company believes
that the resale of its  network is an  alternative  that paging  companies  will
consider when assessing a move from one-way to two-way  messaging because it may
reduce  or   eliminate   the  need  for   additional   investment   in   network
infrastructure.  The  Company  intends to  utilize  paging  companies  and other
similar  partners with well  established  distribution  capabilities  to develop
markets outside of the Company's historical market segments.


                           Marketing and Distribution

The Company  markets its services  through four primary  distribution  channels:
direct sales, vertical resellers, horizontal resellers and dealers.


Direct Sales

The Company has a direct sales force who focus on the  requirements  of business
customers.  This sales  organization  is comprised of a national  accounts group
that  profiles  and  targets  specific  Fortune 500  accounts,  and a network of
regionally based  representatives  who specialize in specific industry segments.
Sales to national account targets generally require a sustained marketing effort
lasting several  months.  Prior to making a buying  decision,  a majority of the
accounts  exercise a due diligence  process where  competitive  alternatives are
evaluated.  The Company's  employees  often assist in  developing  justification
studies, application design support, hardware testing, planning and training.


Vertical Resellers

In  order  to  penetrate  quickly  certain  market  segments   characterized  by
specialized  technical  requirements  and/or unique business  applications,  the
Company leverages the capabilities of specialized  distribution partners.  These
relationships  enable the  Company to  penetrate  new  market  segments  without

                                      - 7 -

<PAGE>


investing  in the  product,  training  and  development  requirements  typically
associated with entry into a new market segment.

The Company's resale arrangements are specifically  designed to accelerate entry
into the  wireless  telemetry  (utility  and alarm  monitoring),  point-of-sale,
maritime and government market segments. These business partners are responsible
for  development  of  the  end-user  solutions,  and  purchase  capacity  on the
Company's data network.

Value added service providers  ("VASPs")  represent one of the Company's primary
distribution  channels for maritime  satellite  telephony.  VASPs  purchase bulk
minutes,  resell at a margin, set the price, take risk of collection and perform
all service and billing functions.

The Company currently utilizes three specialized  government  resellers,  one of
which has included the Company's products on the general services administration
schedule.  The Company intends to expand the distribution  opportunities for its
terrestrial data products by also including them in these programs.

The Company also has various  private network  customers  ("PNCs") that purchase
bulk  satellite  capacity  from the  Company in the form of  dedicated  capacity
increments or channels.  PNCs use this capacity to support their own proprietary
networks  and  products,   and  maintain  all  associated   business  risks  and
responsibilities.


Horizontal Resellers

The Company utilizes a series of resale relationships  designed to reach a large
segment  of  the  mobile  workforce  that  does  not  require  integration  with
centralized  systems,  but  still has a broad  need for  two-way  messaging  and
wireless e-mail access.  Because these  applications are generic across numerous
industries, the segment is horizontally addressable,  and requires some level of
retail  presence.  To achieve  this  presence,  the Company is in the process of
establishing relationships with existing paging companies,  paging resellers and
other  targeted  distribution  partners to market two-way  guaranteed  messaging
services.  The  Company  also  maintains  relationships  with  manufacturers  of
personal  handheld  computing  devices,  who  include  the  Company's  marketing
material  with the device  packaging  to  provide  the  purchaser  the option of
wirelessly enabling a handheld computing device.


Dealer Channels

The  Company  also uses land mobile and  maritime  dealers  who  distribute  the
Company's  nationwide dispatch and satellite  telephony products.  These dealers
typically  have  strong  business  relationships  with  regional  public  safety
entities,  as well as with smaller field service fleets and maritime users.  The
Company believes that opportunities exist to capitalize on the strengths of this
channel  by  introducing  a  low  cost  terrestrial  data  device  with  minimum
integration requirements.  Typically these dealers serve as agents for sales and

                                      - 8 -

<PAGE>


service and do not set pricing or provide billing and collection services. These
dealers  are  generally  compensated  with a modest  percentage  of the  service
revenue for which they are responsible.


Customer Concentration

After giving pro forma effect to the Acquisition, three existing customers, IBM,
NCR and  Pitney  Bowes,  accounted  for  26%,  7% and 5%,  respectively,  of the
Company's  recurring  service  revenue for the twelve months ended  December 31,
1997.  The loss of one or more of such  customers,  or any event,  occurrence or
development  which adversely  affects the  relationship  between the Company and
such customer could have a material adverse effect upon the Company.


                        Equipment; Supplier Relationships

The  Company  has   contracts   with  multiple   vendors  to  supply   equipment
configurations  designed to operate on each of its  operating  platforms.  These
devices are designed to meet the requirements of specific end-user applications.
The Company  continues to pursue  enhancements to these devices that will result
in additional desirable features and reduced cost of ownership. Although many of
the  components  of the  Company's  products  are  available  from a  number  of
different suppliers, the Company does rely upon a few key suppliers.

In connection with its mobile data communications service, the Company presently
has an agreement with Trimble  Navigation,  Limited to supply its satellite data
unit. In addition,  multi-mode data terminals are sourced from Rockwell Collins,
Inc. The Company also has contracted with Vistar,  Inc., a Canadian company, for
the development of a new multi-mode terminal.  The new terminal will incorporate
design  changes that will  simplify the  installation  process and allow for the
addition of enhancements  in a modular  fashion.  The Company  believes that the
price of multi-mode terminals will continue to decline in the coming years.

There are currently over 30 different  types of subscriber  units available from
15  manufacturers  that can  operate on the  terrestrial  network.  Examples  of
portable  subscriber units include  ruggedized laptop computers,  small external
modems,  handheld  or palmtop  "assistants,"  pen based  "tablets,"  and two-way
messaging devices, such as the RIM Interactive PagerTM.  Significant  developers
of devices  that are  compatible  with the  network  include  Motorola,  RIM and
Itronix.  Motorola and RIM  manufacture  modems  designed to be integrated  into
handheld field service  terminals,  telemetry  devices,  utility  monitoring and
security systems as well as other computing systems.  RIM recently has developed
the Interactive  PagerTM that supports the Company's two-way messaging  service.
Itronix  manufactures  the XC-6000,  a fully  ruggedized  laptop computer with a
standard keyboard and an integrated wireless modem.

Mobile  satellite  voice  telephones  are  offered  in  a  number  of  different
configurations  that deliver a variety of features and options to meet  specific
market needs. Mobile satellite telephones are currently available in land mobile
vehicle installed, fixed site, maritime, aeronautical, dual mode voice/direct to
home satellite  television and fully  transportable  (i.e.,  battery powered and
packaged in a briefcase)  configurations.  Subscriber  equipment  for  satellite
telephone service and nationwide  dispatch service includes data interface ports

                                      - 9 -

<PAGE>



to allow connection to  communications  accessories such as personal  computers,
and global positioning  satellite ("GPS") tracking devices.  Recent enhancements
allow users to utilize the dispatch  product  remotely  from the vehicle,  via a
wireless  tether.  American  Mobile  continues  to add  enhancements  based upon
customer  requirements,  and has several  initiatives  that could  result in the
reduced cost of end-user devices.  The primary suppliers for the voice equipment
are  Westinghouse  Electric,  Inc.   ("Westinghouse")  and  Mitsubishi  Electric
Corporation.

Tandem  computer  provides  the  ARDIS  network  switching   computers  under  a
multi-year lease that extends through the year 2000, while AT&T provides network
services  including a nationwide  wireline data network,  and leased sites which
house regional ARDIS  switching  equipment.  The Company also has a relationship
with AT&T as its  vendor for  switched  inbound  and  outbound  public  switched
telephone  network  services.  The satellite  system  terminates  calls from its
telephone product via both the AT&T and Sprint networks.

ARDIS has executed  multiple  agreements  with Motorola that provide for certain
continued  support from  Motorola  with  respect to:  supply and support for the
ARDIS DataTAC  network  infrastructure;  ongoing  maintenance and service of the
ARDIS base stations; and lease administration  services for approximately 37% of
ARDIS' base station site leases. Additionally,  Motorola is expected to continue
to manufacture  modems compatible with the ARDIS network  infrastructure for use
in end-user devices.

Hughes Network Systems Ltd, of the United Kingdom, manufactures and supports the
key component to the Company's  multi-mode  and  satellite  messaging  products,
which  is the Land  Earth  Station  ("LES").  There  are  currently  four  LES's
operational.  The platform for the Company's voice products,  the communications
ground segment  ("CGS"),  depends upon products from multiple  vendors,  most of
which are generally  commercially  available.  Northern Telecom manufactures and
supports  the core voice  switch.  Digital  Equipment  Corporation  supplies the
computing platform that runs the CGS.

American  Mobile  jointly  owns  certain  patents,   technical  data  and  other
intellectual   property,   including  the  final  mobile  terminal   performance
specification  ("FMPS"),  developed by  Westinghouse,  with the Canadian  mobile
satellite service provider, TMI Communications and Company,  Limited Partnership
("TMI").  The Company  separately  owns other patents,  technical data and other
intellectual  property  developed by Westinghouse at the Company's sole expense.
Certain of the intellectual property used in the development of the CGS is owned
by Westinghouse or licensed from others.  The Company  believes its ownership of
and rights to  intellectual  property  relating to the CGS is sufficient for its
business purposes.

The  ARDIS  network,  and  certain  of its  competitive  strengths  such as deep
in-building penetration, is based upon SFR technology. Motorola holds the patent
for SFR technology.  ARDIS has entered into support  agreements with Motorola to
provide for certain support of the operations of the ARDIS network.

                                     - 10 -

<PAGE>



However,   there  can  be  no  assurance  that  Motorola  will  not  enter  into
arrangements  with  the  Company's  competitors,   or  that  if  it  does,  such
arrangements would not have a material adverse effect on the Company.


                     Satellite Lease and Purchase Agreement

As  previously  reported,  on December  4, 1997,  the  Company  entered  into an
agreement with African  Continental  Telecommunications  Ltd. ("ACTEL") to lease
the  Company's  satellite,  "MSAT-2,"  (the  "Satellite  Lease  agreement")  for
deployment over sub-Saharan  Africa.  The five-year lease provides for aggregate
payments to the Company of $182.5  million.  Simultaneously,  the Company agreed
with TMI to acquire a one-half ownership interest in TMI's satellite,  "MSAT-1,"
(the "Satellite Purchase  Agreement") at an aggregate cost to the Company of $60
million,  payable  in  equal  installments  over  a  five-year  period;  certain
additional payments to TMI of up to one-half of additional net payments received
are  contemplated  in the event that  additional  benefits  are  realized by the
Company with respect to MSAT-2 after the initial five-year lease term. Under the
Satellite Purchase Agreement,  TMI and the Company will each own a 50% undivided
ownership interest in MSAT-1,  will be jointly  responsible for the operation of
MSAT-1, and will share certain satellite operating expenses,  but will otherwise
maintain their separate business operations.

The Satellite  Purchase  Agreement and  Satellite  Lease  Agreement are separate
transactions and reflect separate sets of obligations for the Company. While the
Company believes that if ACTEL defaults under the Satellite Lease Agreement, the
Company  would  be able to  achieve  the  return  of  MSAT-2  from  ACTEL to its
operation in the United  States and  terminate  its payment  obligations  to TMI
under the Satellite  Purchase  Agreement,  there can be no assurances  that such
actions  can be  achieved.  In  addition,  there can be no  assurances  that the
agreements  will operate in  parallel,  or that the Company will not be met with
certain  completion or transactional  risks under the Satellite Lease Agreement.
If it is necessary for the Company to make payments under the Satellite Purchase
Agreement at a time when it is not receiving  payments under the Satellite Lease
Agreement, the Company could be materially and adversely affected.

Closing under the Satellite  Purchase Agreement and Satellite Lease Agreement is
subject  to a number  of  conditions,  including:  United  States  and  Canadian
regulatory approvals;  a successful financing by ACTEL of at least $120 million;
completion of certain  satellite  testing,  inversion and relocation  activities
with  respect  to  American  Mobile's  satellite,  to support  the  contemplated
services  over  Africa;  receipt  of  various  government   authorizations  from
Gibraltar, South Africa and other jurisdictions to support satellite relocation,
including authorizations with respect to orbital slot and spectrum coordination;
and completion of certain system  development  activities  sufficient to support
satellite  redeployment.  On March 13, 1998,  the FCC  provided  approval of the
transactions; Canadian government coordination and approvals remain outstanding.
It  is  anticipated   that  the  closing  under  both   agreements   will  occur
simultaneously in the spring of 1998. It is anticipated that the net proceeds of
the Satellite  Lease  Agreement and Satellite  Purchase  Agreement  will be used
primarily  to repay  the  Company's  Revolving  Credit  Facility,  as well as to
provide the Company with additional liquidity.  In addition,  any amounts repaid

                                     - 11 -

<PAGE>

from the net proceeds of the Satellite  Lease  Agreement and Satellite  Purchase
Agreement  would  reduce  the  commitment  available  to the  Company  under the
Revolving  Credit  Facility.  See  "Management's   Discussion  and  Analysis  of
Financial   Condition  and  Results  of  Operations  --  Liquidity  and  Capital
Resources."  While it is anticipated that these  transactions  would improve the
leverage of and provide  additional  liquidity to the  Company,  there can be no
assurance that such transactions will be consummated simultaneously, or at all.


                        Satellite Back-up and Technology

The Company  presently has an agreement with TMI, the Canadian mobile  satellite
licensee,  for reciprocal  backup,  restoral and excess  capacity usage ("Backup
Capacity") on the other party's satellite in the event of a satellite failure or
a need for  excess  capacity.  In the event that the lease and  redeployment  of
MSAT-2 is consummated, the Company will no longer have available Backup Capacity
from  MSAT-1.  Each of MSAT-2  and MSAT-1  has in the past  experienced  certain
technological  anomalies,  most  recently with respect to MSAT-2 in January 1998
and MSAT-1 in February 1998.  While recent  anomalies have involved either spare
components  or ones which have not had a material  impact on the Company,  there
can be no assurance that either of the satellites will not experience subsequent
anomalies that could adversely affect the Company's financial condition, results
of operations and cash flows. In the event that MSAT-1 experiences  anomalies of
this type or other  types at a time when the  Company  has no back-up  capacity,
there  would be a material  adverse  effect on the  Company.  See  "Management's
Discussion  and  Analysis of  Financial  Condition  and Results of  Operations -
Liquidity and Capital Resources."

The  Company,  as well as TMI,  has  received  a current  recommendation  from a
subcontractor to its satellite  manufacturer  that, pending further results from
an ongoing  investigation,  the satellite  should be operated at modified  power
management levels. The Company and its satellite  manufacturer are investigating
the basis, if any, for this recommendation.  Based on the information  available
to date,  management  believes  that,  even if  maintained,  the  current  power
management  recommendation  would  not have a  material  negative  effect on the
Company's  business  plan  within  the  next  three  to  five  years,  based  on
anticipated  traffic patterns and anticipated  subscriber  levels.  In the event
that traffic patterns or subscriber levels materially exceed those  anticipated,
the power management recommendation, if maintained, could have a material impact
on the Company's long-term business plan.

MSAT-2 has an expected  remaining service life of approximately  eight years and
the expected  remaining life of MSAT-1 is approximately ten years. This expected
remaining service life of each satellite may be affected by a number of factors.
For example, random failure of satellite components could result in damage to or
loss of MSAT-2 or MSAT-1.  It is also  possible that either  satellite  could be
damaged by  electromagnetic  storms or collisions  with other objects,  although
such occurrences are rare. Although the Company believes that the actual service
lives of both satellites may exceed their expected  service lives,  there can be
no assurance that MSAT-2's or MSAT-1's expected service life will be exceeded or
achieved. Although the Company has obtained in-orbit insurance against a failure
of MSAT-2 in the amount of $184 million,  such  insurance  includes a variety of
deductibles,  performance  margins and  exclusions  and it is unlikely  that any
recovery under such insurance  would fully  compensate the Company for losses it
would sustain in such event.  Further,  the proceeds from the in-orbit insurance


                                     - 12 -

<PAGE>


must be used to repay the outstanding  balance of the New Bank Financing and the
remaining  proceeds,  if any,  would be  insufficient  to construct,  launch and
insure the launch of a  replacement  satellite.  There can be no assurance  that
additional  financing  will be  available  to  construct,  launch  and  insure a
replacement satellite or, if available,  will be available on terms favorable to
the  Company.  At present,  there is no  insurance  policy in effect for MSAT-1.
Although there can be no assurance, the Company believes that it will be able to
obtain  insurance with respect to its interest in MSAT-1 in connection  with the
Satellite Purchase Agreement on terms  substantially  similar to those presently
in effect for MSAT-2. In addition,  the in-orbit  insurance policy is subject to
annual renewal,  and there is no assurance that insurance on favorable terms and
at commercially  reasonable  rates will remain available for coverage of MSAT-2,
or be available for coverage of MSAT-1.

In the event that,  following the satellite lease, MSAT-1 ceases to operate, the
Company  would have several  options to replace the lost  capacity,  through the
lease or purchase of capacity on certain Inmarsat satellites, or the launch of a
new  satellite.  However,  each  of  these  options  would  require  substantial
lead-time and  significant  financing.  As a result,  any such delay or need for
significant funds would result in a material adverse effect on the Company.


                                   Competition

The wireless  communications industry is highly competitive and is characterized
by  frequent  technological  innovation.  The  Company  competes on the basis of
providing comprehensive,  end-to-end solutions and a premium level of service in
the markets it serves.  End-to-end  solutions have been assembled working with a
select  group  of  business  partners  who  develop  and  manufacture  software,
middleware  and  hardware  components.  The  Company  differentiates  itself and
provides a premium  level of service due to its unmatched  geographic  coverage,
in-building   penetration,   guaranteed   message   delivery,   and   guaranteed
reliability.

The Company  competes  with a full array of  companies,  from small  startups to
Fortune 500 companies.  Many of these competitors have financial,  technical and
marketing resources in excess of the Company's.  Because the Company competes in
several market segments with a broad range of services,  competing  technologies
may address one or more of the market  segments.  The Company has identified six
major classes of  technologies or services that offer  capabilities  competitive
with  the  Company's  services:   Terrestrial  Packetized  Data;   Cellular/PCS;
Specialized  Mobile Radio  ("SMR")/Enhanced  Specialized  Mobile Radio ("ESMR");
Private Systems; Paging/Narrowband PCS; and Mobile Satellite Services.


                                     - 13 -

<PAGE>



Terrestrial  Packetized  Data.  Companies  using  packetized  data  technologies
provide  wireless  data  services  that  compete  directly  with a number of the
Company's data products.  Packetized data technology relies on radio frequencies
to transmit short-burst data messages. Primary competitors using this technology
include  RAM  Mobile  Data  ("RAM"),  Metricom,  Teletrac  and  Cellnet.  RAM, a
wholly-owned  subsidiary of BellSouth  enterprises,  operates a terrestrial-only
network that provides data services to customers primarily in the field service,
transportation  and utility  industries.  The Company  believes that its network
provides broader  coverage,  and superior  in-building  penetration  compared to
RAM's network. In addition, the Company is upgrading its network in major cities
so that it will  operate  at  faster  speeds  than the RAM  network.  Metricom's
Ricochet  service  provides  wireless,  mobile access to the  Internet,  private
intranets, local area networks and e-mail. Metricom currently offers its service
in limited regions comprised of San Francisco,  Seattle, Houston and Washington,
D.C. Teletrac  provides  primarily  location and vehicle  monitoring and two-way
data transfer services in major metropolitan areas and Cellnet provides wireless
meter reading services.

Cellular and PCS. Cellular and PCS services compete with the Company's satellite
and  terrestrial  voice and data services,  and presently  serve the majority of
mobile communications users in the United States, with approximately  55,000,000
units.  Cellular  and PCS systems  operated  by  approximately  1,500  companies
collectively  provide  service  throughout  most of the United  States,  with no
single  competitor  providing the breadth of coverage that is available  through
the Company's  network.  Cellular  Digital  Packet Data  ("CDPD"),  the cellular
industry's   standard   packet  data  service,   is  available   principally  in
metropolitan  areas containing  approximately 44% of the nation's  population at
the end of 1997.  PCS carriers,  many of which offer short message  capabilities
and expect to offer  larger  capacity  packet data  services in the near future,
presently offer service which in the aggregate covers  approximately  60% of the
U.S. population.

Most cellular and PCS providers have structured  their services and distribution
principally to meet switched voice service  requirements of broad-market  users.
However, HighwayMaster Communications, Inc. offers data and voice communications
to the long-haul  trucking  industry  through the application of its proprietary
messaging and billing  technologies to circuit-switched  cellular capacity which
it purchases in bulk from a number of large  cellular  carriers.  Differences in
equipment  and service  pricing and  product  characteristics  result in minimal
direct competition  between the Company's voice products and most other cellular
carriers.

Specialized  Mobile  Radio (SMR) and  Enhanced  Specialized  Mobile Radio (ESMR)
Services.  Within the  limitations  of available  spectrum and  technology,  SMR
operators compete with the Company's voice dispatch services by providing mobile
communications  services,  including  mobile  telephone,  dispatch,  paging  and
limited  data  services.  For  certain  applications,  such as mobile  telephone
interconnect,  SMR  systems  presently  are less  expensive  than the  Company's
services,  although the shared channel  configuration and the economics of these
systems have traditionally caused SMR systems to be less frequently utilized for
voice telephone services.

SMR radio  services  have  been  expanding  rapidly  over the past ten years and
converting  from analog to digital  technology.  ESMR  systems  compete with the
Company's  voice  and data  dispatch  services  in  metropolitan  areas.  NEXTEL


                                     - 14 -

<PAGE>


Communications,  Inc.  ("Nextel")  provides  ESMR  services  in  numerous  large
metropolitan  service areas in the United States and is the leading  provider of
SMR using digital  technology,  frequency reuse and lower power  transmitters to
transform its current SMR service into cellular-like  services,  including voice
telephone services. Geotek Communications, Inc. ("Geotek") offers voice and data
communication  networks for the trunked mobile radio market.  Targeted primarily
to small and  medium-sized  businesses  managing  fleets of vehicles  and mobile
workforces,  Geotek is focused  on  providing  metropolitan  area voice and data
services. Currently, Geotek's service is available in 11 markets. Neither Nextel
nor Geotek  provide  nationwide  voice  dispatch or data services  comparable to
those offered by the Company.

Private  Land  Mobile  Frequencies.  Individual  companies  that have  chosen to
develop their own private wireless data network constitute a large percentage of
the wireless  marketplace for corporate fleets. An example of such a customer is
Federal Express. While these companies already have made significant investments
in their systems,  in some cases  recurring  maintenance,  upgrade and expansion
costs,  coupled with recent steps by the FCC to charge private system owners for
the use of the radio  frequencies,  have caused these  organizations  to turn to
commercial providers such as the Company.

Narrowband  PCS/Enhanced  Paging.  There are a large number of paging  companies
that offer messaging services on a regional or nationwide basis. Despite the low
cost  of  one-way  paging,  most  traditional  paging  services  do not  provide
full-function two-way  communications.  Although some paging companies,  such as
MTel,  have begun to offer  limited  time-delayed  two-way  messaging  services,
initial challenges in coverage,  responsiveness  and throughput  currently limit
their adoption by the Company's targeted business customers.

Mobile  Satellite   Services.   The  Company's  voice  and  data  services  face
competition  from a number  of  companies  that are  selling  or are  developing
services using a variety of satellite  technologies.  The principal  alternative
satellite-based  communications  system  available  to the  trucking  market  is
Qualcomm Incorporated's ("Qualcomm") OmniTracs nationwide data service. Qualcomm
currently  provides  low-speed  mobile data services using  terminals  which are
priced  competitively with the Company's  satellite-only  terminals.  Qualcomm's
OmniTracs  service  does  not  provide  a  terrestrial  communications  path  or
least-cost routing  capabilities similar to the Company's multi-mode product. As
a result,  transmissions to and from a vehicle must be routed exclusively over a
satellite  network  and are  subject  to  line  of  sight  blocking  and  higher
transmission costs, limiting the product's  functionality and cost-effectiveness
in segments that require urban coverage or large volumes of data transmission.

NORCOM Networks Inc.  ("NORCOM") is in the process of  commercially  deploying a
satellite-based  packet data  service  that  competes  with the  Company's  data
services in the  transportation  and field service  segments.  NORCOM  currently
purchases channel capacity on the Company's satellite over which it operates its
network,  and  combines its  satellite  data  service  product with  terrestrial
services provided by RAM and by the Company.

The Company's  satellite  services also compete for mobile maritime  subscribers
with TMI, a Canadian  company  operating a satellite  comparable to MSAT-2,  and
with Inmarsat, a consortium of 70 countries

                                     - 15 -

<PAGE>



that is authorized to provide  maritime  voice and data services along the North
American  coasts.  Because  Inmarsat's  current system  operates at a much lower
power level than does the  Company's  satellite,  its mobile  terminals  must be
equipped  with  antenna  systems that are larger and more  expensive  than those
required for the  Company's  network.  The  Inmarsat  system also has per minute
charges significantly higher than those charged by the Company. Comsat, the U.S.
signatory  for  Inmarsat,  applied to the FCC for  authority  to provide  mobile
satellite  services  ("MSS") in the United States through  Inmarsat  facilities.
TMI, which is technically capable of providing service within the United States,
has also  announced  its  intention  to provide MSS to domestic  customers  over
MSAT-1.  Although the FCC has  consistently  denied Comsat's  application,  most
recently on January 9, 1998, there can be no assurances that Comsat, TMI, or any
other  satellite  provider,  will not become  authorized  to provide  MSS in the
United States (See "Regulation").

Recently,  several  Low Earth  Orbit  ("LEO")  and Medium  Earth  Orbit  ("MEO")
satellite systems have been announced or have commenced deployment.  Examples of
these   systems,   which  are  more  complex  and  costly  than  the   Company's
geosynchronous network, include Iridium LLC; Globalstar Telecommunications, LTD,
and ICO Global. When deployed,  these systems will offer certain advantages over
the Company's  voice telephony  service,  including the ability to support small
handheld  telephones  and, in certain  instances,  reduced  transmission  delay.
However,  the  Company  does not  expect  that  these  systems  will  provide  a
nationwide  dispatch  service  or support  data  service in excess of 2,400 bps.
Moreover,  these companies are focused primarily on consumer-oriented and global
traveler  applications  and not the business  markets which are the focus of the
Company.  Further,  because these companies will deploy satellite systems,  they
are not expected to compete against urban  in-building data services provided by
the Company.

In addition to relatively  complex LEO systems  designed to provide mobile voice
services,  there are a number of proposals for  relatively  simple  "little" LEO
systems that would provide only low-speed  packet data services.  These systems,
including  ORBCOMM Global,  L.P., Final Analysis and LEO One USA, have access to
comparatively  limited  spectrum and are expected to compete for  customers  who
require  specialty  applications  such as asset tracking  services for unpowered
trailers.


                                   Regulation

American Mobile's satellite system and ARDIS' ground-based two-way wireless data
system are regulated to varying degrees at the federal, state, and local levels.
Various  legislative and regulatory  proposals under  consideration from time to
time by Congress and the FCC have in the past materially affected and may in the
future  materially  affect  the  telecommunications  industry  in  general,  and
American Mobile and ARDIS in particular. In addition, many aspects of regulation
at the federal,  state and local level  currently are subject to judicial review
or are the subject of administrative or legislative proposals to modify, repeal,
or adopt new laws and administrative  regulations and policies. The following is
a summary of significant laws,  regulations and policies affecting the operation
of American Mobile's and ARDIS' businesses.



                                     - 16 -

<PAGE>



General

The ownership and operation of American Mobile's system and ARDIS'  ground-based
two-way  wireless  data system are subject to the rules and  regulations  of the
FCC, which acts under authority  granted by the  Communications  Act and related
federal  laws.  Among  other  things,  the FCC  allocates  portions of the radio
frequency  spectrum to certain  services  and grants  licenses to and  regulates
individual  entities  using that  spectrum.  American  Mobile and ARDIS  operate
pursuant to various licenses granted by the FCC.

Both American  Mobile and ARDIS are  Commercial  Mobile Radio  Service  ("CMRS")
providers and therefore are  regulated as common  carriers.  The companies  must
offer service at just and reasonable rates on a first-come,  first-serve  basis,
without any unjust or unreasonable  discrimination,  and they are subject to the
FCC's complaint  processes.  The FCC has forborne from applying  numerous common
carrier provisions of the  Communications Act to CMRS providers.  In particular,
American  Mobile  and  ARDIS  are not  subject  to  traditional  public  utility
rate-of-return  regulation,  and the  companies are not required to file tariffs
with the FCC for their domestic services.

As providers of  interstate  telecommunications  services,  American  Mobile and
ARDIS are required to contribute  to the FCC's  universal  service  fund,  which
supports the provision of  telecommunications  services to high-cost  areas, and
establishes  funding  mechanisms to support the provision of service to schools,
libraries,  and rural  health care  providers.  Under the FCC's  current  rules,
American  Mobile and ARDIS are  required to  contribute  a  percentage  of their
end-user    telecommunications    revenues    resulting   from   the   sale   of
telecommunications services. The extent of this obligation is subject to change.
A number of parties  have  filed  petitions  for  review of the FCC's  universal
service  policy and these appeals have been  consolidated  in the U.S.  Court of
Appeals for the Fifth Circuit. Both companies may also be required to contribute
to state universal service programs. The requirement to make these payments, the
amount  of  which  in  some  cases  may be  subject  to  change  and is not  yet
determined,  may  have a  material  adverse  impact  on  the  conduct  of  their
businesses.

American Mobile and ARDIS are subject to the  Communications  Assistance for Law
Enforcement  Act ("CALEA").  Under CALEA,  American Mobile and ARDIS must ensure
that law enforcement agencies can intercept certain  communications  transmitted
over  their  networks.  American  Mobile  and ARDIS  must also  ensure  that law
enforcement  agencies are able to access  certain  call-identifying  information
relating to communications  over their networks.  The companies must comply with
the CALEA  requirements  and any rules  subsequently  promulgated by October 25,
1998 or face  possible  sanctions,  including  substantial  fines  and  possible
imprisonment of company officials.  The FCC currently has a proceeding  underway
to establish rules for the implementation of these requirements. This proceeding
primarily   addresses    record-keeping   and   security-related   issues.   The
telecommunications  industry,  which has been charged with establishing detailed
technical standards for compliance with CALEA's  requirements,  has not yet been
able to adopt final standards that are acceptable to law enforcement. While both
Congress and the FCC have the authority to extend the compliance deadline,  both
have thus far declined to do so. It is not clear whether the  companies  will be
able to comply with  CALEA's  requirements  or will be able to do so in a timely
manner.  CALEA  establishes  a  federal  fund to  compensate  telecommunications


                                     - 17 -

<PAGE>


carriers  for  all  reasonable  costs  directly  associated  with  modifications
performed by carriers in connection  with  equipment,  facilities,  and services
installed or deployed on or before January 1, 1995.  For equipment,  facilities,
and  services  deployed  after  January 1, 1995,  the CALEA fund is  supposed to
compensate  carriers for any  reasonable  costs  associated  with  modifications
required to make  compliance  "reasonably  achievable."  It is possible that all
necessary  modifications  will not  qualify for this  compensation  and that the
available  funds  will  not  be  sufficient  to  reimburse  the  companies.  The
requirement  to comply  with CALEA could have a material  adverse  effect on the
conduct of their businesses.

As a matter of general  regulation by the FCC, both of the companies are subject
to, among other things, payment of regulatory fees, restrictions on the level of
radio frequency  emissions of their systems' mobile terminals and base stations,
and "rate  integration"  regulations  requiring  that  providers  of  interstate
interexchange  telecommunications  services  charge  the same  rates  for  these
services in every state,  including Puerto Rico and the U.S. Virgin Islands. Any
of  these  regulations  may  have an  adverse  impact  on the  conduct  of their
businesses.

The FCC licenses of American Mobile and ARDIS are subject to restrictions in the
Communications  Act  that  (i)  certain  FCC  licenses  may  not  be  held  by a
corporation  of which more than 20% of its capital  stock is  directly  owned of
record or voted by non-U.S.  citizens or entities or their  representatives  and
(ii) that no such FCC license may be held by a corporation controlled by another
corporation   ("indirect  ownership")  if  more  than  25%  of  the  controlling
corporation's capital stock is owned of record or voted by non-U.S.  citizens or
entities or their representatives,  if the FCC finds that the public interest is
served  by the  refusal  or  revocation  of  such  license.  However,  with  the
implementation of the Basic  Telecommunications  Agreement  ("BTA"),  negotiated
under the  auspices  of the World  Trade  Organization  ("WTO") and to which the
United States is a party, the FCC will presume that indirect ownership interests
in excess of 25% by non-U.S.  citizens or entities  will be  permissible  to the
extent that the ownership interests are from WTO-member countries.  The BTA took
effect on February 5, 1998, and the FCC's  implementing  regulations took effect
on February 9, 1998.


American Mobile

American Mobile is licensed by the FCC to provide a broad range of mobile voice,
data and dispatch services via satellite to land, air and sea-based customers in
a service area  consisting of the  continental  United States,  Alaska,  Hawaii,
Puerto Rico,  the U.S.  Virgin  Islands and U.S.  coastal  waters and  airspace.
American Mobile is also authorized to provide fixed site voice and data services
via  satellite to locations  within this service  area, so long as such services
remain incidental to American Mobile's mobile communications services.  American
Mobile  is  authorized  to  build,  launch  and  operate  three   geosynchronous
satellites in accordance  with a specified  schedule.  American Mobile is not in
compliance with the schedule for commencement and construction of its second and
third satellites and has petitioned the FCC for changes to the schedule. Certain
of these extension requests have been opposed by third parties.  The FCC has not
acted on American  Mobile's  requests.  The FCC has the  authority to revoke the
authorizations  for the second and third satellites and, in connection with such


                                     - 18 -

<PAGE>


a revocation, could exercise its authority to rescind American Mobile's license.
American  Mobile  believes  that the  exercise of such  authority to rescind the
license is unlikely. The term of the license for each of American Mobile's three
authorized  satellites is ten years,  beginning when American  Mobile  certifies
that the respective  satellite is operating in compliance with American Mobile's
license.  The ten-year term of MSAT-2 began August 21, 1995.  Although  American
Mobile  anticipates  that the  authorizations  are likely to be  extended in due
course to correspond to the useful lives of the satellites and that new licenses
will be  granted  for  replacement  satellites,  there is no  assurance  of such
extension or grant.

American  Mobile's  current  foreign  ownership  level,  for which the  indirect
ownership limits are applicable,  is approximately 21%. Singapore,  which is the
domicile of Singapore Telecom, one of American Mobile's largest shareholders, is
a WTO-member country.

On March 12, 1998, the FCC granted American Mobile's application  requesting the
modification of its license to permit American Mobile to implement the Satellite
Purchase Agreement and Satellite Lease Agreement. This proceeding was contested,
and the  opponents  to this  application  may  seek  review  of this  grant.  In
addition,  this  grant  is  conditioned  upon and  subject  to  modification  as
necessary to comply with any subsequent agreement between representatives of the
governments of Canada and the United States concerning shared use of MSAT-1.

MSAT-2,   like   MSAT-1,   is   designed   to  be  able  to  operate   over  the
1530-1559/1631.5-1660.5  MHz bands (the "L-band").  American Mobile is currently
licensed to operate in the 1544-1559/1645-1660.5 MHz bands (the "upper L-band").
The  FCC has  designated  American  Mobile  as the  licensee  for  both  MSS and
Aeronautical  Mobile  Satellite  (Route) Service  ("AMS(R)S").  AMS(R)S includes
satellite communications related to air traffic control, as well as aeronautical
safety-related  operational and administrative  functions. As a condition to its
authorization, American Mobile is required by the FCC to be capable of providing
priority and preemptive access for AMS(R)S traffic in the upper L-band and to be
interoperable with and capable of transferring  AMS(R)S traffic to international
and  foreign  systems   providing  such  service.   American  Mobile   currently
anticipates  it will be able to meet these  requirements  without  any  material
adverse  effect on its  business.  If  American  Mobile is unable to meet  these
requirements,  the FCC may authorize and give priority spectrum access to one or
more additional satellite systems that meet the specified requirements.

American  Mobile has  applied  for  authorization  to operate in the  additional
1530-1544/1631.5-1645.5  MHz bands (the "lower  L-band").  If American Mobile is
assigned spectrum in the lower L-band, it will be required by the FCC to provide
similar priority and preemptive access in that spectrum to maritime distress and
safety  communications.  With  respect to its mobile voice  terminals,  American
Mobile currently  anticipates it will be able to meet this  requirement  without
any material adverse effect on its business. The Federal Aviation Administration
("FAA")  filed  comments,   however,   in  connection  with  American   Mobile's
application to operate up to 30,000 mobile data terminals that were transitioned
from leased space  segment to MSAT-2 in late 1995,  stating its concern that the
mobile data terminals  cannot be operated in compliance  with American  Mobile's
obligation to provide  priority and preemptive  access in the upper L-band.  The
FAA has proposed that American  Mobile  operate the mobile data terminals in the
lower  L-band.  American  Mobile has  received  successive  six-month  grants of
special temporary authority ("STA"),  under a two-year waiver of the FCC's rules
on priority and preemptive access, to operate up to 15,100 mobile data terminals
in the lower L-band.  This number was increased to 33,100 terminals  pursuant to
American  Mobile's  acquisition  of  the  mobile  data  equipment  and  services
previously licensed to Rockwell.  The two-year waiver expired on August 1, 1997,
but remains in effect while American  Mobile's request for a two-year  extension
of that  waiver is  pending at the FCC.  American  Mobile  will need  additional
authority to increase the number of mobile data  terminals that it is authorized
to operate if it is to fulfill contracts with GE Logisticom and others. American
Mobile will also need  permission  from the FCC to operate mobile data terminals
with a different transmission design than those operated under its current lower
L-band  authorization.  Transmissions  from these terminals require a wider band
width than do transmissions from American Mobile's existing terminals. There can
be no  assurance  that  American  Mobile will  continue to receive  authority to
operate  these new mobile data  terminals  or any other  additional  mobile data
terminals in the lower L-band.

American Mobile's mobile terminal  authorizations are subject to compliance with
certain requirements regarding interference protection to the Global Positioning
System ("GPS").  With the consent of the FAA, the FCC granted American  Mobile's
application  subject  to  certain  conditions,  including  that the grant may be
modified after the interference  issue is studied.  The FCC is now considering a
proposal from the National  Telecommunications and Information Administration to
impose more stringent  limits on the  out-of-band  emissions from certain mobile
terminals,  including those used in connection with American Mobile's system, in
order  to  protect  GPS and  the  Russian  Global  Navigation  Satellite  System
("Glonass").  This proposal would require that mobile terminals used on American
Mobile's  system be  manufactured  according  to a new design by 2002,  and that
existing  terminals  and any  terminals  not meeting the new  specifications  be
retired or retrofitted by 2005.  American  Mobile has opposed this proposal.  If
adopted by the FCC, this policy could have a material adverse effect on American
Mobile's business.

American Mobile's license  authorizes MSAT-2 to operate using certain telemetry,
transfer  and control  frequencies  in the  Ku-band,  and,  under the  Satellite
Purchase   Agreement,   American  Mobile  would  operate  MSAT-1  using  similar
frequencies.  American Mobile  operates  MSAT-2 at the 101 degrees W.L.  orbital
location, and, under the Satellite Purchase Agreement, would also operate MSAT-1
at 101 degrees  W.L. GE American  Communications,  Inc.  ("GE  American"),  also
operates a satellite at the 101 degrees W.L. orbital  location.  American Mobile
and GE  American  have an  agreement  covering  both  MSAT-1 and MSAT-2 that may
require  American Mobile to modify its operations or make certain payments to GE
American if  American  Mobile's  operations  cause  interference  to those of GE
American. While there can be no assurances,  the Company does not anticipate any
interference  in the  operations  of either  MSAT-1  or  MSAT-2  and those of GE
American.

American Mobile's  subscriber  equipment will operate in L-band frequencies that
are limited in  available  bandwidth.  The  feeder-link  earth  stations and the
network communications controller of the CGS operate in the more plentiful fixed
satellite  service  Ku-band  frequencies.  Of the 30  MHz  in the  upper  L-band
frequencies,   American   Mobile  is  currently   licensed  to  operate  in  the
1544-1559/1645.5-1660.5  MHz bands. Of the 30 MHz assigned to American Mobile by


                                     - 19 -

<PAGE>


the FCC,  one MHz is  limited  to  AMS(R)S  and  one-way  paging and two MHz are
limited to distress and safety communications.  American Mobile does not plan to
operate on these three MHz of bandwidth.

In June 1996, the FCC issued a notice of proposed rulemaking proposing to assign
to  American  Mobile  the  first 28 MHz of  internationally  coordinated  L-band
spectrum  from either the upper or lower  portion of the MSS  L-band.  Under the
FCC's  proposal,  American  Mobile would have first  priority  access to use the
lower L-band  spectrum as necessary to compensate for spectrum  unavailable  for
coordination  in the upper  L-band.  In the event the  United  States is able to
coordinate more than 28 MHz of L-band  spectrum,  the FCC has proposed  allowing
other applicants to apply for assignment of those frequencies.  Certain entities
have filed with the FCC  petitions to deny  American  Mobile's  application  and
comments  opposing the assignment of additional  frequencies to American Mobile.
While there can be no assurances,  American Mobile believes the FCC is likely to
grant American Mobile's application.

In the Ku-band  frequencies,  American  Mobile is currently  licensed to operate
MSAT-2 using 200 MHz within the bands 10.75-10.95 GHz for downlink transmissions
and 13.0-13.15 GHz and 13.2-13.25 GHz for uplink transmissions.  American Mobile
has applied for  authority to operate  using an  additional  200 MHz of spectrum
within the same bands.

Spectrum availability, particularly in the L-band, is a function not only of how
much spectrum is assigned to American  Mobile by the FCC, but also the extent to
which the same  frequencies  are used by other  systems  in the  North  American
region,  and the manner of such use. All spectrum use must be  coordinated  with
other  parties  that are  providing  or plan to provide  mobile  satellite-based
communications in the same geographical region using the same spectrum.  At this
time,  the other  parties with which  spectrum use must be  coordinated  include
Canada, Mexico, the Russian Federation and Inmarsat.

Use of the spectrum is determined  through a series of negotiations  between the
United States government and the other user agencies,  pursuant to the rules and
regulations of the International  Telecommunication  Union ("ITU"). For the past
several years, each of the countries and international  organizations  that have
used or will use L-band  frequencies  within the North American region have been
meeting  regularly to negotiate and  coordinate  their current and future use of
that spectrum.  American Mobile estimates that  international  coordination will
make  approximately 20 MHz of L-band spectrum available to the United States for
MSAT-2.  Since the  coordination  process  involves  many  parties  and there is
uncertainty about the total outcome, the actual amount of spectrum available may
be more or less than that estimated. In addition, the proposed Satellite Sharing
Agreement may make the  coordination  of spectrum for American  Mobile's  system
more  difficult.  Some of the spectrum that may be available to American  Mobile
may  include  a portion  of the 28 MHz lower  L-band  spectrum  adjacent  to the
frequencies already assigned to American Mobile by the FCC.

The ITU's  Radio  Regulations  include  a table of  frequency  allocations  that
prescribe  the  permitted  uses of the  radio  spectrum.  As a result of the ITU
satellite  plan for parts of the  Ku-band,  there  also may be  restrictions  on
American Mobile's ability to deploy feederlink earth stations in Alaska, Hawaii,
Puerto Rico, and the U.S. Virgin Islands.

                                     - 20 -

<PAGE>



During the course of the licensing process for American Mobile and several times
since,  the FCC has stated that there is only enough  spectrum in the MSS L-band
for the FCC to  authorize  a single MSS system to provide  service in the United
States.  In 1995,  however,  Comsat  applied for authority to provide MSS in the
United  States  in  the  L-band  over  the  Inmarsat  satellite  system.  Comsat
subsequently  filed an  application  seeking  a  blanket  authorization  for the
operation of 5,000 mobile  terminals in the United States,  as well as a request
for an STA to operate 50 mobile  terminals in the United  States.  On January 9,
1998, the FCC denied Comsat's  request for an STA and required that Comsat amend
its underlying applications to conform with the requirements  established in the
FCC's  November  1997  order on  market  access  by  foreign-licensed  satellite
systems.  This order  conforms the FCC's  regulations  with the BTA and makes it
easier for foreign  satellite  systems from  WTO-member  countries to access the
United States market,  while at the same time making clear that the FCC may deny
access  to such  satellite  applicants  on the basis of  spectrum  availability,
applicants'  technical,  legal,  or  financial  qualifications,  or  foreign  or
domestic policy  factors.  The order also requires Comsat to make an appropriate
waiver of immunity from any suit as part of any application to provide  domestic
services over Inmarsat's  system. On January 12, 1998, Comsat filed an appeal of
this order with the U.S.  Court of Appeals for the D.C.  Circuit,  and  American
Mobile is opposing  this appeal as an  intervenor.  On February 6, 1998,  Comsat
filed an  application  for review of the FCC's denial of its request for an STA,
and a petition  for waiver of the FCC's new market  access rules to permit it to
offer MSS on a temporary basis in the United States. American Mobile has opposed
these filings.

In its January 9, 1998 denial of Comsat's  STA  request,  the FCC stated that it
would be willing to authorize Comsat to provide  international service if Comsat
amended  its  blanket  license  application  to show that  service  through  its
terminals and Inmarsat's MSS system could be limited to  international  traffic.
Comsat has  amended  its  application  in order to make this  showing.  American
Mobile has  opposed  this  application.  In  addition,  Comsat has  applied  for
authority  under  Section  214 of the  Communications  Act to provide  satellite
paging and  tracking  services in the United  States.  American  Mobile has also
opposed this application.

TMI, which is technically capable of providing service within the United States,
has also  announced  its  intentions to provide MSS to domestic  customers  over
MSAT-1.  On  February  10,  1998,  the FCC  granted a  thirty-day  STA to SatCom
Systems,  Inc. for the testing of up to 30 mobile terminals in the United States
using TMI's system.  On March 10, 1998, SatCom filed a request for an additional
STA of 90 days for further  testing,  and also  requested that the scope of this
STA be expanded to permit it to operate up to 500 mobile  terminals for 180 days
on a private  carrier  so that it may  conduct  U.S.  marketing  trials.  SatCom
simultaneously  filed an  application  for a blanket  license  to  operate up to
25,000 mobile  terminals in the United States over MSAT-1 on a permanent  basis.
American Mobile will oppose  SatCom's  request for an expanded STA to operate up
to 500 mobile  terminals  for 180 days and SatCom's  application  for  permanent
authority to operate mobile terminals in the United States.

On January 30, 1998, Kitcomm Satellite  Communications Ltd.  ("Kitcomm") filed a
letter of intent with the FCC to provide MSS to U.S. customers over its proposed
foreign-licensed  satellite  system.  Kitcomm proposes to provide two-way remote
data  collection,  tracing,  and messaging  services over a global system in the

                                     - 21 -

<PAGE>

lower L-band at 1525-1530/1626.5-1631 MHz. In order to provide domestic service,
Kitcomm will also have to request  authority to operate mobile  terminals in the
United States.  American  Mobile will oppose any FCC application by Kitcomm that
would reduce the spectrum  available to American  Mobile either directly or as a
result of international frequency coordination.

In addition to providing  additional  competition to American Mobile, a grant of
domestic   authority  by  the  FCC  to  one  of  these  foreign   systems  would
significantly increase the demand for spectrum in the international coordination
process and could adversely affect American Mobile's business.

American  Mobile is operating  under waivers of certain FCC rules.  In 1996, the
FCC  issued an order  requiring  all CMRS  providers  to offer what are known as
"enhanced  9-1-1  services"  including the ability to  automatically  locate the
position of all transmitting  mobile  terminals.  American Mobile would not have
been  able  to  offer  this  automatic  location   information   without  adding
substantially  to the cost of its mobile  equipment  and  reconfiguring  its CGS
software.  The FCC  decided  not to  impose  specific  new  requirements  on MSS
providers,  including  American  Mobile,  at that  time.  The FCC did  state its
expectation  that  such  providers  eventually  would  be  required  to  provide
"appropriate   access  to  emergency   services."  A  decision  to  impose  this
requirement  on MSS providers  could have a material  adverse effect on American
Mobile.

The FCC enacted  "rate  integration"  regulations  requiring  that  providers of
interstate interexchange  telecommunications  services charge the same rates for
these  services  in every  state,  including  Puerto  Rico  and the U.S.  Virgin
Islands.  American  Mobile has opposed the  imposition of this rate  integration
requirement on its MSS system, so that it may preserve the flexibility to charge
more for service in areas covered by satellite beams that require more satellite
power. The FCC has denied American  Mobile's  request for a permanent  exemption
from  its  rate  integration  requirement,  but has not yet  ruled  on  American
Mobile's  request for a temporary  waiver of a year or more. The FCC has granted
American Mobile an interim waiver from its rate  integration  requirement  until
its decision on American Mobile's temporary waiver request.


ARDIS

ARDIS' wireless data network consists of base stations  licensed in the Business
Radio  and  Specialized  Mobile  Radio  Service,  all  operating  in the 800 MHz
frequency  band.  The ARDIS system is  interconnected  with the public  switched
network.

The FCC's licensing regime in effect when it issued ARDIS' licenses provided for
the issuance of  individual  licenses for specific  channels at specific  sites.
With  respect  to the part of the  band in which  all of  ARDIS'  base  stations
operate,  however,  the FCC has  implemented  a new  licensing  regime.  The new
licensing  regime involves the auctioning of licenses for specific  channels for
wide  geographic  areas,   within  which  the  licensee  will  have  substantial
flexibility to operate any number of base stations, including base stations that
may operate on the same channels as incumbent  licensees such as ARDIS.  The FCC
has proposed to conduct the auctions for additional channel capacity of the kind


                                     - 22 -

<PAGE>


used by ARDIS  beginning  in the third  quarter  of 1998.  The FCC  proposes  to
prohibit the new geographic  licensees from causing  interference to incumbents,
but there is  concern  that  such  interference  may  occur  and that  practical
application of these rules is uncertain.

ARDIS believes that it has licenses for sufficient  channels to meet its current
needs for capacity.  To the extent that it needs additional capacity,  it may be
required to either participate in the upcoming auctions or acquire channels from
other  licensees.  As part of its  new  licensing  regime,  the  FCC  permits  a
wide-area geographic licensee, with prior FCC approval, to sell a portion of its
geographic  area to another  entity.  This  partitioning  authority may increase
ARDIS'  flexibility  to operate  additional  base  stations,  but the  practical
utility of this option is uncertain at this time.

ARDIS  operates  its system  under a number of  waivers  of the FCC's  technical
rules,  including  rules on  station  identification,  for-profit  use of excess
capacity,  system  loading,  and multiple  station  ownership.  Several of these
waivers were first  obtained  individually  by IBM and Motorola,  which operated
separate  wireless  data systems  until forming the ARDIS joint venture in 1990.
The FCC  incorporated  a number of these  waivers into its  regulations  when it
implemented Congress' statutory provision creating the CMRS classification,  and
ARDIS no longer  requires  those  waivers.  On June 5, 1996,  the FCC waived its
one-year  construction  requirement  and  granted  ARDIS  extensions  of time to
complete  the  buildouts  of  approximately  190 sites,  as required to maintain
previously granted licenses.  As of March 25, 1998, ARDIS intends but has yet to
construct 104 of these sites. The extended  construction  deadlines vary by site
between June 27, 1998 and March 31, 1999. Failure to complete the buildouts in a
timely manner could result in a loss of licenses for such sites from the FCC. In
addition, at 11 of 104 uncompleted sites ARDIS is required to erect a new tower,
and there is no  assurance  that local  zoning  regulations  will not affect the
timetable for the completion of these sites.

The  foregoing  does not purport to describe all present and  proposed  federal,
state, and local regulation and legislation  relating to the industries in which
American  Mobile and ARDIS operate.  Other existing  federal,  state,  and local
regulations  currently  are the  subject of a variety of  judicial  proceedings,
legislative  hearings,  and administrative and legislative  proposal which could
change,  in  varying  degrees,  the  manner in which  American  Mobile and ARDIS
operate.  Neither the outcome of these  proceedings nor their impact on American
Mobile's and ARDIS' operations can be predicted at this time.


ARDIS Acquisition

On March 3, 1998,  the FCC granted  authority for the transfer of control of all
authorizations  held by ARDIS  to the  Company,  thereby  permitting  ARDIS  and
American  Mobile to consummate the  Acquisition.  Interested  parties have until
April 2, 1998 to appeal or ask for  reconsideration  of this grant,  and the FCC
has until April 13, 1998 to  reconsider  this grant on its own motion.  If these
dates are reached  without any challenge or FCC  reconsideration  of this grant,
this grant will become  final and not  subject to appeal.  In the event that the
FCC  takes  action  that  prevents  American  Mobile  from  operating  ARDIS  as
contemplated,  American  Mobile has the right to  rescind  the  Acquisition  (an


                                     - 23 -

<PAGE>


"Unwind") by providing  notice to Motorola within 30 days of the receipt of such
adverse order.  In the event of an Unwind,  the Purchase Price would be returned
to American Mobile and American Mobile's  ownership  interests in ARDIS would be
returned to  Motorola.  While the Company  does not believe  that such an Unwind
will  occur,  were it to occur,  such an Unwind  would have a  material  adverse
effect on the Company.


                              Year 2000 Compliance

The Company has  implemented  a Year 2000  program to ensure that the  Company's
computer systems, applications,  subscriber units, communications processors and
back office support systems will function  properly beyond 1998. The Company has
assessed how it may be impacted by Year 2000 and has  formulated  and  commenced
implementation of a comprehensive plan to address known issues as they relate to
its information systems.  Vendors that provide critical products and services to
the Company are included in this  assessment  plan.  The plan,  as it relates to
information  systems,  includes  a  combination  of  modification,  upgrade  and
replacement.


If necessary  modifications  and conversions by the Company and those with which
it  conducts  business  are  not  completed  in  a  timely  manner,   Year  2000
non-compliance  may have a material adverse effect on the Company's  operations.
While there can be no  assurances,  the Company  estimates that the cost of Year
2000  compliance  for its  information  system will not have a material  adverse
effect on the future consolidated  results of the operations of the Company. The
Company  is not yet able to  estimate  the  cost of Year  2000  compliance  with
respect  to third  party  suppliers;  however,  based on a  preliminary  review,
management  does not expect that such costs will have a material  adverse effect
on the Company's financial condition, results of operations and cash flow.


                                    Employees

At March 31, 1998,  the Company had  approximately  477  employees.  None of the
Company's  employees is represented by a labor union. The Company  considers its
relations with its employees to be good.

                                     - 24 -

<PAGE>



Item 2.  Properties.

The Company leases  approximately  94,000 square feet at its headquarters office
space and network  operations center in Reston,  Virginia.  The lease has a term
which runs  through  August 3, 2003  (which  may be  extended  at the  Company's
election for an  additional  five  years).  In  addition,  the Company  leases a
back-up Ku-band radio frequency  facility in Alexandria,  Virginia.  The Company
also leases  approximately  86,000 square feet of space for an operations center
in  Lincolnshire,  Illinois,  the lease for which expires December 31, 2000, and
approximately 7,800 square feet for a remote data center in Lexington, Kentucky,
the lease for which expires  April 30, 2001.  The Company also leases site space
for approximately 1,700 base stations across the country under one- to five-year
lease contracts with renewal provisions. The Company anticipates that it will be
able to  gain  access  to  additional  base  station  sites  when  necessary  on
acceptable terms.


Item 3.  Legal Proceedings.

In 1992, a former director of American Mobile filed an Amended Complaint against
American Mobile alleging violations of the Communications Act and of the Sherman
Act and  breach  of  contract.  The suit  seeks  damages  for not less than $100
million  trebled  under the  antitrust  laws plus  punitive  damages,  interest,
attorneys'  fees and costs.  In  mid-1992,  American  Mobile  filed its response
denying all allegations. American Mobile's motion for summary judgment, filed on
June 30,  1994,  was  denied  on  April  18,  1996.  The  trial in this  matter,
previously  set for December 1997, has been postponed to a date to be determined
in 1998.  Management  believes  that the  complaint  is without  merit,  and the
ultimate outcome of this matter will not be material to the Company's  financial
position, results of operations, or its cash flow.


Item 4.  Submission of Matters to a Vote of Security Holders.

No matters were  submitted to a vote of the  Company's  Stockholders  during the
fourth quarter of fiscal 1997.




                                     - 25 -

<PAGE>





                                     PART II

Items 5, 6, 7 and 8.

The  information  called for by Items 5 through 8 of Part II is  presented  in a
separate  section  of this  Annual  Report on Form 10-K  commencing  on the page
numbers specified below:

Form 10-K Item                                                        Page

Item 5 - Market for the Registrant's 
          Common Equity and Related Matters                           F-49

Item 6 - Selected Financial Data                                      F-50

Item 7- Management's Discussion and Analysis 
         of Financial Condition and Results of Operations             F-1

Item 8 - Financial Statements and Supplementary Data                  F-15



Item 9.  Changes in and Disagreements with Accountants on Accounting and
         Financial Disclosure.

None.




                                     - 26 -

<PAGE>



                                    PART III


Items 10, 11, 12 and 13.

The information called for by Part III (Items 10, 11, 12 and 13) is incorporated
herein by reference from the material  included  under the captions  "Nominees,"
"Executive Officers," "Executive  Compensation,"  "Security Ownership of Certain
Beneficial   Owners   and   Management,"    "Agreements   Among   Stockholders,"
"Compensation and Stock Option Committee  Interlocks and Insider  Participation"
and "Section 16(a) Beneficial  Ownership Reporting  Compliance" in the Company's
definitive  proxy statement (to be filed) for its Annual Meeting of Stockholders
to be held May 20, 1998 (the "Proxy  Statement").  The Proxy  Statement is being
prepared and will be filed with the Securities and Exchange  Commission pursuant
to  Regulation  14A on or about April 10, 1998,  and  furnished to the Company's
Stockholders, on or about April 25, 1998.




                                     - 27 -

<PAGE>





                                     PART IV

Item 14.  Exhibits, Financial Statement Schedules, and Reports on Form 8-K.


(a)  1.  Financial Statements.

The  following   consolidated  financial  statements  of  the  Company  and  its
subsidiaries  are included in a separate  section of this Annual  Report on Form
10-K commencing on the page numbers specified below:


INDEX

Management's Discussion and Analysis of Financial Condition
          and Results of Operations.......................................F - 1

Report of Independent Public Accountants..................................F - 15

Consolidated Statements of Loss...........................................F - 16

Consolidated Balance Sheets...............................................F - 17

Consolidated Statements of Stockholders' Equity...........................F - 18

Consolidated Statements of Cash Flows.....................................F - 19

Notes to Consolidated Financial Statements................................F - 20

Quarterly Financial Data..................................................F - 49

Selected Financial Data...................................................F - 50




                                     - 28 -

<PAGE>



         2.  Financial Statement Schedules.

Financial  Statement  Schedules not included with the one listed below have been
omitted because they are not required or not applicable, or because the required
information is shown in the financial statements or notes thereto.

         I.   Condensed Financial
              Information of Registrant.................................Page S-1




         2.   Exhibits

         3.1     -  Restated  Certificate of  Incorporation of AMSC (as restated
                    effective May 1, 1996) (Incorporated by reference to Exhibit
                    3.1a to the  Company's  Quarterly  Report on Form 10-Q filed
                    for the  periods  ending  March 31,  1996 and June 30,  1996
                    (File No. 0-23044))

         3.2     -  Amended and Restated Bylaws of AMSC (as amended and restated
                    effective  February 29,  1996)(Incorporated  by reference to
                    Exhibit 3.2 to the Company's  Quarterly  Report on Form 10-Q
                    filed for the period ending June, 1996 (File No. 0- 23044))

         9.1     -  Amended and  Restated  Stockholders'  Agreement  dated as of
                    December 1, 1993,  between  AMSC and certain  holders of its
                    capital stock  (Incorporated  by reference to Exhibit 9.1 to
                    the Company's  Registration  Statement on Form S-1 (Reg. No.
                    33- 70468))  10.3 - Contract for an MSAT  Spacecraft,  dated
                    December 7, 1990 between AMSC and Hughes  Aircraft  Company,
                    amended  June 15,  1993  (Amendment  Nos.  1 through  4) and
                    further amended November 11, 1993 (Amendment No. 5), between
                    AMSC Subsidiary Corporation, as assignee of AMSC, and Hughes
                    Aircraft Company  (Incorporated by reference to Exhibit 10.3
                    to the  Company's  Registration  Statement on Form S-1 (Reg.
                    No. 33-70468))

         10.3a   -  Amendment No. 6 to the AMSC Hughes MSAT Spacecraft Contract,
                    dated October 11, 1994, between AMSC Subsidiary Corporation,
                    as   assignee   to  AMSC,   and  Hughes   Aircraft   Company
                    (Incorporated by reference to Exhibit 10.3a to the Company's
                    Annual  Report  on Form  10-K  for  the  fiscal  year  ended
                    December 31, 1994 (File No. 0-23044))


                                     - 29 -

<PAGE>



         10.3b  -   Mutual Final Release,  dated October 11, 1994,  between AMSC
                    Subsidiary  Corporation,  Hughes  Aircraft,  Spar  Aerospace
                    Limited  and  Lockheed   Missiles  &  Space  Company,   Inc.
                    (Incorporated by reference to Exhibit 10.3b to the Company's
                    Annual  Report  on Form  10-K  for  the  fiscal  year  ended
                    December 31, 1994 (File No. 0-23044))

         10.3c   -  Amendment No. 7 to the AMSC Hughes MSAT Spacecraft Contract,
                    dated October 11, 1994, between AMSC Subsidiary Corporation,
                    as  assignee to AMSC,  and Hughes  Aircraft  Company  (filed
                    herewith)

         10.7    -  Memorandum  of  Agreement  for  Satellite  Capacity,   dated
                    February 17, 1992,  between AMSC Subsidiary  Corporation and
                    Telesat Mobile Inc., as amended by Amending  Agreement dated
                    October 18, 1993 among AMSC, AMSC Subsidiary Corporation and
                    TMI  Communications  and Company,  Limited  Partnership,  as
                    successor in interest to Telesat Mobile Inc., and as further
                    amended  by  letter   agreement   dated   October  18,  1993
                    (Incorporated  by reference to Exhibit 10.7 to the Company's
                    Registration Statement on Form S-1 (Reg. No. 33-70468))

         10.11   -  Right of First Offer Agreement dated as of November 30, 1993
                    among AMSC, Hughes Communications  Satellite Services, Inc.,
                    Singapore  Telecommunications Ltd., Satellite Communications
                    Investments  Corporation,  Space  Technologies  Investments,
                    Inc.,  Satellite  Mobile  Telephone  Company  L.P.,  Transit
                    Communications, Inc., MTel Space Technologies, L.P. and MTel
                    Space Technologies Corporation (Incorporated by reference to
                    Exhibit  10.11 to the  Company's  Registration  Statement on
                    Form S-1 (Reg. No. 33-70468))

         10.13*  -  Amended and Restated Stock Option Plan (as amended effective
                    May 21, 1997) (Incorporated by reference to Exhibit 10.13 to
                    the  Company's  Registration  Statement  on Form  S-8  (Reg.
                    No.333-30099))

         10.13b* -  Amended   Form   of   Employee   Stock   Option    Agreement
                    (Incorporated by reference to Exhibit 10.3b to the Company's
                    Annual  Report  on Form  10-K  for  the  fiscal  year  ended
                    December 31, 1994 (File No. 0-23044))

         10.13c* -  Form of Restricted Stock Agreement (filed herewith)

         10.1    -  [Reserved.]

         10.15   -  [Reserved.]

         10.16   -  [Reserved.]


                                     - 30 -

<PAGE>



         10.17   -  Mobile Terminal Production Agreement, dated October 6, 1992,
                    between  AMSC  Subsidiary   Corporation   and   Westinghouse
                    Electric Corporation acting through Westinghouse  Electronic
                    Systems Company  (Incorporated by reference to Exhibit 10.17
                    to the  Company's  Registration  Statement on Form S-1 (Reg.
                    No. 33-70468))

         10.17a  -  Amendment  No. 1 to Mobile  Terminal  Production  Agreement,
                    dated November 21, 1994, between AMSC Subsidiary Corporation
                    and  Westinghouse   Electric   Corporation   acting  through
                    Westinghouse  Electronic  Systems Company  (Incorporated  by
                    reference to Exhibit  10.17a to the Company's  Annual Report
                    on Form 10-K for the fiscal  year ended  December  31,  1994
                    (File No. 0-23044))

         10.17b  -  Amendment  No. 2 to Mobile  Terminal  Production  Agreement,
                    dated January 23, 1995, between AMSC Subsidiary  Corporation
                    and  Westinghouse   Electric   Corporation   acting  through
                    Westinghouse  Electronic  Systems Company  (Incorporated  by
                    reference to Exhibit  10.17b to the Company's  Annual Report
                    on Form 10-K for the fiscal  year ended  December  31,  1994
                    (File No. 0-23044))

         10.17c  -  Amendment  No. 3 to Mobile  Terminal  Production  Agreement,
                    dated March 21, 1995,  between AMSC  Subsidiary  Corporation
                    and  Westinghouse   Electric   Corporation   acting  through
                    Westinghouse  Electronic  Systems Company  (Incorporated  by
                    reference to Exhibit  10.17c the Company's  Annual Report on
                    Form 10-K for the fiscal year ended  December 31, 1994 (File
                    No. 0-23044))

         10.18   -  Mobile  Terminal  Production  Contract,  dated  November 30,
                    1992,  between AMSC  Subsidiary  Corporation  and Mitsubishi
                    Electric  Corporation  (Incorporated by reference to Exhibit
                    10.18 to the  Company's  Registration  Statement on Form S-1
                    (Reg. No. 33-70468))

         10.18a  -  Addendum  Number One dated June 29, 1994, to Mobile Terminal
                    Production Contract between AMSC Subsidiary  Corporation and
                    Mitsubishi Electric  Corporation  (Incorporated by reference
                    to Exhibit 10.18a to the Company's  Quarterly Report on Form
                    10-Q  filed  for the  period  ending  June  30,  1994  (File
                    No.0-23044))

         10.18b  -  Memorandum of Agreement,  dated  November 30, 1994,  between
                    AMSC   Subsidiary   Corporation   and  Mitsubishi   Electric
                    Corporation  (Incorporated by reference to Exhibit 10.18b to
                    the Company's Annual Report on Form 10-K for the fiscal year
                    ended December 31, 1994 (File No. 0-23044))

         10.19   -  Codec License Agreement,  dated February 2, 1993 and amended
                    March 26, 1993,  between  AMSC  Subsidiary  Corporation  and
                    Digital Voice Systems,  Inc.  (Incorporated  by reference to
                    Exhibit  10.19 to the  Company's  Registration  Statement on
                    Form S-1 (Reg. No. 33-70468))


                                     - 31 -

<PAGE>



                   
         10.20   -  Deed of Lease at Reston,  Virginia,  dated  February 4, 1993
                    and  amended   June  21,  1993,   between  AMSC   Subsidiary
                    Corporation  and  Trust  Company  of  the  West  as  Trustee
                    (Incorporated by reference to Exhibit 10.20 to the Company's
                    Registration Statement on Form S-1 (Reg. No. 33-70468))

         10.20a  -  Amendment  No. 4 to Deed of Lease,  dated  October  7, 1994,
                    between AMSC Subsidiary Corporation and Trust Company of the
                    West as Trustee (Incorporated by reference to Exhibit 10.20a
                    to the  Company's  Annual Report on Form 10-K for the fiscal
                    year ended December 31, 1994 (File No. 0-23044))

         10.21   -  Authorized Service Provider Agreement,  dated March 1, 1993,
                    between  AMSC  Subsidiary  Corporation  and  McCaw  Cellular
                    Communications,  Inc.  (Incorporated by reference to Exhibit
                    10.21 to the  Company's  Registration  Statement on Form S-1
                    (Reg. No. 33-70468))

         10.23   -  Term  Loan  Agreement  dated  May  28,  1993,  between  AMSC
                    Subsidiary   Corporation   and  Northern   Telecom   Finance
                    Corporation,  amended by letter  agreement dated October 14,
                    1993  between  AMSC  Subsidiary   Corporation  and  Northern
                    Telecom Finance  Corporation.  (Incorporated by reference to
                    Exhibit  10.23 to the  Company's  Registration  Statement on
                    Form S-1 (Reg. No. 33-70468))

         10.23a  -  First  Amendment to Term Loan Agreement dated as of April 8,
                    1994,  between  AMSC  Subsidiary  Corporation  and  Northern
                    Telecom Finance  Corporation  (Incorporated  by reference to
                    Exhibit  10.23a to the  Company's  Quarterly  Report on Form
                    10-Q filed for the  period  ending  June 30,  1994 (File No.
                    0-23044))

         10.23b  -  Second  Amendment  to Term Loan  Agreement,  dated August 1,
                    1995,  between  AMSC  Subsidiary  Corporation  and  Northern
                    Telecom Finance  Corporation.  (Incorporated by reference to
                    Exhibit  10.23b to the  Company's  Quarterly  Report on Form
                    10-Q filed for the period  ending  September  30, 1995 (File
                    No. 0-23044))

         10.23c  -  Third  Amendment to Term Loan  Agreement,  dated November 7,
                    1995,  between  AMSC  Subsidiary  Corporation  and  Northern
                    Telecom Finance  Corporation  (Incorporated  by reference to
                    Exhibit  10.23c to the  Company's  Quarterly  Report on Form
                    10-Q filed for the period  ending  September  30, 1996 (File
                    No. 0-23044))


                                     - 32 -

<PAGE>



         10.23d  -  Fourth  Amendment to Term Loan  Agreement,  dated October 1,
                    1996,  between  AMSC  Subsidiary  Corporation  and  Northern
                    Telecom Finance  Corporation  (Incorporated  by reference to
                    Exhibit  10.23d to the  Company's  Quarterly  Report on Form
                    10-Q filed for the period  ending  September  30, 1996 (File
                    No. 0-23044))

         10.23e  -  Fifth Amendment to Term Loan  Agreement,  dated December 19,
                    1997,  between AMSC Subsidiary  Corporation and NTFC Capital
                    Corporation  (formerly  known as  Northern  Telecom  Finance
                    Corporation) (filed herewith)

         10.24a  -  Volume Purchasing  Agreement,  dated March 10, 1995, between
                    AMSC  Subsidiary  Corporation  and  TNL  Navigation  Limited
                    (Incorporated   by  reference  to  Exhibit   10.24a  to  the
                    Company's  Annual  Report on Form 10-K for the  fiscal  year
                    ended December 31, 1994 (File No. 0-23044))

         10.24b  -  First Amendment to Volume Purchasing Agreement,  dated March
                    10,  1995,  between  Trimble  Navigation  Limited  and  AMSC
                    (Incorporated   by  reference  to  Exhibit   10.24b  to  the
                    Company's  Annual  Report on Form 10-K for the  fiscal  year
                    ended December 31, 1996 (File No. 0-23044))

         10.24c  -  Second  Amendment  to  Volume  Purchasing  Agreement,  dated
                    January 28, 1997,  between  Trimble  Navigation  Limited and
                    AMSC  (Incorporated  by reference  to Exhibit  10.24c to the
                    Company's  Annual  Report on Form 10-K for the  fiscal  year
                    ended December 31, 1996 (File No. 0-23044))

         10.24d  -  Third Amendment to Volume Purchasing Agreement, dated August
                    29, 1997, between Trimble Navigation Limited and AMSC (filed
                    herewith)

         10.25   -  Master Lease  Agreement,  dated June 23, 1993,  between AMSC
                    Subsidiary Corporation and Digital Equipment Corporation and
                    Amendment to Master Lease Agreement  between AMSC Subsidiary
                    Corporation and Digital  Equipment  Corporation dated August
                    2, 1993  (Incorporated  by reference to Exhibit 10.25 to the
                    Company's  Registration  Statement  on Form  S-1  (Reg.  No.
                    33-70468))

         10.26   -  [Reserved]

         10.27   -  Telemetry, Tracking and Control Satellite Service Agreement,
                    dated  as  of  August  5,  1993,   between  AMSC  Subsidiary
                    Corporation and Hughes  Communications  Satellite  Services,
                    Inc.  (Incorporated  by  reference  to Exhibit  10.27 to the
                    Company's  Registration  Statement  on Form  S-1  (Reg.  No.
                    33-70468))

         10.28   -  [Reserved]

                                     - 33 -

<PAGE>



         10.29   -  [Reserved]

         10.30   -  Agreement  dated  October  11,  1993,  among  AMSC,   Hughes
                    Communications    Satellite   Services,    Inc.,   Singapore
                    Telecommunications  Ltd.,  Space  Technologies  Investments,
                    Inc.,  MTel Space  Technologies  Corporation  and MTel Space
                    Technologies,  L.P.  (Incorporated  by  reference to Exhibit
                    10.30 to the  Company's  Registration  Statement on Form S-1
                    (Reg. No. 33-70468))

         10.31   -  [Reserved]

         10.32   -  Agreement  for  Cooperation  in  Joint  Procurement  of  MSS
                    Systems,  dated September 19, 1988,  between American Mobile
                    Satellite   Consortium   Inc.   and   Telesat   Mobile  Inc.
                    (Incorporated by reference to Exhibit 10.32 to the Company's
                    Registration Statement on Form S-1 (Reg. No. 33-70468))

         10.33   -  Joint  Operating  Agreement,  dated April 25, 1990,  between
                    AMSC  and  Telesat   Mobile  Inc.  as  amended  by  Amending
                    Agreement dated October 18, 1993 among AMSC, AMSC Subsidiary
                    Corporation  and TMI  Communications  and  Company,  Limited
                    Partnership, as successor in interest to Telesat Mobile Inc.
                    (Incorporated by reference to Exhibit 10.33 to the Company's
                    Registration Statement on Form S-1 (Reg. No. 33-70468))

         10.34*  -  Employee Stock Purchase Plan  (Incorporated  by reference to
                    Exhibit  10.34 to the  Company's  Registration  Statement on
                    Form S-1 (Reg. No. 33-70468))

         10.35   -  Agreement  dated  as  of  December  14,  1992  between  AMSC
                    Subsidiary   Corporation   and  GTE   Spacenet   Corporation
                    (Incorporated by reference to Exhibit 10.35 to the Company's
                    Registration Statement on Form S-1 (Reg. No. 33-70468))

         10.35a  -  Amendment  No.  1  dated  as of  November  7,  1997  to  the
                    Agreement  dated as of December  14,  1992,  by GTE Spacenet
                    Corporation and AMSC Subsidiary Corporation (filed herewith)

         10.36a  -  Master  Agreement dated March 30, 1994,  between  Washington
                    International  Teleport,  Inc.,  and AMSC  (Incorporated  by
                    reference to Exhibit  10.36a to the Company's  Annual Report
                    on Form 10-K for the fiscal  year ended  December  31,  1993
                    (File No. 0-23044))

         10.36b  -  Contract  Amendment  No. A001,  dated July 1, 1994,  between
                    Washington    International   Teleport,   Inc.,   and   AMSC
                    (Incorporated   by  reference  to  Exhibit   10.36b  to  the
                    Company's Quarterly Report on Form 10-Q filed for the period
                    ending September 30, 1994 (File No. 0-23044))


                                     - 34 -

<PAGE>



                   
         10.36c  -  Contract  Amendment  No. A002,  dated July 1, 1994,  between
                    Washington    International   Teleport,   Inc.,   and   AMSC
                    (Incorporated   by  reference  to  Exhibit   10.36c  to  the
                    Company's Quarterly Report on Form 10-Q filed for the period
                    ending September 30, 1994 (File No. 0-23044))

         10.37   -  [Reserved.]

         10.3    -  [Reserved.]

         10.39   -  [Reserved.]

         10.40   -  [Reserved.]

         10.41*  -  Form of  Directors  and Officers  Indemnification  Agreement
                    (Incorporated by reference to Exhibit 10.41 to the Company's
                    Annual  Report  on Form  10-K  for  the  fiscal  year  ended
                    December 31, 1993 (File No. 0-23044))

         10.42   -  DTE Design, Development,  and Manufacturing Agreement, dated
                    September 28, 1994, between AMSC Subsidiary  Corporation and
                    Omnidata  International,  Inc. (Incorporated by reference to
                    Exhibit  10.42 to the  Company's  Annual Report on Form 10-K
                    for the  fiscal  year  ended  December  31,  1994  (File No.
                    0-23044))

         10.43   -  [Reserved.]

         10.44   -  CAL  Corporation   Agreement  for  the  development  of  the
                    aeronautical MSAT terminal, dated December 22, 1994, between
                    AMSC    Subsidiary    Corporation    and   CAL   Corporation
                    (Incorporated by reference to Exhibit 10.44 to the Company's
                    Annual  Report  on Form  10-K  for  the  fiscal  year  ended
                    December 31, 1994 (File No. 0- 23044))

         10.45   -  Contract  for System  Enhancement,  dated  February 1, 1994,
                    between  AMSC  Subsidiary   Corporation   and   Westinghouse
                    Electric Corporation acting through Westinghouse  Electronic
                    Systems Company  (Incorporated by reference to Exhibit 10.45
                    to the  Company's  Annual Report on Form 10-K for the fiscal
                    year ended December 31, 1994 (File No. 0-23044))

         10.46   -  Agreement for the Manufacture,  Delivery and Installation of
                    Satellite Communications Equipment Supporting 6 TDMs per LES
                    and working to AMSC  Satellite,  dated  November  21,  1994,
                    between Hughes Network  Systems  Limited and AMSC Subsidiary
                    Corporation  (Incorporated  by reference to Exhibit 10.46 to
                    the Company's Annual Report on Form 10-K for the fiscal year
                    ended December 31, 1994 (File No. 0-23044))

                                     - 35 -

<PAGE>



                    
         10.46a  -  Amendment One to Agreement Number 742-94, dated December 15,
                    1994,  between  Hughes  Network  Systems  Limited  and  AMSC
                    Subsidiary Corporation (Incorporated by reference to Exhibit
                    10.46a to the  Company's  Annual Report on Form 10-K for the
                    fiscal year ended December 31, 1994 (File No. 0-23044))

         10.47   -  [Reserved.]

         10.48   -  [Reserved.]

         10.49   -  General   Services   Agreement   between   AMSC   Subsidiary
                    Corporation  and  AT&T  Corp.,  acting  though  its  Network
                    Systems Group, dated April 4, 1995 (certain attachments have
                    not been  provided and will be  furnished to the  Commission
                    upon request) (Incorporated by reference to Exhibit 10.49 to
                    the  Company's  Quarterly  Report on Form 10-Q filed for the
                    period ending June 30, 1995 (File No. 0-23044))

         10.51   -  Agreement  for  Development  of  High-Gain  Maritime  Mobile
                    Terminals  between  AMSC  and  KVH  Industries,  Inc.  dated
                    September  19, 1995.  (Incorporated  by reference to Exhibit
                    10.51 to the Company's  Annual Report on Form 10-K filed for
                    the period ended December 31, 1996 (File No. 0-23044))

         10.52   -  Private Voice Network Service,  Satellite Telephone Service,
                    Facsimile,  and  Circuit  Switched  Data  Service  Agreement
                    between AMSC and AT&T  Corporation  dated  October 17, 1995.
                    (Incorporated by reference to Exhibit 10.52 to the Company's
                    Annual  Report  on Form  10-K  filed  for the  period  ended
                    December 31, 1996 (File No. 0-23044))

         10.53*  -  1994  Stock   Option   Plan  for   Non-Employee   Directors.
                    (Incorporated by reference to Exhibit 10.53 to the Company's
                    Annual  Report  on Form  10-K  filed  for the  period  ended
                    December 31, 1996 (File No. 0-23044))

         10.54*  -  Form of Executive  Agreements  (Incorporated by reference to
                    Exhibit  10.54 to the  Company's  Annual Report on Form 10-K
                    filed for the  period  ending  December  31,  1996 (File No.
                    0-23044))

         10.55   -  $150,000,000  Credit  Agreement  dated as of June 28,  1996,
                    among AMSC Subsidiary Corporation, American Mobile Satellite
                    Corporation, the Banks Listed Therein, Morgan Guaranty Trust
                    Company of New York,  as  Documentation  Agent,  and Toronto
                    Dominion   (Texas),    Inc.,   as   Administrative    Agent.
                    (Incorporated by reference to Exhibit 10.55 to the Company's
                    Quarterly  Report on Form 10-Q  filed for the  period  ended
                    June 30, 1996 (File No. 0-23044))


                                     - 36 -

<PAGE>



                    
         10.56   -  $75,000,000  Credit  Agreement  dated as of June  28,  1996,
                    among AMSC Subsidiary Corporation, American Mobile Satellite
                    Corporation, the Banks Listed Therein, Morgan Guaranty Trust
                    Company of New York,  as  Documentation  Agent,  and Toronto
                    Dominion   (Texas),    Inc.,   as   Administrative    Agent.
                    (Incorporated by reference to Exhibit 10.56 to the Company's
                    Quarterly  Report on Form 10-Q  filed for the  period  ended
                    June 30, 1996 (File No. 0-23044))

         10.57   -  Guaranty  Issuance  Agreement  dated as of June 28, 1996, by
                    and  among   Hughes   Electronics   Corporation,   Singapore
                    Telecommunications  Ltd., Baron Capital Partners, L.P., AMSC
                    Subsidiary   Corporation  and  American   Mobile   Satellite
                    Corporation (Incorporated by reference to Exhibit XII to the
                    Amended and Restated  Schedule 13D dated July 1, 1996, filed
                    by Hughes  Communications  Satellite Services,  Inc., Hughes
                    Communications,   Inc.,  Hughes  Aircraft  Company,   Hughes
                    Electronics  Corporation and General Motors Corporation with
                    respect  to shares  of  Common  Stock,  $.01 par  value,  of
                    American Mobile  Satellite  Corporation).  (Incorporated  by
                    reference to Exhibit 10.57 to the Company's Quarterly Report
                    on Form 10-Q filed for the period  ended June 30, 1996 (File
                    No. 0-23044))

         10.57a  -  Amendment No. 1 to Guaranty Issuance Agreement,  dated as of
                    March 27, 1997  (Incorporated by reference to Exhibit 10.57a
                    to the  Company's  Annual  Report on Form 10-K filed for the
                    period ending December 31, 1996 (File No. 0- 23044))

         10.58   -  Guaranty  dated  as  of  June  28,  1996,   made  by  Hughes
                    Electronics  Corporation to Toronto Dominion (Texas),  Inc.,
                    as  Administrative  Agent.  (Incorporated  by  reference  to
                    Exhibit 10.58 to the Company's Quarterly Report on Form 10-Q
                    filed for the period ended June 30, 1996 (File No. 0-23044))

         10.59   -  Warrant No. 1 for the Purchase of 3,750,000  Shares (subject
                    to adjustment) of Common Stock of American Mobile  Satellite
                    Corporation issued to Hughes Electronics Corporation,  dated
                    June 28, 1996  (Incorporated by reference to Exhibit XIII to
                    the Amended and  Restated  Schedule  13D dated July 1, 1996,
                    filed by Hughes  Communications  Satellite  Services,  Inc.,
                    Hughes Communications, Inc., Hughes Aircraft Company, Hughes
                    Electronics  Corporation and General Motors Corporation with
                    respect  to shares  of  Common  Stock,  $.01 par  value,  of
                    American Mobile  Satellite  Corporation).  (Incorporated  by
                    reference to Exhibit 10.57 to the Company's Quarterly Report
                    on Form 10-Q filed for the period  ended June 30, 1996 (File
                    No. 0-23044))

                                     - 37 -

<PAGE>



                    
         10.60  -   Registration  Rights  Agreement  dated as of June 28,  1996,
                    among  American   Mobile   Satellite   Corporation,   Hughes
                    Electronics Corporation,  Singapore Telecommunications Ltd.,
                    and Baron Capital Partners,  L.P. (Incorporated by reference
                    to Exhibit  XIV to the  Amended and  Restated  Schedule  13D
                    dated July 1, 1996, filed by Hughes Communications Satellite
                    Services, Inc., Hughes Communications, Inc., Hughes Aircraft
                    Company,  Hughes Electronics  Corporation and General Motors
                    Corporation with respect to shares of Common Stock, $.01 par
                    value,   of   American   Mobile   Satellite    Corporation).
                    (Incorporated by reference to Exhibit 10.57 to the Company's
                    Quarterly  Report on Form 10-Q  filed for the  period  ended
                    June 30, 1996 (File No. 0-23044))

         10.61  -   Asset Sale  Agreement  dated as of November 22, 1996, by and
                    among  Rockwell  Collins,  Inc.  American  Mobile  Satellite
                    Corporation and AMSC Subsidiary Corporation (Incorporated by
                    reference to Exhibit 10.61 to the Company's  Current  Report
                    on Form 8-K dated  November 22, 1996,  and filed on December
                    9, 1996 (File No. 0-23044))

         10.62  -   Satellite Lease Agreement for the AMSC-1 Satellite, dated as
                    of   December  2,  1997,   By  and  Among  AMSC   Subsidiary
                    Corporation,   American  Mobile  Satellite  Corporation  and
                    African Continental Telecommunications Ltd. (Incorporated by
                    reference to Exhibit 10.61 to the Company's  Current  Report
                    on Form 8-K dated December 4, 1997 (File No. 0-23044))

         10.63  -   Satellite Purchase Agreement,  dated as of December 2, 1997,
                    by  and  Among  TMI  Communications  and  Company,   Limited
                    Partnership  and AMSC  Subsidiary  Corporation  and American
                    Mobile Satellite Corporation.  (Incorporated by reference to
                    Exhibit  10.61 to the Company's  Current  Report on Form 8-K
                    dated December 4, 1997 (File No. 0-23044))

         10.64  -   Bridge Loan  Agreement,  dated as of December 30, 1997, made
                    by and among AMSC  Subsidiary  Corporation,  American Mobile
                    Satellite  Corporation and Hughes  Communications  Satellite
                    Services, Inc. (filed herewith)

         10.64a -   Pledge  Agreement  dated as of December  30,  1997,  made by
                    American    Mobile    Satellite    Corporation   to   Hughes
                    Communications Satellite Services, Inc. (filed herewith)

         10.64b -   Term Note for  $10,000,000  dated  December  30, 1997 (filed
                    herewith)


                                     - 38 -

<PAGE>



         10.65   -  Stock  Purchase  Agreement for the  Acquisition  of Motorola
                    ARDIS  Acquisition,  Inc. and Motorola  ARDIS,  Inc. by AMSC
                    Acquisition  Company,  Inc., a Wholly-  Owned  Subsidiary of
                    American Mobile Satellite Corporation,  Dated as of December
                    31, 1997 (filed herewith)

         10.66   -  Participation Rights Agreement by and among Motorola,  Inc.,
                    American  Mobile  Satellite  Corporation,  and  the  parties
                    listed on Schedule  A, dated as of December  31, 1997 (filed
                    herewith)

         11.1    -  Computation of Net Loss Per Share (filed herewith)

         21.1    -  Subsidiaries of American Mobile (filed herewith)

         23.1    -  Consent of Arthur Andersen LLP (filed herewith)

         27.1    -  Financial Data Schedule (filed herewith)

- ------------------------------------

*Management contract or compensatory plan or arrangement required to be filed as
an exhibit to this report pursuant to Item 14(c) of this report.



                                     - 39 -

<PAGE>



(b)      Reports on Form 8-K:

          On December 8, 1997,  the Company filed a Current  Report on Form 8-K,
          describing in response to Item 5-Other  Events,  regarding the Company
          entering  into two  simultaneous  transactions:  (i)  Satellite  Lease
          Agreement  for the  AMSC-1  Satellite,  By and Among  AMSC  Subsidiary
          Corporation,   American  Mobile  Satellite   Corporation  and  African
          Continental  Telecommunications and (ii) Satellite Purchase Agreement,
          By and Among TMI Communications and Company,  Limited  Partnership and
          AMSC Subsidiary Corporation and American Mobile Satellite Corporation.

          On January 5, 1998,  the Company  filed a Current  Report on Form 8-K,
          describing in response to Item 5-Other Events,  in the form of a press
          release,  regarding  the Company  entering  into two  agreements:  (i)
          Bridge Loan Agreement with Hughes  Communications  Satellite Services,
          Inc. and (ii) Stock Purchase  Agreement  with  Motorola,  Inc. for the
          acquisition of ARDIS Company.

          On January 13,  1998,  the Company  filed an  Amendment to its Current
          Report on Form 8-K/A  amending and restating  under Item 7 - Financial
          Statements, Pro Forma Financial Information and Exhibits the financial
          statements  to  American  Mobile's  acquisition  previously  filed  on
          February 6, 1997.  On January 22,  1998,  the Company  filed a Current
          Report on Form 8-K, describing in response to Item 5-Other Events, the
          resignation  of director  David A. Juliano and the election of Douglas
          I. Brandon to fill the vacancy created by Mr. Juliano's resignation.

          On March 9,  1998,  the  Company  filed a Current  Report on Form 8-K,
          describing  in  response  to Item  5-Other  Events,  an  excerpt  of a
          financing  document of American Mobile  Satellite  Corporation and its
          subsidiary, AMSC Acquisition Company, Inc.


                                     - 40 -

<PAGE>



SIGNATURES

Pursuant to the  requirements of Section 13 or 15(d) of the Securities  Exchange
Act of 1934,  the  registrant  has duly  caused  this report to be signed on its
behalf by the undersigned, thereunto duly authorized.

                                           AMERICAN MOBILE SATELLITE CORPORATION


                                            By       /s/ Gary M. Parsons

                                                     Gary M. Parsons
                                                     Chief Executive Officer and
                                                        Chairman of the Board

Date:   March 31, 1998

Pursuant to the requirements of the Securities Exchange Act of 1934, this report
has been signed below by the following  persons on behalf of the  registrant and
in the capacities and on the dates indicated.

/s/Gary M. Parsons              Chief Executive Officer           March 31, 1998
Gary M. Parsons                 Chairman of the Board
                                (principal executive officer)

/s/Stephen D. Peck              Vice President and Chief          March 31, 1998
Stephen D. Peck                 Financial Officer
                                (principal financial and 
                                 accounting officer)


/s/Douglas I. Brandon           Director                          March 31, 1998
Douglas I. Brandon


/s/Steven D. Dorfman            Director                          March 31, 1998
Steven D. Dorfman


/s/Ho Siaw Hong                 Director                          March 31, 1998
Ho Siaw Hong


______________________          Director                          March 31, 1998
Billy J. Parrott




                                     - 41 -

<PAGE>







/s/Andrew A. Quartner           Director                          March 31, 1998
Andrew A. Quartner


/s/Jack A. Shaw                 Director                          March 31, 1998
Jack A. Shaw


/s/Roderick M. Sherwood, III    Director                          March 31, 1998
Roderick M. Sherwood, III


_______________________         Director                          March 31, 1998
Michael T. Smith


/s/Yap Chee Keong               Director                          March 31, 1998
Yap Chee Keong


/s/Albert L. Zesiger            Director                          March 31, 1998
Albert L. Zesiger


                                  





                                      -42-


<PAGE>





                                      INDEX



Management's Discussion and Analysis of Financial Condition
          and Results of Operations.......................................F - 1

Report of Independent Public Accountants..................................F - 15

Consolidated Statements of Loss...........................................F - 16

Consolidated Balance Sheets...............................................F - 17

Consolidated Statements of Stockholders' Equity...........................F - 18

Consolidated Statements of Cash Flows.....................................F - 19

Notes to Consolidated Financial Statements................................F - 20

Quarterly Financial Data..................................................F - 49

Selected Financial Data...................................................F - 50

















                                       F-i

<PAGE>



          Management's Discussion and Analysis of Financial Condition
                           and Results of Operations

This Annual Report on Form 10-K includes "forward-looking statements" within the
meaning of Section  27A of the  Securities  Act of 1933 and  Section  21E of the
Securities  Exchange Act of 1934.  Such  statements are identified by the use of
forward-looking  words or phrases  including,  but not limited  to,  "believes,"
"intended,"   "will  be   positioned,"   "expects,"   "expected,"   "estimates,"
"anticipates" and "anticipated." These  forward-looking  statements are based on
the Company's  current  expectations.  All statements  other than  statements of
historical  facts included in this Annual Report,  including those regarding the
Company's financial position,  business strategy,  projected costs and financing
needs,  and plans and  objectives  of  management  for  future  operations,  are
forward-looking statements.  Although the Company believes that the expectations
reflected in such  forward-looking  statements are  reasonable,  there can be no
assurance  that  such  expectations  will  prove to have been  correct.  Because
forward-looking statements involve risks and uncertainties, the Company's actual
results  could  differ  materially.  Important  factors  that could cause actual
results  to  differ  materially  from the  Company's  expectations  ("Cautionary
Statements")  are disclosed under  "Business" and  "Management's  Discussion and
Analysis of Financial  Condition  and Results of  Operations,"  and elsewhere in
this Annual Report,  including,  without  limitation,  in  conjunction  with the
forward-looking statements included in this Annual Report. These forward-looking
statements  represent the  Company's  judgment as of the date hereof and readers
are cautioned not to place undue reliance on these  forward-looking  statements.
All subsequent written and oral forward-looking  statements  attributable to the
Company or persons  acting on behalf of the Company are  expressly  qualified in
their entirety by the Cautionary Statements. Readers should carefully review the
risk factors  described in other  documents  the Company files from time to time
with the  Securities  and Exchange  Commission,  including the Current Report on
Form 8-K filed on March 9, 1998, and Form 10-Q Quarterly  Reports to be filed by
the Company  subsequent to this Form 10-K Annual Report and any Current  Reports
on Form 8-K and registration statements filed by the Company.


General

The following  discussion and analysis  provides  information  which  management
believes  is  relevant  to an  assessment  and  understanding  of the  financial
condition and  consolidated  results of operations of American Mobile  Satellite
Corporation  (with its subsidiaries,  "American  Mobile" or the "Company").  The
discussion  should  be read  in  conjunction  with  the  consolidated  financial
statements and notes thereto.

American Mobile  Satellite  Corporation was  incorporated in May 1988 and, until
1996,  was a  development  stage  company,  engaged  primarily  in  the  design,
development,  construction,  deployment  and  financing  of a  mobile  satellite
communication  system.  On December 31, 1997,  the Company  entered into a Stock
Purchase Agreement (the "Purchase Agreement") with Motorola,  Inc. ("Motorola"),
for  the  acquisition  (the   "Acquisition")  of  ARDIS  Company  ("ARDIS"),   a
wholly-owned  subsidiary of Motorola  that owns and operates a two-way  wireless
data  communications  network.  On March 3,  1998,  the FCC  granted  consent to
consummate  the  Acquisition.  On March 31, 1998,  the  Acquisition  and related


                                       F-1

<PAGE>


financing  were  completed.  See  "Liquidity  and Capital  Resources."  With the
acquisition  of ARDIS,  the Company  becomes a leading  provider  of  nationwide
wireless communications  services,  including data, dispatch and voice services,
primarily to business  customers in the United States.  The Company will offer a
broad  range of  end-to-end  wireless  solutions  utilizing  a seamless  network
consisting of the nation's largest,  most  fully-deployed  terrestrial  wireless
data network (the "ARDIS Network") and a satellite in geosynchronous  orbit (the
"Satellite Network")(together, the "Network").

In connection with the  Acquisition,  the Company and its  subsidiaries  entered
into agreements with respect to the following  financings and refinancings:  (1)
$335  million of Units;  (2) the  restructuring  of its  existing  $200  million
Revolving  Credit Facility and Term Loan Facility  (collectively,  the "New Bank
Financings");  and (3) $10 million  commitment  with respect to Motorola  vendor
financing.  See "Management's Discussion and Analysis of Financial Condition and
Results of Operations - Liquidity and Capital Resources."

On October 16, 1997,  American Mobile Radio Corporation,  an indirect subsidiary
of American  Mobile through its subsidiary  AMRC Holdings,  Inc.  (together with
American Mobile Radio Corporation,  "AMRC"), was awarded a license by the FCC to
provide  satellite-based  Digital Audio Radio Service  ("DARS")  throughout  the
United States, following its successful $89.9 million bid at auction on April 2,
1997.  American  Mobile has entered  into an  agreement  with  WorldSpace,  Inc.
("WorldSpace"), by which WorldSpace has acquired a 20% participation in AMRC. In
connection  with the DARS  auction,  AMRC has also arranged for financing of the
FCC license fees as well as for initial working  capital needs,  which financing
has included the issuance of options.  Under the terms of AMRC's  financing  and
contingent on FCC approval,  exercise of the  outstanding  issued  options could
result in the dilution of American Mobile's  ownership  interest in AMRC to 28%.
Additionally,  the agreement gives WorldSpace certain participation rights which
provide  for  their  participation  in  significant  business  decisions  in the
ordinary course of business.  As a result, AMRC is carried on the equity method.
The operations and financing of AMRC are maintained  separate and apart from the
operations and financing of American Mobile (see "Liquidity and Financing").

On  December  4, 1997,  the  Company  entered  into an  agreement  with  African
Continental  Telecommunications Ltd. ("ACTEL") to lease the Company's satellite,
"MSAT-2" (the  "Satellite  Lease  Agreement")  for deployment  over  sub-Saharan
Africa.  Simultaneously,  the Company agreed with TMI Communications and Company
Limited  Partnership  ("TMI") to acquire a one-half  ownership interest in TMI's
satellite,  "MSAT-1" (the "Satellite Purchase Agreement"). See Item I. "Business
- -- Satellite Lease and Purchase Agreement", "-Satellite Back-up and Technology,"
and Management's  Discussion and Analysis of Financial  Condition and Results of
Operations - Liquidity and Capital Resources."

In  late 1996 the  Company   expanded  its  mobile  data  business  through  the
acquisition  of  Rockwell  International  Corporation's  ("Rockwell")  dual mode
mobile  messaging and global  positioning and monitoring  service for commercial
trucking fleets  ("MCSS").  In the transaction,  the Company assumed  Rockwell's
existing customer contracts,  and acquired Rockwell's system  infrastructure for


                                       F-2

<PAGE>


delivering  their  mobile  data  product,  as well as  Rockwell's  rights to the
multi-mode,  satellite-terrestrial  product.  The  assets of the  business  were
acquired  through the  assumption of the various  contracts and  obligations  of
Rockwell relating to the business;  no additional payments were made to Rockwell
under the terms of the Asset Sale  Agreement  dated as of November 22, 1996. See
"Liquidity and Capital Resources."

Management  believes the period to period comparison of the Company's  financial
results  are not  necessarily  meaningful  and should  not be relied  upon as an
indication of future  operating  performance  due to the Company's  historically
high growth rate and the acquisition of MCSS and ARDIS.


Overview

Each of American Mobile and ARDIS has incurred significant  operating losses and
negative cash flows in each year since it commenced operations, due primarily to
start-up  costs,  the costs of developing and building each network and the cost
of developing,  selling and providing its respective products and services.  The
Company is, and will continue to be, highly leveraged.  As of December 31, 1997,
on a pro forma basis,  the Company would have had  indebtedness of approximately
$454.9 million,  assuming the  Acquisition,  the issuance of the $335 million of
Units, and restructuring of the bank financing (see "Recent Financing Activity")
occurred on December 31, 1997.

The Company's future operating  results could be adversely  affected by a number
of uncertainties and factors, including (i) the timely completion and deployment
of  future  products  and  related  services,   including  among  other  things,
availability of mobile telephones, data terminals and other equipment to be used
with the Network  ("Subscriber  Equipment") being  manufactured by third parties
over which the Company has limited control,  (ii) the market's acceptance of the
Company's  services,  (iii) the  ability  and the  commitment  of the  Company's
distribution channels to market and distribute the Company's services,  (iv) the
Company's  ability to modify  its  organization,  strategy  and  product  mix to
maximize the market  opportunities in light of changes therein,  (v) competition
from existing  companies that provide  services  using  existing  communications
technologies  and the  possibility  of  competition  from  companies  using  new
technology  in  the  future,   (vi)  capacity   constraints   arising  from  the
reconfiguration of MSAT-2,  subsequent anomalies affecting MSAT-2 and MSAT-1, or
the power management  recommendation affecting both MSAT-2 and MSAT-1 previously
reported,  (vii)  additional  technical  anomalies  that may  occur  within  the
Satellite  Network,  including those relating to MSAT-1 and MSAT-2,  which could
impact, among other things, the operation of the Satellite Network and the cost,
scope  or  availability  of  in-orbit  insurance,  (viii)  subscriber  equipment
inventory  responsibilities and liabilities assumed by the Company including the
ability of the Company to realize the value of its inventory in a timely manner,
(ix) the Company's ability to secure  additional  financing as may be necessary,
(x) the  Company's  ability to respond and react to changes in its  business and
the  industry  as a result of being  highly  leveraged,  (xi) the ability of the
Company  to  successfully  integrate  ARDIS  and  to  achieve  certain  business
synergies, and (xii) the ability of the Company to manage growth effectively.


                                       F-3

<PAGE>



The  Company's  operating  results  and capital  and  liquidity  needs have been
materially  affected by delays experienced in the acquisition of subscribers and
the related  equipment  sales. As a result,  the Company shifted from a consumer
focus to a business  to business  focus in late 1996.  Such shift has caused the
Company to refocus certain  business  resources and to re-organize the sales and
marketing organization. The impact of this delay has substantially decreased the
Company's anticipated revenues and increased the Company's capital and liquidity
needs.  No  assurance  can be  given  that  additional  delays  relating  to the
acquisition of subscribers  and delayed  equipment sales will not be encountered
in the future and not have an adverse impact on the Company.

As of December 31, 1997, there were approximately  32,400 units on the Satellite
Network.


Years Ended December 31, 1997 and 1996

Service  revenues,  which  include both the Company's  voice and data  services,
approximated  $20.7  million for 1997 as  compared to $9.2  million for 1996 and
represents a 125% increase year over year.  Service  revenue from voice services
increased 100% from  approximately  $5.0 million in 1996 to approximately  $10.0
million in 1997.  The $5.0  million  increase  was  primarily a result of a 101%
increase in voice customers during 1997. Service revenue from the Company's data
services  approximated  $7.6  million in 1997,  as compared to $2.3  million for
1996,  an increase of $5.4 million or 245%.  The increase was primarily a result
of  additional  revenue  from  dual  mode  subscribers  added as a result of the
acquisition,  on November  1996,  of Rockwell's  dual mode mobile  messaging and
global positioning and monitoring  service,  as compared to the revenue received
in 1996 for satellite capacity leased by Rockwell. Service revenue from capacity
resellers, who handle both voice and data services, approximated $2.8 million in
1997,  as compared to $1.8 million in 1996,  an increase of $1.0 million or 56%.
As of December 31, 1997 and 1996,  receivables relating to service revenues were
$3.6 million and $1.8 million, respectively.

Revenue from the sale of mobile data terminals and mobile  telephones  increased
27% from  $18.5  million  in 1996 to $23.5  million  in 1997.  The  increase was
primarily  attributable  to increased  equipment  sales of the dual-mode  mobile
messaging  product,   discussed  above.  As  of  December  31,  1997  and  1996,
receivables  relating to  equipment  revenue  were $5.9 million and $5.8 million
respectively.

Cost of  service  and  operations  for 1997,  which  includes  costs to  support
subscribers  and to operate the Satellite  Network,  were $32.0 million for 1997
and $30.5 million for 1996. Cost of service and operations for 1997 and 1996, as
a percentage of revenues, were 72% and 110%, respectively.  The increase in cost
of  service  and  operations  was  primarily   attributable   to  (i)  increased
interconnect  charges associated with increased service usage by customers,  and
(ii) the  additional  cost  associated  with  supporting  the dual  mode  mobile
messaging  product  discussed  above,  offset  by  a  reduction  in  information
technology  costs  affected by  dramatically  reducing the dependence on outside
consultants.


                                       F-4

<PAGE>



The cost of equipment  sold  increased  26% from $31.9  million in 1996 to $40.3
million in 1997. The dollar  increase in the cost of equipment sold is primarily
attributable  to (i) increased  sales as a result of the acquisition of the dual
mode messaging product, (ii) an increase of $600,000 in inventory carrying costs
as certain  subscriber  equipment  contracts were  fulfilled,  and (iii) a $12.0
million write down of inventory to net  realizable  value in 1997 as compared to
$11.1 million write down and reconfiguration charges in 1996.

Sales and  advertising  expenses were $12.1  million in 1997,  compared to $24.5
million in 1996. Sales and advertising  expenses as a percentage of revenue were
27% in 1997 and 88% in 1996. The decrease of sales and advertising expenses  was
primarily  attributable  to (i) a more focused  approach to  advertising  as the
company has moved from consumer markets to targeted  business-to-business sales,
and the resulting  reduction in print  advertising,  (ii) increased costs in the
first  quarter of 1996 for the  development  of  collateral  material  needed to
support the sales effort,  and (iii) costs incurred in the first quarter of 1996
associated with the formal launch of service.

General and  administrative  expenses for 1997 were $14.8  million,  compared to
$17.5 million in 1996. As a percentage  of revenue,  general and  administrative
expenses  represented  34% in 1997 and 63% in 1996.  The decrease in general and
administrative  expenses for 1997 compared to 1996 was primarily attributable to
reductions  made in staffing as a result of a  management  restructuring  in the
third quarter of 1996 and the associated severance costs.

Depreciation  and  amortization  expense was $42.4  million and $43.4 million in
1997 and 1996, respectively,  representing approximately 96% and 156% of revenue
for 1997 and 1996,  respectively.  The overall dollar and percentage decrease in
depreciation and  amortization  expense was attributable to the reduction of the
carrying value of the satellite as a result of the  resolution,  in August 1996,
of claims under the Company's satellite insurance contracts and policies and the
receipt  of  approximately  $66.0  million,  offset by a $1.0  million  one-time
charge, in the second quarter of 1997, associated with increased amortization in
accordance with SFAS No.86 of certain cost associated with software  development
for the mobile data product.

Interest  income was $247,000 in 1997 compared to $552,000 in 1996. The decrease
was a result of lower average cash balances.  The Company incurred $21.6 million
of interest  expense in 1997  compared to $15.2  million of interest  expense in
1996 reflecting (i) the amortization of debt discount and debt offering costs in
the amount of $9.4 million in 1997,  compared to $5.7 million in 1996,  and (ii)
higher  outstanding loan balances as compared to 1996.  During 1997, the Company
received other income in the amount of $875,000  representing  proceeds from the
licensing of certain technology associated with the Satellite Network.

Interest  expense in 1997 was  significant  as a result of borrowings  under the
Bank  Financing,  as well as the  amortization  of borrowing  costs  incurred in


                                       F-5

<PAGE>


conjunction  with securing the facility.  It is anticipated  that interest costs
will  continue  to be  significant  as a result  of the Bank  Financing,  Bridge
Financing, and Acquisition, (see "Liquidity and Capital Resources").

Net capital expenditures,  including additions financed through vendor financing
arrangements,  for 1997 for property and equipment were $8.8 million compared to
capital  reductions  of $51.0 million in 1996.  The $59.4  million  increase was
largely  attributable  to (i) the net proceeds in 1996 of $66.0 million from the
resolution of the claims under the Company's  satellite  insurance contracts and
policies (see "Liquidity and Capital  Resources") and (ii) the decrease in asset
acquisitions  associated with the final build-out of the  communications  ground
segment (the "CGS").


Years Ended December 31, 1996 and 1995

Service  revenues,  which  include both the Company's  voice and data  services,
approximated  $9.2  million for 1996 as compared to $6.9  million for 1995 which
represents a 33% increase year over year.  Service  revenue from voice  services
approximated  $5.0  million  in  1996,  including   approximately  $1.3  million
attributable to satellite  capacity leased to TMI, under a commitment  which was
completed  in May 1996.  Service  revenue from the  Company's  data and position
location  services  ("Mobile  Data  Communication  Service")  approximated  $2.2
million in 1996,  as compared to $1.7 for 1995,  an increase of $500,000 or 29%.
Service revenue from capacity resellers who handle both voice and data services,
approximated  $1.8  million in 1996,  as  compared  to $5.2  million in 1995,  a
decrease of $3.4 million or 65%. Prior to 1996, the Company  provided its Mobile
Data   Communication   Service  using   satellite   capacity   leased  from  the
Communications  Satellite Corporation  ("COMSAT"),  the cost of which was passed
through to one  customer  (Rockwell).  The  decrease  in revenue  from  capacity
resellers  reflects  the reduced  revenue  from  Rockwell  resulting  from lower
billings for the use of the lower cost MSAT-2 versus  billings  attributable  to
the leased  COMSAT  satellite  applied on a  pass-through  basis.  As previously
discussed,  the  Company  acquired  the dual mode  mobile  messaging  and global
positioning and monitoring service of Rockwell in November 1996. At December 31,
1996 and 1995,  receivables relating to service revenues were $1.8 and $405,000,
respectively.

Revenue from the sale of mobile data terminals and mobile  telephones  increased
from $1.9 million in 1995 to $18.5 million in 1996,  primarily  attributable  to
(i) the Company's  introduction  of certain voice products in the fourth quarter
of 1995 and the  resulting  sale of mobile  telephones,  and (ii) the  increased
availability  of mobile data  terminals  in 1996  compared  to 1995  following a
contract signed with a mobile data terminal manufacturer in February 1995.

The Company's costs and expenses have primarily increased in connection with the
start  of  full  commercial  service  in  December  1995.  Cost of  service  and
operations for 1996, which includes costs to support  subscribers and to operate
the Satellite Network,  were $30.5 million for 1996, an increase of $6.5 million
from 1995.  Cost of service and operations for 1996 and 1995, as a percentage of
revenue were 110% and 272%, respectively. The dollar increase in cost of service


                                       F-6

<PAGE>


and  operations  was  primarily  attributable  to (i)  additional  personnel and
related costs to support both existing and  anticipated  customer  demand,  (ii)
increased  costs  associated  with the  on-going  maintenance  of the  Company's
billing  systems and the CGS, and (iii) $6.5  million of  insurance  expense for
in-orbit  insurance  coverage for MSAT-2,  offset by the  elimination  of COMSAT
lease expense  reflecting  the  transition of the Company's  customers  from the
leased satellite to MSAT-2.

The cost of equipment  sold increased to $31.9 million in 1996 from $4.7 million
in 1995. The increase in cost of equipment sold is primarily attributable to (i)
the Company's  introduction  of certain voice  products in the fourth quarter of
1995 and the  resulting  sale of mobile  telephones,  (ii) the  availability  of
mobile data  terminals in 1996 compared to 1995,  (iii) a $4.2 million charge in
1996 for the  reconfiguration  of certain  components  to better  meet  customer
requirements,  and (iv) a $6.9 million write down of inventory to net realizable
value in 1996.

Sales and  advertising  expenses were $24.5  million in 1996,  compared to $22.8
million in 1995. Sales and advertising  expenses as a percentage of revenue were
88% in 1996 and 259% in 1995. The increase of sales and advertising expenses was
primarily  attributable to (i) additional head count and personnel related costs
associated  with the increase in sales staff,  and (ii) increased costs directly
associated  with the increase in subscriber  acquisition  programs,  offset by a
$1.4 million charge,  in 1995,  associated with the  reacquisition  of defective
equipment located at a customer site and settlement of related disputes.

General and administrative  expenses for 1996 were $17.5 million, an increase of
$0.8  million as  compared to 1995.  As a  percentage  of  revenue,  general and
administrative  expenses  represented  63% in 1996 and 190% in 1995.  The dollar
increase in general and  administrative  expenses for 1996  compared to 1995 was
primarily   attributable  to  (i)  approximately  $675,000  of  severance  costs
associated  with a management  restructuring  and (ii) an increase in facilities
rents and  utilities  of $236,000.  The  decrease of general and  administrative
expenses as a percentage of operating  expenses was  attributable to the overall
increase in operating expenses.

Depreciation  and  amortization  expense was $43.4  million and $11.2 million in
1996 and 1995, respectively, representing approximately 156% and 128% of revenue
for 1996 and 1995,  respectively.  The increase in depreciation and amortization
expense was  attributable to the commencement of depreciation of both MSAT-2 and
related assets and the CGS in the fourth quarter of 1995.

Interest and other income was $552,000 in 1996 compared to $4.5 million in 1995.
The decrease was a result of lower average cash balances.  The Company  incurred
$15.2  million of  interest  expense in 1996  compared  to  $916,000 of interest
expense  in  1995   reflecting   (i)  the   discontinuation   of  interest  cost
capitalization as a result of substantially  completing the Satellite Network in
the fourth  quarter of 1995,  (ii) the  amortization  of debt  discount and debt
offering  costs  (including  Guarantee  Warrants  (see  "Liquidity  and  Capital
Resources")) relating to the Bridge Financing and Bank Financing (see "Liquidity
and Capital Resources"),  and (iii) higher outstanding loan balances as compared
to 1995.


                                       F-7

<PAGE>



Net capital  reductions,  including  additions financed through vendor financing
arrangements, for 1996 for property and equipment were $51.0 million compared to
capital  expenditures  of  $86.7  million  in 1995.  The  decrease  was  largely
attributable to (i) the net proceeds of $66.0 million from the resolution of the
claims under the  Company's  satellite  insurance  contracts  and policies  (see
"Liquidity and Capital Resources"),  (ii) the purchase,  in the first quarter of
1995,  of  launch  insurance  at a cost  to the  Company  of  $42.8  million  in
connection with the Company's  launch  contract with Martin Marietta  Commercial
Launch  Services,  Inc.,  and (iii) the  decrease  in  construction  activity as
certain components of the CGS were completed.


Liquidity and Capital Resources

Adequate  liquidity  and capital  are  critical to the ability of the Company to
continue  as a  going  concern  and  to  fund  subscriber  acquisition  programs
necessary  to reach cash  positive  and  profitable  operations.  To satisfy its
ongoing  financing  needs,  the Company,  on June 28, 1996,  established  a $219
million debt facility (the "Bank Financing"), of which $200 million is available
and fully guaranteed by certain American Mobile shareholders (the "Guarantors").
As of December 31, 1997,  the Bank  Financing  consisted  of: (i) a $144 million
five-year,  multi-draw  term loan  facility  (the  "Term  Loan  Facility")  with
quarterly  payments  commencing  March 31, 1999 through and  including  June 30,
2001, and (ii) a $56 million  five-year  revolving credit facility with a bullet
maturity on June 30, 2001 (the "Working  Capital  Facility").  Proceeds from the
Bank  Financing  were  used to repay  the  Company's  interim  financing  and to
refinance short-term vendor financing, and for general working capital purposes.
As previously  reported,  the Company,  on March 27, 1997,  reached an agreement
with the  Guarantors to eliminate all covenant  tests in exchange for additional
warrants and a repricing of warrants previously issued (together, the "Guarantee
Warrants").  As a result of the repricing,  the Guarantee Warrants were revalued
at $21.9  million.  As of March 20,  1998,  the  Company  had drawn down  $144.0
million of the Term Loan Facility at annual  interest  rates ranging from 6.025%
to 6.0875% and $56.0 million of the Working Capital  Facility at annual interest
rates ranging from 6.025% to 6.2125%.

As previously  mentioned (see  "Organization and Business"),  AMRC was a winning
bidder for, and on October 16, 1997,  was awarded an FCC license to provide DARS
throughout the United States.  AMRC has and will continue to receive funding for
this  business  from an  independent  source in exchange  for debt and an equity
interest in AMRC.  Accordingly,  it is not expected that the development of this
business  will have a  material  impact  on the  Company's  financial  position,
results of operations, or cash flows. The Company's equity interest in AMRC may,
however, even on a fully diluted basis, become a material asset of the Company.

In the last quarter of 1997, the Company arranged the financing of certain trade
payables,  and as of December 31, 1997, $11.7 million of deferred trade payables
were outstanding at rates ranging from 6.23% to 14% and are generally payable by
the end of 1998.


                                       F-8

<PAGE>



On December 4, 1997, the Company entered into two simultaneous transactions. The
Company  agreed  with TMI to  acquire a  one-half  ownership  interest  in TMI's
satellite, MSAT-1, at a cost of $60 million payable in equal installments over a
five-year  period  (the  "Satellite  Purchase  Agreement");  certain  additional
payments  to TMI are  contemplated  in the event that  additional  benefits  are
realized  by the  Company.  Under  the  Satellite  Purchase  Agreement,  TMI and
American  Mobile will each own a 50% undivided ownership  interest in the Shared
Satellite,  will  jointly  be  responsible  for  the  operation  of  the  Shared
Satellite, and  will  share  certain  satellite  operating  expenses,  but  will
otherwise maintain their separate business operations.

Simultaneously,  the Company  entered into an agreement  (the  "Satellite  Lease
Agreement") with African Continental  Telecommunications Ltd. ("ACTEL"), for the
lease of MSAT-2,  for deployment over  sub-Saharan  Africa.  The five-year lease
provides for  aggregate  lease  payments to the Company of $182.5  million.  The
lease includes a renewal  option  through the end of the life of MSAT-2,  on the
same lease terms, at ACTEL's  election  exercisable 2 1/2 years prior to the end
of the initial lease term.

Closing under the Satellite  Purchase Agreement and Satellite Lease Agreement is
subject  to a number  of  conditions,  including:  United  States  and  Canadian
regulatory approvals,  a successful financing by ACTEL of at least $120 million,
completion of certain  satellite  testing,  inversion and relocation  activities
with  respect to MSAT-2,  to support  the  contemplated  services  over  Africa;
receipt of various government  authorizations  from Gibraltar,  South Africa and
other jurisdictions to support satellite  relocation,  including  authorizations
with  respect to orbital  slot and  spectrum  coordination;  and  completion  of
certain  system   development   activities   sufficient  to  support   satellite
redeployment.  On March 13, 1998, the FCC provided approval of the transactions;
Canadian  government  coordination  and  approvals  remain  outstanding.  It  is
anticipated  that the closing under both the purchase and lease  agreements will
occur simultaneously in the spring of 1998.

On December 31, 1997,  the Company  entered  into a Bridge Loan  Agreement  (the
"Bridge Loan") with Hughes Communications Satellite Services, Inc. ("Hughes") in
the principal amount of up to $10 million,  secured by a pledge of the Company's
interest in its 80%-owned subsidiary,  AMRC Holdings,  Inc. The Bridge Loan bore
an annual  interest  rate of 12%,  had a maturity  date of March 31,  1999,  and
required  mandatory  repayment in the event net  proceeds are received  from any
asset  disposition,  lease  agreement,  financing or equity  transaction  of the
Company.  The Bridge Loan was drawn down in full,  and repaid on March 31, 1998,
with a portion of the proceeds of the Notes (described below).


Recent Financing Activity

$335 Million Unit Offering

In connection  with the  Acquisition,  the Company  issued $335 million of Units
(the  "Units")  consisting of 12 1/4% Senior Notes due 2008 (the  "Notes"),  and


                                       F-9

<PAGE>


Warrants to purchase  shares of Common Stock of the Company.  Each Unit consists
of $1,000  principal  amount of Notes and one Warrant to purchase 3.75749 shares
of Common Stock at an exercise  price of $12.51 per share.  A portion of the net
proceeds  of the sale of the Units were used to  finance  the  Acquisition.  The
Notes are fully guaranteed by American Mobile Satellite Corporation.


New Bank Financing

In connection with the Acquisition, the Company, the Acquisition Company and its
subsidiaries  restructured  the existing $200 million Bank  Financing (the "Bank
Financing") to provide for two facilities:  (i) the Revolving Credit Facility, a
$100 million unsecured  five-year reducing  revolving credit facility,  and (ii)
the Term Loan Facility, a $100 million five-year,  term loan facility with up to
three  additional  one-year  extensions  subject to the lenders'  approval.  The
Revolving  Credit  Facility  will rank pari passu with the Notes.  The Term Loan
Facility is secured by the assets of the Company,  principally its stockholdings
in AMRC and the Acquisition Company, and will be effectively subordinated to the
Revolving  Credit  Facility and the Notes.  The New Bank  Financing is severally
guaranteed   by   Hughes   Electronics   Corporation    ("Hughes"),    Singapore
Telecommunications  Ltd. ("Singapore Telecom") and Baron Capital Partners,  L.P.
(the "Bank Facility  Guarantors").  The lenders'  placement fee for the New Bank
Financing is approximately $500,000.


The Revolving Credit Facility

The Revolving  Credit  Facility bears an interest rate,  generally,  of 50 basis
points above London  Interbank  Offered Rate ("LIBOR") and is unsecured,  with a
negative  pledge on the assets of the Acquisition  Company and its  subsidiaries
ranking pari passu with the Notes. The Revolving Credit Facility will be reduced
$10 million each quarter,  beginning with the quarter ending June 30, 2002, with
the balance due on maturity of March 31, 2003.  Certain proceeds received by the
Acquisition  Company would be required to repay and reduce the Revolving  Credit
Facility,  unless  otherwise  waived  by  the  lenders  and  the  Bank  Facility
Guarantors:  (1) 100% of excess cash flow obtained by the  Acquisition  Company;
(2) the first $25.0 million net proceeds of the lease or sale of MSAT-2 received
by the  Acquisition  Company,  and  thereafter  75% of  the  remaining  proceeds
received  from such  lease or sale (the  remaining  25% may be  retained  by the
Acquisition  Company for business  operations);  (3) 100% of the proceeds of any
other asset sales by the Acquisition Company; (4) 50% of the net proceeds of any
offerings of the Acquisition  Company's equity (the remaining 50% to be retained
by the Acquisition Company for business  operations);  and (5) 100% of any major
casualty  proceeds.  At such time as the Revolving  Credit Facility is repaid in
full, and subject to satisfaction of the restrictive  payments provisions of the
Notes, any prepayment  amounts that would otherwise have been used to prepay the
Revolving Credit Facility will be dividended to the Company.


                                      F-10

<PAGE>



The Term Loan Facility

The Term Loan Facility  bears an interest  rate,  generally,  of 50 basis points
above  LIBOR and is  secured  by the  assets  of the  Company,  principally  its
stockholdings in AMRC and the Acquisition  Company. The Term Loan Agreement does
not include any scheduled  amortization until maturity, but does contain certain
provisions for  prepayment  based on certain  proceeds  received by the Company,
unless otherwise waived by the Banks and the Bank Facility Guarantors:  (1) 100%
of excess cash flow  obtained by the  Company;  (2) the first $25.0  million net
proceeds of the lease or sale of MSAT-2 received by the Company,  and thereafter
75% of the remaining  proceeds  received from such lease or sale (the  remaining
25% to be retained by the Acquisition Company for business operations); (3) 100%
of the  proceeds  of any other asset  sales by the  Company;  (4) 50% of the net
proceeds  of any  equity  offerings  of the  Company  (the  remaining  50% to be
retained  by the  Company for  business  operations);  and (5) 100% of any major
casualty  proceeds of the Company.  To the extent that the Term Loan Facility is
repaid, the aforementioned proceeds that would otherwise have been used to repay
the Term Loan Facility will be used to repay and reduce the commitment under the
Revolving Credit Facility.


The Guarantees

In connection  with the New Bank  Financing,  the Bank Facility  Guarantors have
agreed  to  extend  separate  guarantees  of  the  obligations  of  each  of the
Acquisition  Company  and the  Company  to the Banks,  which on a several  basis
aggregate  to $200  million.  In their  agreement  with each of the  Acquisition
Company and the Company (the "Guarantee Issuance Agreement"),  the Bank Facility
Guarantors  have  agreed to make  their  guarantees  available  for the New Bank
Financing.  The Guarantee  Issuance  Agreement will include  certain  additional
agreements of the Acquisition  Company and of the Company including with respect
to financial  performance of the  Acquisition  Company  relating to the ratio of
debt to EBITDA and service  revenue,  which,  if not met,  could, if not waived,
limit the Acquisition Company's ability to draw down on additional amounts under
the  Revolving  Credit  Facility  and  result  in a  default  under the New Bank
Financing  beginning in 1999. In exchange for the additional risks undertaken by
the Bank  Facility  Guarantors in connection  with the New Bank  Financing,  the
Company has agreed to compensate  the Bank Facility  Guarantors,  principally in
the form of 1 million  additional  warrants  and  repricing  and  extending  the
expiration date of 5.5 million warrants  previously issued  (together,  the "New
Guarantee  Warrants").  The New  Guarantee  Warrants will be on the same pricing
terms as those issued as part of the Units.  The Bank Facility  Guarantors  will
have  certain  demand and  piggy-back  registration  rights  with  regard to the
unregistered  shares of the Company's Common Stock held by them or issuable upon
exercise of the Guarantee Warrants.

Further,  in connection with the Guarantee Issuance  Agreement,  the Company has
agreed  to  reimburse  the  Bank  Facility  Guarantors  in the  event  that  the
Guarantors  are required to make payment  under the  Revolving  Credit  Facility


                                      F-11

<PAGE>


guarantees,  and, in connection with this Reimbursement  Commitment has provided
the Bank  Facility  Guarantors a junior  security  interest  with respect to the
assets of the Company, principally its stockholdings in AMRC and the Acquisition
Company.




Motorola Vendor Financing

Motorola has agreed to provide the Acquisition  Company with up to $10.0 million
of vendor financing (the "Vendor Financing Commitment"), which will be available
to finance up to 75% of the purchase price of additional  network base stations.
Loans under this  facility will bear interest at a rate equal to LIBOR plus 7.0%
and will be  guaranteed by the Company and each  subsidiary  of the  Acquisition
Company.  The terms of such  facility  will  require  that  amounts  borrowed be
secured by the  equipment  purchased  therewith.  This  commitment is subject to
customary  conditions,  including due  diligence,  and there can be no assurance
that the facility will be obtained by the Acquisition  Company on these terms or
at all.

Summary of Recent Financing

The Company believes the proceeds from the issuance of the Notes,  together with
the borrowings under the New Bank Financing and the Vendor Financing Commitment,
will be sufficient to pay the cash portion of the Acquisition and fund operating
losses,  capital  expenditures,  working  capital,  and scheduled  principal and
interest  payments on debt through the time when the Company expects to generate
positive  free  cash flow  (operating  cash  flow  less  capital  expenditures);
however,  there  can be no  assurance  that the  Company's  current  projections
regarding the timing of its ability to achieve positive operating cash flow will
be  accurate,  and that the Company  will not need  additional  financing in the
future. See "Overview."

At December 31,  1997,  the Company had  remaining  contractual  commitments  to
purchase both mobile data  terminal  inventory  and mobile  telephone  inventory
approximating  $6.3  million.  (See  Note  10  to  the  consolidated   financial
statements).

All wholly owned subsidiaries of the Company are subject to financing agreements
that limit the amount of cash  dividends  and loans that can be  advanced to the
Company.  At  December  31,  1997,  all of these  subsidiaries'  net assets were
restricted under these  agreements.  These  restrictions  will have an impact on
American Mobile's ability to pay dividends.

Cash used in operating  activities was $50.9 million for 1997 compared to $113.6
million  for  1996.  The  decrease  in cash  used in  operating  activities  was
primarily  attributable to (i) decreased  operating  losses,  and (ii) decreased
inventory and accounts receivable  balances.  Cash used by investing  activities
was $10.2 million for 1997 compared to cash provided by investing  activities of
$50.9  million in 1996.  The $61.1  decrease was primarily  attributable  to the
proceeds in the amount of $66.0  million from the  settlement  of the  Company's
claims under its satellite insurance contracts and policies, offset by a general


                                      F-12

<PAGE>


reduction in capital  expenditures.  Cash provided by financing  activities  was
$61.1 million in 1997 compared to cash used of $56.0 million in 1996, reflecting
the proceeds from the Bank Financing,  offset by the repayment of certain vendor
financing and other  long-term  debt.  Proceeds from the sale of debt securities
and Common Stock were $284,000 and $2.9 million for 1997 and 1996, respectively.
Payments  on  long-term  debt and  capital  leases  were $8.8  million and $63.2
million for 1997 and 1996, respectively. In addition, the Company incurred $10.8
million  of debt  issuance  costs  associated  with  the  placement  of the Bank
Financing in 1996, as compared to $1.5 million in 1997. As of December 31, 1997,
the Company had $2.1 million of cash and cash equivalents and working capital of
$5.3 million.


Regulation

The ownership and operations of the Company's  communication systems are subject
to significant  regulation by the FCC, which acts under authority granted by the
Communications Act of 1934, as amended (the  "Communications  Act"), and related
federal laws. A number of the  Company's  licenses are subject to renewal by the
FCC and,  with respect to the  Company's  satellite  operations,  are subject to
international  frequency  coordination.  In  addition,  current FCC  regulations
generally  limit the  ownership  and  control  of  American  Mobile by  non-U.S.
citizens  or  entities  to 25%.  There can be no  assurances  that the rules and
regulations  of the FCC will  continue to support the  Company's  operations  as
presently  conducted and contemplated to be conducted in the future, or that all
existing  licenses will be renewed and requisite  frequencies  coordinated.  See
"Part I, Item 1. Business - Regulation".

On June 5, 1996,  the FCC  granted  ARDIS  extensions  of time to  complete  the
buildouts  of 190 antenna  sites,  as required  to maintain  previously  granted
licenses.  As of March 25,  1998,  approximately  104 of the sites  remain to be
constructed  by  expiration  dates that range between June 27, 1998 to March 31,
1999. Management estimates that $5.2 million will be necessary to achieve timely
buildouts of the network, including $5.0 million in 1998. Failure to obtain such
capital or to complete the  buildouts in a timely manner could result in loss of
licenses  for  such  sites  from  the  FCC,  loss of  customers,  as well as the
incurrence of penalties under a customer  contract,  which would have a material
adverse effect on the Company.


Other Matters

As previously  reported,  the satellite  has, in the past,  experienced  certain
technological  anomalies,  most  significantly  with respect to its eastern beam
which resulted in the Company's  receipt of $66.0 million of insurance  proceeds
as discussed  above (see  "Liquidity  and Capital  Resources").  There can be no
assurance that the satellite will not experience subsequent anomalies that could
adversely impact the Company's  financial  condition,  results of operations and
cash flows. See "Part I, Item 1. Business-Satellite Back-up and Technology".


                                      F-13

<PAGE>



Regarding the year 2000 compliance  issue for information  systems,  the Company
has  recognized  the need to ensure that its computer  operations  and operating
systems will not be adversely affected by the upcoming calender year 2000 and is
cognizant of the time sensitive nature of the problem.  The Company has assessed
how  it  may  be  impacted  by  year  2000  and  has  formulated  and  commenced
implementation of a comprehensive plan to address known issues as they relate to
its  information  systems.  The plan,  as it  relates  to  information  systems,
includes a combination of  modification,  upgrade and  replacement.  The Company
estimates that the cost of year 2000 compliance for its information systems will
not have a material  adverse  affect on the future  consolidated  results of the
operations  of the Company.  The Company is not yet able to estimate the cost of
year 2000 compliance with respect to third party suppliers;  however, based on a
preliminary  review,  management  does not  expect  that such  costs will have a
material  adverse  effect  on the  Company's  financial  condition,  results  of
operations and cash flow.


Accounting Standards

In  March  1997,  the  Financial  Accounting  Standards  Board  ("FASB")  issued
Statement of Financial  Accounting  Standards  ("SFAS") No. 128,  "Earnings  per
Share." This  Statement  governs the  calculation of Earnings per Share ("EPS"),
and requires that EPS  calculations be presented as Basic Earnings per Share and
Diluted Earnings per Share. The impact of adopting the Statement is not material
to the financial statements.

In June 1997,  the FASB issued SFAS No. 130,  "Reporting  Comprehensive  Income"
governing the reporting and display of comprehensive  income and its components,
and SFAS No.  131,  "Disclosures  about  Segments of an  Enterprise  and Related
Information"  requiring that public  businesses report financial and descriptive
information  about  its  reportable  operating  segments.  Both  Statements  are
applicable to reporting periods beginning after December 15, 1997. The impact of
adopting  the  Statements  is not  expected  to be  material  to  the  financial
statements.



                                      F-14

<PAGE>




   Report of Independent Public Accountants


To American Mobile Satellite Corporation:

We have audited the accompanying  consolidated balance sheets of American Mobile
Satellite  Corporation (a Delaware  corporation) and Subsidiaries as of December
31,  1997  and  1996,   and  the  related   consolidated   statements  of  loss,
stockholders'  equity and cash  flows for each of the three  years in the period
ended December 31, 1997. These financial  statements are the  responsibility  of
the Company's  management.  Our responsibility is to express an opinion on these
financial statements based on our audits.

We  conducted  our  audits  in  accordance  with  generally   accepted  auditing
standards.  Those standards  require that we plan and perform an audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement.  An audit includes examining, on a test basis, evidence supporting
the amounts and disclosure in the financial  statements.  An audit also includes
assessing the  accounting  principles  used and  significant  estimates  made by
management,  as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

In our opinion,  the financial  statements  referred to above present fairly, in
all material  respects,  the  financial  position of American  Mobile  Satellite
Corporation  and  Subsidiaries as of December 31, 1997 and 1996, and the results
of their  operations  and their  cash  flows for each of the three  years in the
period ended December 31, 1997, in conformity with generally accepted accounting
principles.



/s/Arthur Andersen LLP

Washington, D.C.
March 31, 1998


                                      F-15

<PAGE>
<TABLE>


American Mobile Satellite Corporation and Subsidiaries

Consolidated  Statements of Loss  (dollars in thousands,  except per share data)
for the years ended December 31, 1997, 1996, and 1995


<CAPTION>


                                                    Years Ended December 31
                                           ----------------------------------------------

<S>                                               <C>             <C>              <C> 
                                                     1997             1996            1995

REVENUES
 Services                                           $20,684          $9,201          $6,873
 Sales of equipment                                  23,530          18,529           1,924
                                                     ------          ------          ------

 Total Revenues                                      44,214          27,730           8,797

COSTS AND EXPENSES:
 Cost of service and operations                      31,959          30,471          23,948
 Cost of equipment sold                              40,335          31,903           4,676
 Sales and advertising                               12,066          24,541          22,775
 General and administrative                          14,819          17,464          16,681
 Depreciation and amortization                       42,430          43,390          11,218
                                                     ------          ------          ------

 Operating Loss                                     (97,395)       (120,039)        (70,501)

INTEREST EXPENSE                                    (21,633)        (15,151)           (916)
INTEREST AND OTHER  INCOME                            1,122             552           4,500 
EQUITY IN LOSS OF AMRC                               (1,301)             --              --
                                                    --------        --------           -----

NET LOSS                                          ($119,207)      ($134,638)       ($66,917)
                                                  ==========      ==========       =========

BASIC AND DILUTED LOSS PER SHARE OF COMMON STOCK     ($4.74)         ($5.38)         ($2.69)



WEIGHTED-AVERAGE COMMON SHARES
 OUTSTANDING DURING THE PERIOD (000's)               25,131          25,041          24,900




The  accompanying  notes are an integral  part of these  consolidated  financial
statements.

</TABLE>


                                      F-16

<PAGE>
<TABLE>

American Mobile Satellite Corporation and Subsidiaries

Consolidated Balance Sheets (dollars in thousands,  except per share data) as of
December 31, 1997 and 1996

<CAPTION>
<S>                                                                         <C>                 <C>   
ASSETS                                                                         1997                1996
                                                                               ----                ----
CURRENT ASSETS:
  Cash and cash equivalents                                                   $2,106              $2,182
  Inventory                                                                   40,321              38,034
  Prepaid in-orbit insurance                                                   4,564               5,080
  Accounts receivable-trade, net of allowance for doubtful accounts            8,140               6,603
     of $1,930 in 1997 and $1,548 in 1996
  Other current assets                                                         9,608              14,247
                                                                              ------              ------
  Total current assets                                                        64,739              66,146

PROPERTY AND EQUIPMENT IN SERVICE - NET
  (gross balances include $135,586 and $134,737 purchased from
        related parties through 1997 and 1996 respectively)                  233,174             267,863

DEFERRED CHARGES AND OTHER ASSETS:
  (net of accumulated amortization of $14,096 in 1997 and 
     $10,597 in 1996)
  (gross balances include $3,000 paid to related parties in 1996)             13,534              16,164
                                                                             -------              ------

  Total assets                                                              $311,447            $350,173
  ------------                                                              ========            ========

LIABILITIES AND STOCKHOLDERS' EQUITY

CURRENT LIABILITIES:
  Accounts payable and accrued expenses                                      $35,861             $42,625
  Obligations under capital leases due within one year                           798               3,931
  Current portion of long-term debt                                           15,254              11,113
  Other current liabilities                                                    7,520                  --
                                                                             -------             -------

  Total current liabilities                                                   59,433              57,669

LONG-TERM LIABILITIES:
  Obligations under Bank Financing                                           198,000             127,000
  Capital lease obligations                                                    3,147               2,557
  Net assets acquired in excess of purchase price (Note 12)                    2,725               3,395
  Other long-term debt                                                         1,364                  --
  Other long-term liabilities                                                    647                 852
                                                                               -----                 ---

  Total long-term liabilities                                                205,883             133,804
                                                                             -------             -------

  Total liabilities                                                          265,316             191,473

COMMITMENTS (Note 9 and 10)

STOCKHOLDERS' EQUITY:
 Preferred Stock, par value $0.01: authorized 200,000 shares;
     no shares issued                                                             --                  --
 Common Stock, voting, par value $0.01: authorized 75,000,000 shares;
     25,159,311 shares issued and outstanding in 1997; 25,097,577 shares
     issued and outstanding in 1996                                              252                 251
 Additional paid-in capital                                                  451,892             451,259
 Common Stock purchase warrants                                               36,338              23,848
 Unamortized guarantee warrants                                              (23,586)            (17,100)
 Retained loss                                                              (418,765)           (299,558)
                                                                            ---------           ---------
 Total stockholders' equity                                                   46,131             158,700
                                                                              ------             -------

 Total liabilities and stockholders' equity                                 $311,447            $350,173
 ------------------------------------------                                 ========            ========

The  accompanying  notes are an integral  part of these  consolidated  financial
statements.
</TABLE>

                                      F-17

<PAGE>


<TABLE>

American Mobile Satellite Corporation and Subsidiaries

Consolidated  Statements of Stockholders'  Equity (dollars in thousands,  except
per share data) for the period from January 1, 1995 through December 31, 1997
<CAPTION>

                                                Common Stock    Additional     Common Stock Unamortized
                                                   Shares      Par   Paid-in     Purchase    Guarantee  Retained
                                                              Value  Capital     Warrants     Warrants     Loss      Total
<S>                                             <C>          <C>    <C>         <C>       <C>         <C>         <C>     
- ------

BALANCE, December 31, 1994                      24,798,755   $248   $445,859     $3,440         --     ($98,003)  $351,544
 Common Stock issued in January under         
  Stock Purchase Plan                                8,707     --         94         --         --         --           94
 Common Stock issued in April pursuant 
  to Launch Services Contract                       81,909      1      1,719         --         --         --        1,720
 Common Stock issued throughout the year 
  for exercise of stock options and award           32,026      1        518         --         --         --          519
  of bonus stock
 Common Stock issued in July under Stock            22,170     --        238         --         --         --          238
  Purchase Plan
 Common Stock issued in March, June, 
  September and December under the 401(k)   
  Savings Plan                                      17,563     --        329         --         --         --          329
 Net Loss                                               --     --         --         --         --      (66,917)   (66,917)
                                                ----------    ---    -------      -----      -----    ---------    --------
BALANCE, December 31, 1995                      24,961,130    250    448,757      3,440         --     (164,920)   287,527

 Common Stock issued in January under 
  Stock Purchase Plan                               13,432     --        294         --         --         --          294
 Common Stock purchase warrants issued
  in January for Bridge Financing                       --     --         --      2,253         --         --        2,253
 Common Stock issued for exercise of   
  stock options and award of bonus stock            37,320     --        612         --         --         --          612
 Common Stock issued upon exercise of Warrants      37,500      1        844       (845)        --         --           --
 Common Stock purchase warrants issued in               --     --         --     19,000    (19,000)        --           --
   July for Bank Financing 
 Amortization of guarantee warrants                     --     --         --         --      1,900         --        1,900
 Common Stock issued in July under Stock            25,934     --        341         --         --         --          341
  Purchase Plan
 Common Stock issued in March, June, 
  September and December under the 401(k)
  Savings Plan                                      22,261     --        411         --         --         --          411
 Net Loss                                               --     --         --         --         --     (134,638)  (134,638)
                                                ----------    ---    -------      -----      -----    ---------   ---------
BALANCE, December 31, 1996                      25,097,577    251    451,259     23,848    (17,100)    (299,558)   158,700

 Common stock issued in March, June,         
  September, October, and December under 
  the 401K Saving Plan                              31,684       1       349         --         --         --          350
 Common stock issued in January and 
  July under the Stock Purchase Plan                29,930      --       283         --         --         --          283
 Common Stock issued throughout award 
  of bonus stock                                       120      --         1         --         --         --            1
 Stock Purchase Warrants Revaluation                    --      --        --     12,490    (12,490)        --           --
 Amortization of Stock Purchase  
  Warrants                                              --      --        --         --      6,004         --        6,004
 Net Loss                                               --      --        --         --         --     (119,207)  (119,207)
                                                ----------     ---   -------      -----      -----    ---------   ---------
BALANCE, December 31, 1997                      25,159,311    $252  $451,892    $36,338   ($23,586)   ($418,765)   $46,131
                                                ==========    ====  ========    =======   =========   ==========   =======




The  accompanying  notes are an integral  part of these  consolidated  financial
statements.
</TABLE>


                                      F-18

<PAGE>
<TABLE>
American Mobile Satellite Corporation and Subsidiaries

Consolidated Statements of Cash Flows (dollars in thousands) for the years ended
December 31, 1997, 1996, and 1995
<CAPTION>
                                                                                         Years Ended December 31
                                                                                    ----------------------------------

                                                                                       1997        1996        1995
                                                                                       ----        ----        ----

CASH FLOWS FROM OPERATING ACTIVITIES:
<S>                                                                                 <C>         <C>          <C>
Net loss                                                                            ($119,207)  ($134,638)   ($66,917)
Adjustments to reconcile net loss to net cash used in operating activities:
   Amortization of guarantee warrants, debt discount, and debt issuance costs           9,350       5,721          --
   Depreciation and amortization                                                       42,430      43,307      11,218
   Equity in loss from AMRC                                                             1,301          --          --
   Changes in assets and liabilities:
     Inventory                                                                         (2,287)    (27,482)    (10,438)
     Prepaid in-orbit insurance                                                           516        (257)     (4,823)
     Trade accounts receivable                                                         (1,537)     (5,229)        218
     Other current assets                                                               4,639       1,970      (4,230)
     Accounts payable and accrued expenses                                             (5,820)      1,672      23,414
     Deferred trade payables                                                           11,685          --          --
     Deferred items - net                                                               8,038       1,347      (1,730)
                                                                                      --------   ---------    --------
Net cash used in operating activities                                                 (50,892)   (113,589)    (53,288)

CASH FLOWS FROM INVESTING ACTIVITIES:
Insurance proceeds applied to equipment                                                    --      66,000          --
Additions to property and equipment                                                    (8,598)    (14,054)    (83,776)
Proceeds from sales of short-term investments                                              --          --      28,717
Deferred charges and other assets                                                          --      (1,000)       (169)
Investment in AMRC                                                                     (1,643)         --          --
                                                                                       -------     ------     --------
Net cash provided by (used in) investing activities                                   (10,241)     50,946     (55,228)

CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of Common Stock                                                    284       1,247       2,569
Principal payments under capital leases                                                (2,576)     (3,994)       (538)
Proceeds from short-term borrowings                                                        --      70,000          --
Payments on short-term borrowings                                                          --     (70,000)         --
Proceeds from Bank Financing                                                           71,000     127,000          --
Proceeds from debt issuance                                                                --       1,700       7,630
Payments on long-term debt                                                             (6,180)    (59,190)    (28,486)
Debt issuance costs                                                                    (1,471)    (10,803)     (1,081)
                                                                                       -------    -------     --------
Net cash provided by (used in) financing activities                                    61,057      55,960     (19,906)


Net decrease in cash and cash equivalents                                                 (76)     (6,683)   (128,422)

CASH AND CASH EQUIVALENTS, beginning of period                                          2,182       8,865     137,287
                                                                                       ------     -------   ---------

CASH AND CASH EQUIVALENTS, end of period                                               $2,106      $2,182      $8,865
                                                                                       ======      ======      ======
Supplemental Cash Flow Information 
     Interest Payments                                                                $11,785      $8,293      $5,574

</TABLE>

The  accompanying  notes are an integral  part of these  consolidated  financial
statements.


                                      F-19

<PAGE>




AMERICAN MOBILE SATELLITE CORPORATION AND SUBSIDIARIES

Notes to Consolidated Financial Statements
as of December 31, 1997, 1996 and 1995


1. ORGANIZATION, BUSINESS AND LIQUIDITY

American Mobile Satellite Corporation (with its subsidiaries,  "American Mobile"
or the  "Company")  was  incorporated  on May 3, 1988,  by eight of the  initial
applicants for the mobile satellite services license,  following a determination
by the Federal Communications  Commission ("FCC") that the public interest would
be best served by granting the license to a consortium of all willing, qualified
applicants.  The FCC has authorized  American Mobile to construct,  launch,  and
operate a mobile satellite services system (the "Satellite Network ") to provide
a full range of mobile voice and data  services via  satellite to land,  air and
sea-based  customers  in a service area  consisting  of the  continental  United
States,  Alaska,  Hawaii,  Puerto Rico, the U.S.  Virgin Islands,  U.S.  coastal
waters,  international  waters and airspace and any foreign  territory where the
local  government  has  authorized  the  provision  of  service.  In March 1991,
American Mobile Satellite Corporation  transferred the mobile satellite services
license ("MSS license") to a wholly owned subsidiary, American Mobile Subsidiary
Corporation  ("AMSC  Subsidiary").  On April 7, 1995,  the Company  successfully
launched its first satellite ("MSAT-2"), from Cape Canaveral, Florida.

In late  1996,  the  Company  expanded  its mobile  data  business  through  the
acquisition  of  Rockwell  International  Corporation's  ("Rockwell")  dual mode
mobile  messaging and global  positioning and monitoring  service for commercial
trucking  fleets.  Rockwell was a private network  customer of the Company which
had purchased capacity from the Company on MSAT-2. See Note 12.

On December 31, 1997, the Company  entered into a Stock Purchase  Agreement (the
"Purchase Agreement") with Motorola, Inc. ("Motorola"), for the acquisition (the
"Acquisition") of ARDIS Company ("ARDIS"), a wholly-owned subsidiary of Motorola
that owns and operates a two-way wireless data communications  network.  Subject
to certain purchase price adjustment provisions,  the Company will acquire ARDIS
for a purchase  price of $50  million in cash and $50  million in the  Company's
Common Stock and  warrants  (the  "Purchase  Price").  The Company,  through the
acquisition  of ARDIS,  intends  to create a  nationwide  provider  of  wireless
communications services, including data, dispatch, and voice services, primarily
to business customers in the United States. See Note 15.

On October 16, 1997,  American Mobile Radio Corporation,  an indirect subsidiary
of American  Mobile through its subsidiary  AMRC Holdings,  Inc.  (together with
American Mobile Radio Corporation,  "AMRC"), was awarded a license by the FCC to
provide  satellite-based  Digital Audio Radio Service  ("DARS")  throughout  the
United States, following its successful $89.9 million bid at auction on April 2,



                                      F-20

<PAGE>

1997.  American  Mobile has entered  into an  agreement  with  WorldSpace,  Inc.
("WorldSpace"),  by which  WorldSpace has acquired a 20%  participation in AMRC,
which can dilute the Company's  interest in AMRC to 28%. In connection  with the
DARS  auction,  AMRC has also  arranged for financing of the FCC license fees as
well as for initial  working  capital  needs,  which  financing has included the
issuance of  options.  AMRC has and will  continue  to receive  funding for this
business from an independent  source in exchange for debt and an equity interest
in AMRC.  Accordingly,  it is not expected that the development of this business
will have a material  impact on the  Company's  financial  position,  results of
operations, or cash flows. See Note 2.

                                      F-21

<PAGE>




American Mobile is devoting its efforts to expanding a developing business. This
effort involves  substantial risk,  including  successfully  integrating  ARDIS.
Specifically,  future operating results will be subject to significant business,
economic,    regulatory,    technical,   and   competitive   uncertainties   and
contingencies. Depending on their extent and timing, these factors, individually
or in the  aggregate,  could have an adverse  effect on the Company's  financial
condition and future results of operations.


Liquidity and Financing Requirements

Adequate  liquidity  and capital  are  critical to the ability of the Company to
continue  as a  going  concern  and  to  fund  subscriber  acquisition  programs
necessary to reach cash positive and profitable operations.  The Company expects
to continue to make  significant  capital outlays for the foreseeable  future to
fund interest  expense,  capital  expenditures  and working capital prior to the
time that it begins to generate  positive cash flow from  operations and for the
foreseeable future thereafter.  To fund its operations through the first quarter
of 1998, the Company (i) borrowed all remaining amounts available under the Bank
Financing,  (ii) entered into a $10 million  Bridge Loan  Agreement (the "Bridge
Loan") with Hughes Communications Satellite Services, Inc. ("Hughes"), and (iii)
arranged the financing of $11.7 million of deferred trade payables. See Note 7.

The Company  currently  believes that the net proceeds from the sale of the $335
million  in Notes and  warrants,  together  with the  borrowings  under the $200
million New Bank Financing,  the Motorola  financing,  and the proceeds from the
Satellite Lease  Agreement (all discussed  below) will be sufficient to meet the
Company's currently anticipated capital expenditures,  operating losses, working
capital and debt service requirements  through 1998 and beyond.  However, if the
Company's cash flows from  operations are less than  projected,  the Company may
not meet its  financial  performance  agreements  under  the  Guaranty  Issuance
Agreement and, if such  conditions are not met or waived,  the Company would not
have access to additional funds under the Revolving  Credit  Facility.  See Note
15. In addition, even in the event that the Company has access to such funds, it
may  require  additional  debt or equity  financing  in  amounts  that  could be
substantial.  The type,  timing and terms of  financing  selected by the Company
will be dependent  upon the  Company's  cash needs,  the  availability  of other
financing sources and the prevailing conditions in the financial markets.  There
can be no  assurance  that any such  sources will be available to the Company at
any given time or as to the favorableness of the terms on which such sources may
be available.

In connection  with the ARDIS  Acquisition,  the Company  raised $335 million in
cash proceeds from the private issuance of units ("Units") consisting of 12 1/4%
Senior Notes  ("Notes") due 2008 and one warrant to purchase  3.75749  shares of
Common  Stock of the  Company  for each $1,000  principal  amount of Notes,  and
restructured its existing Bank Financing the "New Bank Financing"). The New Bank
Financing of $200 million  will  consist of a $100 million  unsecured  five-year
reducing  Revolving  Credit Facility  maturing March 31, 2003 and a $100 million



                                      F-22

<PAGE>

five-year  Term Loan Facility with up to three  additional  one-year  extensions
subject to lender  approval.  Additionally,  Motorola  has agreed to provide the
Company  with up to $10  million  of vendor  financing  ("the  Vendor  Financing
Commitment"), which will be available to finance up to 75% of the purchase price
of additional base stations needed to meet ARDIS'  buildout  requirements  under
certain customer contracts. See Note 15.

On December 4, 1997, the Company entered into two simultaneous transactions. The
Company  agreed  with TMI to  acquire a  one-half  ownership  interest  in TMI's
satellite, MSAT-1, at a cost of $60 million payable in equal installments over a
five-year  period  (the  "Satellite  Purchase  Agreement");  certain  additional
payments  to TMI are  contemplated  in the event that  additional  benefits  are
realized by the Company.  Simultaneously,  the Company entered into an agreement
(the "Satellite Lease  Agreement") with African  Continental  Telecommunications
Ltd. ("ACTEL"), for the lease of MSAT-2, for deployment over sub-Saharan Africa.
The  five-year  lease  provides for aggregate  lease  payments to the Company of
$182.5 million.  The lease includes a renewal option through the end of the life
of MSAT-2.  Closing under the Satellite  Purchase  Agreement and Satellite Lease
Agreement  is  subject to a number of  conditions.  It is  anticipated  that the
closing under both leasing agreements will occur simultaneously in the spring of
1998.  See Note 10.


2. SIGNIFICANT ACCOUNTING POLICIES

Development Stage Company

Consistent  with  Statement of Financial  Accounting  Standards  ("SFAS") No. 7,
"Accounting and Reporting by Development Stage  Enterprises," the Company ceased
to be considered a development  stage company in the fourth quarter of 1996 with
the generation of significant revenue from its voice products and services.


Accounting Estimates

The preparation of financial  statements in conformity  with generally  accepted
accounting   principles  (GAAP)  requires   management  to  make  estimates  and
assumptions  that affect the reported  amount of assets and  liabilities  at the
date of the  financial  statements  and the  reported  amounts of  revenues  and
expenses  during the reporting  period.  Actual  results could differ from those
estimates.  The Company's most significant  estimates relate to the valuation of
inventory  and  committed  inventory  purchases  and the  allowance for doubtful
accounts receivable.


Consolidation

The consolidated  financial  statements  include the accounts of American Mobile
and  seven of its  wholly  owned  subsidiaries,  one of which is  inactive.  All
significant  inter-company  transactions and accounts have been  eliminated.  As
discussed in Note 1, AMRC, was awarded a license to provide  digital audio radio
service  ("DARS") and entered into an  agreement  with World Space, Inc. ("World



                                      F-23

<PAGE>

Space"),  whereby World Space has acquired a 20%  participation in AMRC, and the
exercise of outstanding  issued options could reduce American Mobile's ownership
interest in AMRC to 28%.  Additionally,  the agreement gives WorldSpace  certain
participative  rights  which  provide  for their  participation  in  significant
business  decisions  that  would be made in the  ordinary  course  of  business;
therefore, in accordance with Emerging Issues Task Force ("EITF") No. 96-16, the
Company's investment in AMRC is carried on the equity method.

The following represents the unaudited summary financial  information of AMRC as
of December 31,1997. AMRC had no material activity prior to 1997.

  (In thousands)
  Current assets              $     --      Gross sales                $   --
  Noncurrent assets             91,901      Operating expense           1,110
  Current liabilities               --      Interest expense              518
  Noncurrent liabilities        84,387      Net loss                    1,628
  Total stockholders' equity     7,514





Cash and Cash Equivalents 

The Company considers highly liquid investments with remaining  maturities of 90
days or  less at the  time of  acquisition  to be cash  equivalents.  


Inventories

Inventories,  which consist primarily of finished goods, are stated at the lower
of cost or market.  Cost is determined  using the weighted  average cost method.
The Company  periodically  assesses the market value of its inventory,  based on
sales trends and  forecasts  and  technological  changes and records a charge to
current  period  income  when such  factors  indicate  that a  reduction  to net
realizable  value is appropriate.  For purposes of evaluating the net realizable
value of inventory,  management  considers  both inventory on hand and inventory
which it has committed to purchase.  During 1997 and 1996, the Company  recorded
charges  to Cost of  Equipment  Sold in the  amount of $12.0  million  and $11.1
million,  respectively,  related to the realizability of the Company's inventory
investment.


Fair Value of Financial Instruments

SFAS No. 107, "Disclosures about Fair Value of Financial  Instruments," requires
disclosures of the fair value of certain financial instruments.  For purposes of


                                      F-24

<PAGE>


this disclosure, the fair value of a financial instrument is the amount at which
the  instrument  could be exchanged  in a current  transaction  between  willing
parties.  Cash and cash  equivalents,  trade  accounts  receivable  and accounts
payable approximate fair value because of the relatively short maturity of these
instruments. As a result of the Guarantees (see Note 7) associated with the Bank
Financing,  it is not  practicable  to estimate the fair value of this facility.
The fair value of other debt  approximates  carrying  value  because the related
debt has variable interest costs based on current market rates or are short-term
in nature.


Concentrations of Credit Risk

Financial instruments which potentially subject the Company to concentrations of
credit risk  consist  principally  of  temporary  cash  investments,  short-term
investments  and accounts  receivable.  The Company  places its  temporary  cash
investments  and short-term  investments in debt  securities  such as commercial
paper,  time  deposits,   certificates  of  deposit,  bankers  acceptances,  and
marketable  direct  obligations  of the United  States  Treasury.  The Company's
intent is to hold its investments in debt  securities to maturity.  To date, the
majority of the Company's business has been transacted with  telecommunications,
natural resources and transportation companies,  including maritime and trucking
companies located  throughout the United States. The Company grants credit based
on an  evaluation  of the  customer's  financial  condition,  generally  without
requiring  collateral  or  deposits.   Exposure  to  losses  on  trade  accounts
receivable,  for both service and for inventory sales, is principally  dependent
on each customer's financial condition.  The Company anticipates that its credit
risk with respect to trade accounts receivable in the future will continue to be
diversified  due to the large  number of  customers  expected  to  comprise  the
Company's base and their expected  dispersion  across many different  industries
and geographies.

Software Development Costs

The Company  capitalizes costs related to the development of certain software to
be used with its mobile  messaging  and position  location  service (the "Mobile
Data  Communications  Service") product.  The Company commenced  amortization of
these costs in the first  quarter of 1996.  These costs will be  amortized  over
three  years.  As of  December  31,  1997 and  1996,  net  capitalized  software
development  costs were $1.8  million and $3.6  million,  respectively,  and are
included in property and equipment in the accompanying balance sheets.


Deferred Charges and Other Assets

Other assets  primarily  consist of unamortized  financing  costs and debt issue
costs  associated with the existing vendor  financing  arrangements and the Bank
Financing.  The  Company  had $11.8  million  and $14.9  million of  unamortized
financing costs recorded at December 31, 1997 and 1996, respectively.  Financing
costs are  amortized  over the term of the related  facility  using the straight
line method, which approximates the effective interest method.




                                      F-25

<PAGE>



Revenue Recognition

The Company  recognizes service revenue when  communications  services have been
rendered.  Equipment sales are recognized upon shipment of products and customer
acceptance, if required.


Research and Development Costs

Research and  development  costs are expensed as  incurred.  Such costs  include
internal  research  and  development  activities  and expenses  associated  with
external product development agreements.  The Company did not incur any research
and  development  cost for 1997,  and  incurred  approximately  $57,000 and $1.8
million for 1996 and 1995, respectively.


Advertising Costs

Advertising  costs are charged to  operations  in the year  incurred and totaled
$3.4 million,  $6.0  million,   and  $6.5  million  for  1997,  1996,  and  1995
respectively.

Stock Based Compensation

The Company  accounts for employee  stock options using the method of accounting
prescribed by APB Opinion No. 25,  "Accounting  for Stock Issued to  Employees."
Generally,  no expense is  recognized  related to the  Company's  stock  options
because the option's  exercise  price is set at the stock's fair market value on
the date the option is granted.  Effective  January 1, 1996, the Company adopted
SFAS No. 123 by making the required footnote disclosures (see Note 5).


Assessment of Asset Impairment

SFAS No.  121  "Accounting  for the  Impairment  of  Long-Lived  Assets  and for
Long-Lived  Assets to be Disposed of" requires that  impairment  losses for such
assets  be based  upon the fair  value of the  assets,  and was  adopted  by the
Company as the primary  basis by which the Company  measures  impairment  of the
Satellite Network and its related components. Adoption of this Statement has not
resulted in the  recording of a provision for  impairment of long-lived  assets,
but there can be no assurance that a material  provision for impairment will not
be required in the future.


Loss Per Share

In 1997,  the Company  adopted SFAS No. 128,  "Earnings Per Share." SFAS No. 128
requires dual  presentation of basic and diluted  earnings per share on the face
of the income  statement  for all periods  presented.  Basic  earnings per share
excludes  dilution  and is  computed  by  dividing  income  available  to common
stockholders by the weighted-average number of common shares outstanding for the
period.

                                      F-26

<PAGE>



Diluted  earnings per share reflects the potential  dilution that could occur if
securities or other contracts to issued common stock were exercised or converted
into common stock.  Options and warrants to purchase shares of common stock were
not  included  in the  computation  of loss  per  share as the  effect  would be
antidilutive.  As a result, the basic and diluted earnings per share amounts are
identical.



3. STOCKHOLDERS' EQUITY

The Company has  authorized  200,000  shares of Preferred  Stock and  75,000,000
shares of  Common  Stock.  The par  value  per share is $0.01 for each  class of
stock.  For each share held,  Common  stockholders  are  entitled to one vote on
matters  submitted  to the  stockholders.  Cumulative  voting  applies  for  all
elections of directors of the Company.

The Preferred Stock may be issued in one or more series at the discretion of the
Board of Directors (the "Board"),  without  stockholder  approval.  The Board is
authorized   to  determine   the  number  of  shares  in  each  series  and  all
designations, rights, preferences, and limitations on the shares in each series,
including,  but not limited to, determining whether dividends will be cumulative
or non-cumulative.

Certain   controlling   stockholders   of  the  Company   have  entered  into  a
Stockholders'  Agreement (the "Agreement") which contains provisions relating to
the election of directors,  procedures for maintaining compliance with the FCC's
alien ownership  restrictions,  certain  restrictions on the transfer,  sale and
exchange  of Common  Stock,  and  procedures  for  appointing  directors  to the
Executive  Committee of the Board,  among  others.  The  Agreement  continues in
effect until  terminated by an affirmative  vote of holders of  three-fourths of
the  Company's  Common  Stock held by parties to the  Agreement.  Other  matters
relating  to the  Company's  governance  of the  Company  are set  forth  in the
Certificate of Incorporation and Bylaws.


As of  December  31,  1997,  the Company had  reserved  Common  Stock for future
issuance as detailed below.


Shares issuable upon exercise of warrants                              6,474,596
Amended and Restated Stock Option Plan for Employees                   3,429,326
Stock Option Plan for Non-Employee Directors                              50,000
Employee Stock Purchase Plan                                             190,137
Defined Contribution Plan                                                103,492
                                                                         -------
        Total                                                         10,247,551
                                                                      ==========


4. PROPERTY AND EQUIPMENT

Property and equipment is recorded at cost and depreciated  over its useful life
using the straight line method.  Assets recorded as capital leases are amortized
over the shorter of their useful lives or the term of the lease.

                                      F-27

<PAGE>



The estimated  useful lives of office  furniture  and  equipment  vary from 2-10
years,  and the  Communications  Ground Segment  ("CGS") is  depreciated  over 8
years.

The Company is depreciating  the Space Segment over its estimated useful life of
10 years,  which was based on several factors,  including current conditions and
the estimated  remaining fuel of MSAT-2.  The original  estimated useful live is
periodically  reviewed  using current  Telemetry  Tracking and Control  ("TT&C")
data. To date, no significant  change in the original  estimated useful life has
resulted.  The  telecommunications  industry  is subject to rapid  technological
change  which may require the Company to revise the  estimated  useful  lives of
MSAT-2 and the CGS or to adjust  their  carrying  amounts.  The Company has also
capitalized  certain  costs to develop and implement  its  computerized  billing
system.  These costs are included in property and equipment and are  depreciated
over 8 years. Certain amounts from 1996 have been restated in the summary below.

The costs of constructing and putting satellites into service are capitalized in
the financial  statements and depreciated  over the estimated useful life of the
satellite. A total failure of the satellite from unsuccessful launches and/or in
orbit  anomalies  would result in a current  write-down of the satellite  value.
Partial  satellite  failures are recognized  currently to the extent such losses
are deemed  abnormal to the operation of the satellite.  A partial failure which
is deemed normal would not result in a loss of satellite capacity beyond what is
considered  normal  satellite  wear and tear and thus, a write down would not be
required.  Additionally,  all  future  incentive  arrangements  relating  to the
construction of satellites will be capitalized at launch.



Property and equipment consists of the following:

                                                               December 31
(in thousands)                                            1997            1996

Space Segment                                           $187,976        $187,386
Ground Segment                                           109,691         104,559
Office equipment and furniture                            19,305          16,684
Mobile Data Communications Service                        21,118          21,014
                                                          ------          ------
                                                         338,090         329,643
Less accumulated depreciation and amortization           104,916          61,780
                                                         -------          ------
Property and equipment, net                             $233,174        $267,863
                                                        ========        ========


5. STOCK OPTIONS

The Company has two active stock option  plans.  The American  Mobile  Satellite
Corporation  1989 Amended and  Restated  Stock  Option Plan for  Employees  (the
"Plan") permits the grant of non-statutory  options and the award of bonus stock


                                      F-28

<PAGE>


up to a total of 3.5  million  shares of  Common  Stock.  Under  the  Plan,  the
exercise   price  and  vesting   schedule  for  options  is  determined  by  the
Compensation  Committee of the Board,  which was  established  to administer the
Plan. Generally, options vest over a three year period and will have an exercise
price not less than the fair  market  value of a share on the date the option is
granted  or have a term  greater  than ten years.  In March  1997,  the  Company
repriced  certain  employee stock options to $13.00 per share. No other terms of
the options were modified.

The  Company  also has a Stock  Option  Plan  for  Non-Employee  Directors  (the
"Director Plan") which provides for the grant of options up to a total of 50,000
shares of Common Stock.  Directors  receive an initial  option to purchase 1,000
shares of Common  Stock,  with annual  option  grants to purchase  500 shares of
Common Stock.  Options under the Director Plan can be exercised at a price equal
to the fair  market  value of the  stock on the date of the  grant and are fully
vested and  immediately  exercisable  on the date of grant.  Each  Director Plan
option  expires  on the  earlier of (i) ten years from the date of grant or (ii)
seven months after the Director's termination.

In January 1998,  the Board of Directors  granted  356,111  shares of restricted
stock to senior  management  for the first time.  These  grants  include  both a
three-year vesting schedule as well as specific corporate  performance  targets.
Unless waived by the Board of Directors,  failure to meet a required performance
target would prevent the vesting of the restricted shares.


Information regarding the Company's stock option plans is summarized below:

<TABLE>
<CAPTION>

                                                                                                     Weighted Average
                                                                Available            Granted and     Option Price Per
                                                                for Grant            Outstanding          Share

<S>                                                            <C>                    <C>                 <C>   
Balance, December 31, 1994                                        349,878                407,776          $18.60
  Additional shares authorized for grant                           50,000                    ---            --
  Granted                                                        (275,480)               275,480           16.88
  Exercised and awarded                                                --                (32,026)          16.10
  Forfeited                                                        60,380                (60,380)          18.50
                                                                   ------                --------               
Balance, December 31, 1995                                        184,778                590,850           17.94
  Additional shares authorized for grant                        1,241,138                     --            --
  Granted                                                      (1,565,272)             1,565,272           18.37
  Exercised and awarded                                                --                (37,320)          16.41
  Forfeited and canceled                                          623,356               (623,356)          23.23
                                                                  -------               ---------          
Balance, December 31, 1996                                        484,000              1,495,446           16.22
  Additional shares authorized for grant                        1,500,000                     --            --
  Granted                                                      (1,292,443)             1,292,443           12.67
  Exercised and awarded                                                --                   (120)          10.28
  Forfeited                                                     1,104,828             (1,104,828)          17.15
                                                                ---------             -----------          
Balance, December 31, 1997                                      1,796,385              1,682,941          $13.08
                                                                =========             ===========



</TABLE>

                                      F-29

<PAGE>



<TABLE>
Options Exercisable at December 31:
<CAPTION>
                           Options                 Average
                                                Exercise Price

<S>                        <C>                      <C>   
1997                       595,432                  $14.39
1996                       276,804                  $17.97
1995                       219,272                  $18.31
1994                       175,471                  $17.73
</TABLE>

The  Company  accounts  for  stock  compensation  costs in  accordance  with the
provisions of Accounting  Principles Board Opinion No. 25, "Accounting for Stock
Issued to Employees." Had  compensation  cost been determined  based on the fair
value  at the  grant  dates  for  awards  under  the  Company's  stock  plans in
accordance  with SFAS No. 123,  the net loss would have been  increased  by $5.3
million  ($.21 per  share) and $2.3  million  ($.09 per share) in 1997 and 1996,
respectively.  As required by SFAS No. 123,  the fair value of each option grant
is estimated on the date of grant using the  Black-Scholes  option pricing model
with the following  assumptions for 1997 and 1996: no historical dividend yield;
an expected  life of 10 years;  historical  volatility of 65% in 1997 and 45% in
1996, 45% and a risk-free  rate of return ranging from 5.71% to 6.44%.  Exercise
prices for options outstanding as of December 31, 1997, are as follows:

<TABLE>
<CAPTION>

                                 Options Outstanding                                          Options Exercisable
                            Number               Weighted                                  Number
                        Outstanding as            Average             Weighted        Exercisable as of       Weighted
      Range of         of December 31,           Remaining            Average           December 31,           Average
  Exercise Prices            1997            Contractual Life      Exercise Price           1997           Exercise Price

<S>                       <C>                       <C>                 <C>               <C>                  <C>   
    9.06 - 12.00            471,500                 8.82                $11.45            132,160              $11.84
   12.50 - 12.81            476,585                 9.07                 12.74                --                 0.00
   13.00 - 13.00            549,808                 7.64                 13.00            278,224               13.00
   14.62 - 26.25            185,048                 5.47                 18.29            185,048               18.29
                            -------                                                       -------               
   $9.06 - $26.25         1,682,941                 8.14                $13.08            595,432              $14.39
                          =========                                                       =======
</TABLE>


6. INCOME TAXES

The Company  accounts for income taxes under the liability method as required in
the Statement of Financial  Accounting Standards No. 109, "Accounting for Income
Taxes." Under the liability method, deferred income taxes are recognized for the
tax consequences of "temporary  differences" by applying  enacted  statutory tax
laws and rates  applicable to future years to differences  between the financial
statement carrying amounts and the tax bases of existing assets and liabilities.
Under  this  method,  the effect on  deferred  taxes of a change in tax rates is
recognized in income in the period that includes the enactment  date.  Potential
tax benefits,  related to net operating losses and temporary  differences,  have
been  recorded as an asset,  and a valuation  allowance  for the same amount has
been established. The Company has paid no income taxes since inception.

                                      F-30

<PAGE>



The following is a summary of the Company's net deferred tax assets.
<TABLE>


                                                                December 31
<CAPTION>
(in thousands)                                             1997             1996

<S>                                                      <C>              <C>     
Net Operating Loss for Income Tax Purposes               $217,918         $170,710
Deferred Taxes Related to Temporary Differences:
  Tangible asset bases, lives and depreciation methods    (65,898)         (64,889)
  Other                                                     8,700            6,229
                                                            -----            -----
Total deferred tax asset                                  160,720          112,050
Less valuation allowance                                 (160,720)        (112,050)
                                                         ---------        ---------
Net deferred tax asset                                   $     --         $     --
                                                         =========        =========
</TABLE>

Significant  timing  differences  affecting  deferred  taxes  in 1997  were  the
treatment of costs  associated  with the Space Segment for  financial  reporting
purposes compared to tax purposes.  As of December 31, 1997, the Company had net
operating loss carryforwards  ("NOLs") of $542 million. The NOLs expire in years
2004 through 2012. These NOL carryforwards are subject to certain limitations if
there is determined  to be a  substantial  change in ownership as defined in the
Internal Revenue Code.


7. LONG-TERM DEBT


                                                   December 31
(in thousands)                                1997             1996

Bank Financing                              $198,000         $127,000
Deferred Payment Agreement                        --            5,180
Deferred Trade Payables                       11,685               --
Term Loan Agreement                            4,933            5,933
                                               -----            -----
                                             214,618          138,113
Less current maturities                       15,254           11,113
                                              ------           ------
Long-term debt                              $199,364         $127,000
                                            ========         ========

Bank Financing - Term Loan and Working Capital Facility

On  June  28,  1996,  established  a  $219  million  debt  facility  (the  "Bank
Financing"),  of which $200 million is available and fully guaranteed by certain
American  Mobile  shareholders.  As of December  31,  1997,  the Bank  Financing
consisted of: (i) a $144 million  five-year,  multi-draw term loan facility (the
"Term Loan Facility") with quarterly payments  commencing March 31, 1999 through
and including June 30, 2001, and (ii) a $56 million  five-year  revolving credit
facility  with a  bullet  maturity  on  June  30,  2001  (the  "Working  Capital
Facility").  Proceeds from the Bank  Financing  were used to repay the Company's
interim financing and to refinance short-term Vendor Financing, and will be used


                                      F-31

<PAGE>


for general  working  capital  purposes.  As of March 20, 1998,  the Company had
drawn down $144.0  million of the Term Loan  Facility at annual  interest  rates
ranging from 6.025% to 6.0875% and $56.0 million of the Working Capital Facility
at annual interest rates ranging from 6.025% to 6.2125%.  The Company,  on March
27, 1997,  reached an agreement  with the  Guarantors  to eliminate all covenant
tests in exchange for additional warrants and a repricing of warrants previously
issued (together,  the "Guarantee Warrants").  As a result of the repricing, the
Guarantee  Warrants were revalued at $21.9 million,  effective March 27,1997 and
are being amortized over the remaining life of the guarantee. On March 31, 1998,
in connection with the  Acquisition,  the Bank Financing was  restructured.  See
Note 15.


Deferred Trade Payables

In the last quarter of 1997, the Company arranged the financing of certain trade
payables. As of December 31, 1997, $11.7 million of deferred trade payables were
outstanding at rates ranging from 6.23% to 14% and are generally  payable by the
end of 1998.


Bridge Loan

On  December  31,  1997,  the  Company  entered  into a Bridge  Loan with Hughes
Communications Satellite Services, Inc. ("Hughes") in the principal amount of up
to $10 million,  secured by a pledge of the Company's  interest in its 80%-owned
subsidiary, AMRC. The Bridge Loan bears an annual interest rate of 12% and has a
maturity date of March 31, 1999, and requires  mandatory  repayment in the event
net proceeds are received from any asset disposition, lease agreement, financing
or equity  transaction  of the  Company.  The Bridge  Loan was drawn in full and
subsequently  repaid in full on March 31,  1998,  with a portion of the proceeds
from the Notes.  No further  borrowing is available  under the Bridge Loan.  See
Note 15.


Term Loan Agreement

The Company  entered  into a Term Loan  Agreement  (the "Loan  Agreement")  with
Northern Telecom to finance the purchase of certain  equipment to be used in the
ground segment.  The Loan Agreement provided for principal borrowings up to $7.5
million plus $1.1 million for accrued  interest.  In September 1996, the Company
arranged to reduce the interest  rate from LIBOR plus 4.5% to a floating rate of
LIBOR  plus  2.5%  through  maturity  and to defer  amounts  due  under the Loan
Agreement  to1997.  In December 1997, the Loan Agreement was amended to increase
the interest rate to LIBOR plus 4.5%,  effective January 1, 1998, and to defer a
portion of principal payments until April 1, 1998. As of December 31, 1997, $4.9
million was outstanding at an annual interest rate of 8.156%.




                                      F-32

<PAGE>



Deferred Payment Agreement

In 1992, the Company entered into a contract ("CGS Contract") with  Westinghouse
Electric  Corporation   ("Westinghouse")  pursuant  to  which  Westinghouse  was
responsible for designing and constructing the Ground Segment and developing the
final specification for mobile telephones.  In connection with the CGS Contract,
Westinghouse agreed to defer payment,  including interest thereon, under certain
terms and  conditions,  for the basic  purchase  price and for change orders and
options elected by the Company (the "Deferred Payment Agreement").  During 1997,
the remaining $5.2 million  obligation under the Deferred Payment  Agreement was
fully repaid.


Interest Costs

The Company  incurred  interest  costs of  approximately  $21.6  million,  $15.1
million,  and $5.6 million in 1997, 1996, and 1995,  respectively.  All interest
costs  incurred  through  September  30,  1995 were  capitalized  as part of the
Company's   construction   activities.   The   capitalization  of  interest  was
discontinued in the fourth quarter of 1995 when the Satellite Network was deemed
substantially  complete and ready for its intended use.  Interest cost paid, net
of amounts capitalized, was $ 327,000 in 1995.


Assets Pledged and Secured

All wholly owned subsidiaries of the Company are subject to financing agreements
that limit the amount of cash  dividends  and loans that can be  advanced to the
Company.  At  December  31,  1997,  all of the  subsidiaries'  net  assets  were
restricted under these  agreements.  These  restrictions  will have an impact on
American Mobile Satellite Corporation's ability to pay dividends.


Covenants

The debt agreements and related Guarantee Agreements entered into by the Company
contain various restrictions,  covenants, defaults, and requirements customarily
found in such financing agreements.  Among other restrictions,  these provisions
include  limitations on cash dividends,  restrictions  on  transactions  between
American  Mobile and its  subsidiaries,  restrictions  on capital  acquisitions,
material  adverse  change  clauses,   and  maintenance  of  specified  insurance
policies.


8. RELATED PARTIES

In 1990,  following a competitive bid process,  American Mobile signed contracts
with Hughes  Aircraft,  the parent  company of Hughes  Communications  Satellite
Services ("Hughes Communications"), an American Mobile stockholder, to construct
MSAT-2 (the "Satellite  Construction  Contract").  The contract  contains flight
performance  incentives  payable  by the  Company to Hughes  Aircraft  if MSAT-2
performs according to the contract.  The total incentives owed, if earned,  will


                                      F-33

<PAGE>


be $7.1 million,  plus  interest,  with payment  amounts  otherwise due deferred
until second quarter 1998.  The costs of the  incentives are  capitalized in the
period  earned.  The Company  also in 1990  selected  HNS Ltd.,  an affiliate of
Hughes Aircraft, to design, manufacture, and implement the Company's Mobile Data
Communications  Service.  In 1991,  the Company  entered into an agreement  with
Hughes  Communications to provide assistance in the launch services  procurement
process  and  certain  other  management   services  through  the  launch  date.
Additionally,  in 1996,  Hughes  loaned the Company $10.0 million as part of its
participation  in the Interim  Financing.  On  December  31,  1997,  the Company
entered  into  a  Bridge  Loan   Agreement   (the  "Bridge  Loan")  with  Hughes
Communications in the principal amount of up to $10 million (see Note 7).

The Company has entered into various transactions and agreements with affiliates
of  AT&T  Wireless  Services,   Inc.  ("AT&T  Wireless"),   an  American  Mobile
stockholder.  The  arrangements  include the purchase of satellite  capacity and
equipment by AT&T, the purchase by American Mobile of certain  equipment for use
in the  Satellite  Network,  the leasing of certain  office  equipment,  and the
engagement  of  AT&T  to  be  one  of  the  Company's  long-distance  providers.
Additionally,  the Company sublet certain office space to AT&T Wireless  through
September  1996.  The  following  table  presents  a summary  of  related  party
transactions.
<TABLE>
<CAPTION>


                                                                               Years Ended December 31
(in thousands)                                                            1997                1996                1995

<S>                                                                    <C>                 <C>                  <C>
Payments made to (from) related parties:
Additions to property under construction                               $    --             $    --              $3,029
Additions to property and equipment in service                             200               2,847                 265
Proceeds from debt issuance                                                 --             (10,000)                 --
Payments on debt obligations                                               292              20,926                 251
Payment for Guarantees                                                      --               3,000                  --
Operating expenses                                                       2,706               3,817               1,453
Satellite capacity/airtime revenue                                      (2,836)             (1,276)                 --
Sublease income                                                             --                (205)               (239)
Other                                                                       --                  --                (506)
                                                                       --------            --------             -------
Net payments to related parties                                        $   362             $19,109              $4,253
                                                                       ========            ========             =======
Due to (from) related parties:
Mobile Data Communications Service Financing                           $    --             $    --              $7,180
Capital leases                                                             249                 446                 631
Operating expenses                                                       1,209                 185                 708
Satellite capacity/airtime revenue                                        (495)               (416)                 --
Capital acquisitions                                                     2,120               1,584               1,924
                                                                         -----               -----               -----
Net amounts due to related parties                                     $ 3,083              $1,799             $10,443
                                                                       ========            ========            ========

</TABLE>




                                      F-34

<PAGE>



 9. LEASES

Capital Leases

The Company leases certain office  equipment and Ground Segment  equipment under
agreements accounted for as capital leases. Assets recorded as capital leases in
the accompanying balance sheets include the following:


                                                           December 31
(in thousands)                                         1997          1996

Ground Segment equipment                              $7,263        $7,263
Office equipment                                       4,033         4,088
Less accumulated amortization                          4,750         2,826
                                                       -----         -----
Total                                                 $6,546        $8,525
                                                      ======        ======      

Amortization of the Ground Segment equipment began with the commencement of full
commercial service in December 1995.

In January 1996, the Company  refinanced  certain computer  hardware  components
under a sale/leaseback arrangement.  The Company received proceeds in the amount
of $1.7 million.  The transaction was accounted for as a financing,  wherein the
property  remains on the books and  continues  to be  depreciated.  A  financing
obligation  representing  the proceeds  was  recorded,  and is reduced  based on
payments under the lease.  The  sale/leaseback  has a three-year  term and had a
balance of approximately $93,000 at December 31, 1997.


Operating Leases

The Company leases certain facilities and equipment under arrangements accounted
for as operating leases.  Certain of these  arrangements have renewal terms. The
office lease has an original  lease term of ten years  expiring in 2003,  with a
renewal option, and escalation clauses.  Total rent expense, under all operating
leases,  approximated  $2.9 million,  $2.5  million,  and $10.6 million in 1997,
1996, and 1995, respectively.



                                      F-35

<PAGE>



At December  31,  1997,  minimum  future  lease  payments  under  noncancellable
operating and capital leases are as follows:


                                Operating            Capital
                                 Leases               Leases
(in thousands)
1998                             $2,188               $1,200
1999                              2,114                2,124
2000                              2,044                1,351
2001                              2,085                   --
2002                              2,131                   --
thereafter                        2,155                   --
- ----------                        -----                -----
Total                           $12,717               $4,675
                                =======               
Less: Interest                                           730
                                                       -----
                                                      $3,945
                                                      ======


10. OPERATING AGREEMENTS AND COMMITMENTS

Joint Operating and Satellite Capacity Agreements

On December 4, 1997, the Company entered into two simultaneous transactions. The
Company  agreed  with TMI to  acquire a  one-half  ownership  interest  in TMI's
satellite, MSAT-1, at a cost of $60 million payable in equal installments over a
five-year  period  (the  "Satellite  Purchase  Agreement");  certain  additional
payments  to TMI are  contemplated  in the event that  additional  benefits  are
realized  by the  Company.  Under  the  Satellite  Purchase  Agreement,  TMI and
American Mobile will each own a 50% undivided  ownership  interest in the Shared
Satellite,  will  jointly  be  responsible  for  the  operation  of  the  Shared
Satellite,  and  will  share  certain  satellite  operating  expenses,  but will
otherwise  maintain  their separate  business  operations.  Simultaneously,  the
Company entered into an agreement (the "Satellite Lease Agreement") with African
Continental  Telecommunications  Ltd.  ("ACTEL"),  for the lease of MSAT-2,  for
deployment over sub-Saharan  Africa.  The five-year lease provides for aggregate
lease  payments to the Company of $182.5  million.  The lease includes a renewal
option  through  the end of the life of  MSAT-2,  on the same  lease  terms,  at
ACTEL's  election  exercisable 2 1/2 years prior to the end of the initial lease
term.

Should the Satellite  Purchase  Agreement and Satellite  Lease  Agreement not be
consummated,  the  Company  and TMI will  remain  parties  to a Joint  Operating
Agreement and a Satellite  Capacity  Agreement  under which the parties agree to
provide,  among other  things,  emergency  backup and restoral  services to each
party  during  any  period in which the  other's  satellite  is not  functioning
properly.  Additionally,  each party will be entitled to lease  excess  capacity
from the other party's  satellite  under  specified  terms and  conditions.  The
implementation of these agreements requires regulatory  approvals by the FCC and


                                      F-36

<PAGE>


Industry  Canada  (formerly  Canada's  Department of Industry and Science).  The
Company has  received,  and expects to continue to seek  approvals  contemplated
under these agreements on a timely basis.


Commitments

At December 31,  1997,  the Company had  remaining  contractual  commitments  to
purchase both mobile data  terminal  inventory  and mobile  telephone  inventory
approximating $6.3 million.

The aggregate fixed and  determinable  portion of all inventory  commitments and
obligations for other fixed contracts for the next five years is as follows.


(in thousands)

1998                                             $7,011
1999                                              1,802
2000                                                426
                                                    ---
Total                                            $9,239
                                                 ======

Additionally, the Company may enter into additional commitments that may require
the purchase of mobile  telephone and mobile terminal  inventory in amounts that
could be material to the Company's financial condition.

The Company entered an agreement with a vendor,  whereby the Company would incur
extra licensing fees, up to a total maximum potential of $4.1 million,  upon the
voice subscriber base reaching certain levels.  Management does not believe that
the subscriber levels outlined in the license will be met.



11. EMPLOYEE BENEFITS

Defined Contribution Plan

The Company sponsors a 401(k) defined  contribution plan ("401(k) Savings Plan")
in which all employees can  participate.  Effective  January 1, 1995, the 401(k)
Savings Plan provides for a Company match of employee contributions, in the form
of Common  Stock,  limited to the fair  market  value of up to  one-half  of the
employee's  contribution not to exceed 6% of an employee's salary. The Company's
matching expense was $350,000 for 1997, $411,000 for 1996 and $329,000 for 1995.






                                      F-37

<PAGE>



Employee Stock Purchase Plan

In December 1993,  the Company  adopted the Employee Stock Purchase Plan ("Stock
Purchase Plan") to allow eligible  employees to purchase shares of the Company's
Common Stock at 85% of the lower of market value on the first and last  business
day of the six-month  option period.  An aggregate of 29,930,  39,366 and 30,877
shares of Common Stock were issued under the Stock Purchase Plan in 1997,  1996,
and 1995, respectively.


12.  BUSINESS ACQUISITION

On November 22, 1996, the Company acquired the assets of Rockwell Collins,  Inc.
("Rockwell")   relating   to  its   Land   Transportation   Electronics   Mobile
Communications   Satellite  Service  business  (the  "Business")  through  which
Rockwell had sold mobile messaging hardware and services to commercial  trucking
fleets.  The assets of the Business  were  acquired  from  Rockwell  through the
assumption by the Company of the various  contracts and  obligations of Rockwell
relating to the Business;  no additional  direct payments were made or are to be
made under the terms of the Asset Sale Agreement, dated as of November 22, 1996.
The assets of the business  acquired from Rockwell include  tangible  equipment,
completed  inventory  and future  inventory  deliveries to be used in connection
with fulfilling the contracts transferred with the Business. The Company intends
to continue such use in operating the Business.

The purchase  method of  accounting  for  business  combinations  was used.  The
operating   results  of  the  Business  have  been  included  in  the  Company's
consolidated   statements  of  loss  from  the  date  of  acquisition  and  were
insignificant  in 1996.  The fair value of the assets  acquired was $9.5 million
and liabilities assumed totaled $6.1 million.  The fair value of assets acquired
in excess of purchase  price arising from the  acquisition in the amount of $3.4
million is being  amortized  over five years on a straight  line  basis.  Assets
acquired included inventory  deliveries,  fixed assets, and other  miscellaneous
items.

The pro forma results below (unaudited)  assume the acquisition  occurred at the
beginning of the year ended December 31, 1996 (dollars in thousands,  except per
share data).


                                            1996

Revenue                                   $33,333
Net Loss                                 (148,434)
Loss per share                              (5.93)





                                      F-38

<PAGE>



13. LEGAL AND REGULATORY AND OTHER MATTERS

Legal and Regulatory Matters

Like other mobile  service  providers in the  telecommunications  industry,  the
Company is subject to substantial domestic, foreign and international regulation
including the need for regulatory  approvals to operate and expand the Satellite
Network and operate and modify subscriber equipment.

The  successful  operation of the Satellite  Network is dependent on a number of
factors,  including the amount of L-band  spectrum made available to the Company
pursuant  to  an  international  coordination  process.  The  United  States  is
currently  engaged in an  international  process of  coordinating  the Company's
access to the  spectrum  that the FCC has  assigned  to the  Company.  While the
Company  believes that  substantial  progress has been made in the  coordination
process and expects that the United  States  government  will be  successful  in
securing the necessary spectrum,  the process is not yet complete. The inability
of the United States  government  to secure  sufficient  spectrum  could have an
adverse effect on the Company's  financial  position,  results of operations and
cash flows.

The Company has the necessary regulatory  approvals,  some of which are pursuant
to  special  temporary  authority,  to  continue  its  operations  as  currently
contemplated.  The  Company has filed  applications  with the FCC and expects to
file applications in the future with respect to the continued operations, change
in  operation  and  expansion  of the Network and  certain  types of  subscriber
equipment.  Certain of its  applications  pertaining to future service have been
opposed.  While the Company, for various reasons,  believes that it will receive
the necessary  approvals on a timely basis,  there can be no assurance  that the
requests  will be granted,  will be granted on a timely basis or will be granted
on  conditions  favorable  to  the  Company.  Any  significant  changes  to  the
applications resulting from the FCC's review process or any significant delay in
their approval could adversely affect the Company's financial position,  results
of operations and cash flows.

The Company's  license  requires that it comply with a  construction  and launch
schedule specified by the FCC for each of the three authorized  satellites.  The
second  and  third  satellites  are not in  compliance  with  the  schedule  for
commencement of construction.  The Company has asked the FCC to grant extensions
of the deadlines for the second and third satellites. Certain of these extension
requests  have  been  opposed  by third  parties.  The FCC has not  acted on the
Company's  requests.  The FCC has the authority to revoke the authorizations for
the second and third  satellites and in connection  with such  revocation  could
exercise its authority to rescind the Company's  license.  The Company  believes
that the exercise of such authority to rescind the license is unlikely.

As a provider of interstate telecommunications services, the Company is required
to contribute to the FCC's universal  service fund, which supports the provision
of  telecommunication  services to  high-cost  areas,  and  establishes  funding
mechanisms  to support the provision of service to schools,  libraries and rural
health care providers.  The regulation became effective on January 1, 1998. This
cost  is not  born by the  Company,  but is  passed  on to its  customers  as is
universally practiced in the industry.


                                      F-39

<PAGE>



In 1992, a former director of American Mobile filed an Amended Complaint against
the Company alleging  violations of the  Communications Act of 1934, as amended,
and of the Sherman Act and breach of  contract.  The suit seeks  damages for not
less than $100 million  trebled under the antitrust laws plus punitive  damages,
interest,  attorneys fees and costs. In mid-1992, the Company filed its response
denying all  allegations.  The Company's motion for summary  judgment,  filed on
March  31,  1994,  was  denied  on April 18,  1996.  The  trial in this  matter,
previously  set for December 1997, has been postponed to a date to be determined
in 1998.  Management  believes that the ultimate outcome of this matter will not
be material to the Company's financial  position,  results of operations or cash
flows.


Other Matters

As previously  reported,  the satellite  has, in the past,  experienced  certain
technological anomalies, most significantly with respect to its eastern beam. On
August 1,  1996,  the  Company  reached a  resolution  of the  claims  under its
satellite  insurance  contracts and policies and received proceeds in the amount
of $66.0  million  which were used to repay the  Working  Capital  Facility  and
portions of the Term Loan  Facility and the Vendor  Financing.  Based on certain
engineering  studies and the design of the satellite,  the Company believes that
the  insurance  proceeds  reflected  the actual cost of damage  sustained to the
satellite,  and, as a result, the carrying value of the satellite was reduced by
the net insurance proceeds, which resulted in a reduction of future depreciation
charges  beginning in the third quarter of 1996.  There can be no assurance that
the satellite will not  experience  subsequent  anomalies  that could  adversely
impact the Company's financial condition, results of operations and cash flows.

The Company has received a current  recommendation  from a subcontractor  to its
satellite   manufacturer   that,   pending   further  results  from  an  ongoing
investigation,  the satellite  should be operated at modified  power  management
levels. The Company and its satellite  manufacturer are investigating the basis,
if any, for this  recommendation.  Based on the  information  available to date,
management  believes  that,  even if  maintained,  the current power  management
recommendation  would  not have a  material  negative  effect  on the  Company's
business plan within the next three to five years, based on anticipated  traffic
patterns and anticipated  subscriber  levels. In the event that traffic patterns
or subscriber levels materially exceed those  anticipated,  the power management
recommendation,  if  maintained,  could have a material  impact on the Company's
long-term business plan.




                                      F-40

<PAGE>



14. SUPPLEMENTAL CASH FLOW INFORMATION

<TABLE>
<CAPTION>

                                                                                          Years Ended December 31
(in thousands)                                                                       1997          1996           1995

<S>                                                                                <C>           <C>            <C>   
Noncash investing and financing activities:
Leased asset and related obligations                                                 $182          $284         $1,351
Issuance of Common Stock purchase warrants                                         12,490        21,253             --
Issuance of Common Stock upon exercise of Common
  Stock purchase warrants                                                              --           845             --
Vendor financing for property under construction                                       --            --          7,561
Vendor financing for property in service                                               --         2,440          4,560
Issuance of Common Stock under the Defined Contribution Plan                          349           411            329
Net assets acquired as a result of Business Acquisition (Note 12)                      --         3,488             --
</TABLE>


NOTE 15 - SUBSEQUENT EVENTS

During  the  first  quarter  of 1998,  the  Company  entered  into a  series  of
transactions. These transactions, some of which contain certain contingencies to
closing,  include the  acquisition of ARDIS and related $335 million  financing;
the restructuring of the Bank Financing; and a commitment by Motorola to provide
the Company with up to $10 million of vendor financing  related to the build out
of the ARDIS network.


Stock Purchase Agreement and Related Financing

As discussed in Note 1, on December 31, 1997,  the Company  entered into a Stock
Purchase  Agreement  with  Motorola  for the  acquisition  of ARDIS,  a Motorola
subsidiary  that  owns and  operates  a  two-way  wireless  data  communications
network.   Subject  to  certain   post-acquisition   purchase  price   reduction
provisions,  the Company would acquire ARDIS for a purchase price of $50 million
in cash and $50 million in the Company's stock and warrants. The transaction was
subject to certain governmental  approvals,  including FCC approvals to transfer
the ARDIS  licenses  to the  Company,  and was  subject to the  completion  of a
financing  by the  Company  in an  amount  sufficient  to fund the  transactions
contemplated  under the Stock  Purchase  Agreement.  On March 3,  1998,  the FCC
granted  consent to  consummate  the  Acquisition,  and on March 31,  1998,  the
Acquisition was consummated.


$335 Million Unit Offering

In  connection  with the  Acquisition,  the  Company  formed a new  wholly-owned
subsidiary ("Acquisition Company") to hold the stock of all current wholly-owned
operating  subsidiaries,   acquire  ARDIS,  and  issue  $335  million  of  Units
consisting of 12 1/4% Senior Notes due 2008 of Acquisition Company, and Warrants
to purchase shares of Common Stock of the Company.  Each Unit consists of $1,000




                                      F-41

<PAGE>

principal  amount of Notes and one Warrant to purchase  3.75749 shares of Common
Stock at an exercise price of $12.51 per share. A portion of the net proceeds of
the sale of the Units were used to finance the Acquisition.  The Notes are fully
guaranteed  by American  Mobile  Satellite  Corporation.  The terms of the Notes
require  that the Company  purchase a portfolio  of U.S.  government  securities
(approximately $113 million), which will provide funds sufficient to pay in full
when due the first six scheduled semi-annual interest payments on the Notes. The
Company  intends to use the  remaining  proceeds  from the Notes to fund certain
required escrows, repay the Bridge Loan, repay certain deferred obligations, pay
expenses associated with the Acquisition and the $335 Million Unit Offering,  to
repay the Revolving  Credit Facility under the Bank  Financing,  and for working
capital requirements.


New Bank Financing

In connection with the Acquisition, the Company, the Acquisition Company and its
subsidiaries  restructured  the existing $200 million Bank  Financing to provide
for the New Bank Financing:  (i) the Revolving Credit  Facility,  a $100 million
unsecured  five-year reducing revolving credit facility,  and (ii) the Term Loan
Facility,  a $100  million  five-year,  term  loan  facility  with  up to  three
additional one-year  extensions subject to the lenders' approval.  The Revolving
Credit Facility will be the obligation of Acquisition Company and will rank pari
passu with the Notes.  The Term Loan Facility will be the obligation of American
Mobile Satellite Corporation and is secured by the stockholdings of the Company,
principally its stockholdings in AMRC and the Acquisition  Company,  and will be
effectively subordinated to the Revolving Credit Facility and the Notes. The New
Bank Financing is severally  guaranteed by Hughes,  Singapore  Telecom and Baron
Capital Partners,  L.P. (the "Bank Facility  Guarantors").  The Banks' placement
fee for the New Bank Financing is approximately $500,000.

The Revolving  Credit  Facility bears an interest rate,  generally,  of 50 basis
points above LIBOR and is unsecured, with a negative pledge on the assets of the
Acquisition Company and its subsidiaries  ranking pari passu with the Notes. The
Revolving  Credit  Facility will be reduced $10 million each quarter,  beginning
with the quarter ending June 30, 2002, with the balance due on maturity of March
31, 2003. Certain proceeds received by the Acquisition Company would be required
to repay and reduce the Revolving  Credit  Facility,  unless otherwise waived by
the  Banks  and the Bank  Facility  Guarantors:  (1) 100% of  excess  cash  flow
obtained by the Acquisition Company; (2) the first $25.0 million net proceeds of
the lease or sale of MSAT-2 received by the Acquisition  Company, and thereafter
75% of the remaining  proceeds  received from such lease or sale (the  remaining
25% may be retained by the  Acquisition  Company for business  operations);  (3)
100% of the proceeds of any other asset sales by the  Acquisition  Company;  (4)
50% of the net proceeds of any  offerings of the  Acquisition  Company's  equity
(the  remaining  50% to be retained  by the  Acquisition  Company  for  business
operations);  and (5) 100% of any major casualty  proceeds.  At such time as the
Revolving  Credit Facility is repaid in full, and subject to satisfaction of the
restrictive  payments provisions of the Notes, any prepayment amounts that would
otherwise  have  been used to  prepay  the  Revolving  Credit  Facility  will be
dividended to the Company.

The Term Loan Facility  bears an interest  rate,  generally,  of 50 basis points
above  LIBOR and is  secured  by the  assets  of the  Company,  principally  its


                                      F-42

<PAGE>


stockholdings in AMRC and the Acquisition  Company. The Term Loan Agreement does
not include any scheduled  amortization until maturity, but does contain certain
provisions for  prepayment  based on certain  proceeds  received by the Company,
unless otherwise waived by the Banks and the Bank Facility Guarantors:  (1) 100%
of excess cash flow  obtained by the  Company;  (2) the first $25.0  million net
proceeds of the lease or sale of MSAT-2 received by the Company,  and thereafter
75% of the remaining  proceeds  received from such lease or sale (the  remaining
25% to be retained by the Acquisition Company for business operations); (3) 100%
of the  proceeds  of any other asset  sales by the  Company;  (4) 50% of the net
proceeds  of any  equity  offerings  of the  Company  (the  remaining  50% to be
retained  by the  Company for  business  operations);  and (5) 100% of any major
casualty  proceeds of the Company.  To the extent that the Term Loan Facility is
repaid, the aforementioned proceeds that would otherwise have been used to repay
the Term Loan Facility will be used to repay and reduce the commitment under the
Revolving Credit Facility.


The Guarantees

In connection  with the New Bank  Financing,  the Bank Facility  Guarantors have
agreed  to  extend  separate  guarantees  of  the  obligations  of  each  of the
Acquisition  Company  and the  Company  to the Banks,  which on a several  basis
aggregate  to $200  million.  In their  agreement  with each of the  Acquisition
Company and the Company (the "Guarantee Issuance Agreement"),  the Bank Facility
Guarantors  have  agreed to make  their  guarantees  available  for the New Bank
Financing.  The Guarantee  Issuance  Agreement will include  certain  additional
agreements of the Acquisition  Company and of the Company including with respect
to financial  performance of the  Acquisition  Company  relating to the ratio of
debt to EBITDA and service  revenue,  which,  if not met,  could, if not waived,
limit the Acquisition Company's ability to draw down on additional amounts under
the  Revolving  Credit  Facility  and  result  in a  default  under the New Bank
Financing  beginning in 1999. In exchange for the additional risks undertaken by
the Bank  Facility  Guarantors in connection  with the New Bank  Financing,  the
Company has agreed to compensate  the Bank Facility  Guarantors,  principally in
the form of 1 million  additional  warrants  and  repricing  and  extending  the
expiration date of 5.5 million warrants  previously issued  (together,  the "New
Guarantee Warrants").  The New Guarantee Warrants will be on terms substantially
similar, including with regard to pricing, as those issued as part of the Units.

Further,  in connection with the Guarantee Issuance  Agreement,  the Company has
agreed  to  reimburse  the  Bank  Facility  Guarantors  in the  event  that  the
Guarantors  are required to make payment  under the  Revolving  Credit  Facility
guarantees,  and, in connection with this Reimbursement  Commitment has provided
the Bank  Facility  Guarantors a junior  security  interest  with respect to the
assets of the Company, principally its stockholdings in AMRC and the Acquisition
Company.


Motorola Vendor Financing

Motorola has agreed to provide the Acquisition  Company with up to $10.0 million
of vendor financing (the "Vendor Financing Commitment"), which will be available
to finance up to 75% of the purchase price of additional  network base stations.
Loans under this  facility will bear interest at a rate equal to LIBOR plus 7.0%
and will be  guaranteed by the Company and each  subsidiary  of the  Acquisition


                                      F-43

<PAGE>


Company.  The terms of such  facility  will  require  that  amounts  borrowed be
secured by the  equipment  purchased  therewith.  This  commitment is subject to
customary  conditions,  including due  diligence,  and there can be no assurance
that the facility will be obtained by the Acquisition  Company on these terms or
at all.




NOTE 16 - FINANCIAL STATEMENTS OF SUBSIDIARIES

In connection with the Acquisition and related  financing  discussed in Note 15,
the Company formed a new wholly-owned subsidiary, AMSC Acquisition Company, Inc.
The Company  intends to transfer all of its rights,  title and interests in AMSC
Subsidiary  Corporation,  American Mobile Satellite Sales Corporation,  and AMSC
Sales Corp. Ltd. (together,  "American Mobile Subsidiaries") to AMSC Acquisition
Company, Inc.

AMSC Acquisition  Company,  Inc. will be the acquirer of ARDIS and the issuer of
the  $335  million  of  Senior  Notes.  American  Mobile  Satellite  Corporation
("Parent")  will  guarantee  the Senior  Notes.  The Senior  Notes will  contain
covenants  that,  among  other  things,  limit the  ability of AMSC  Acquisition
Company,  Inc. to incur  additional  indebtedness,  pay  dividends or make other
distributions,  repurchase any capital stock or subordinated indebtedness,  make
certain investments,  create certain liens, enter into certain transactions with
affiliates,  sell assets,  enter into certain  mergers and  consolidations,  and
enter into sale and leaseback transactions.

The combined condensed financial  statements of American Mobile Subsidiaries are
set forth below.



                                      F-44

<PAGE>



                          American Mobile Subsidiaries
                           Combined Statements of Loss
                             (dollars in thousands)
              for the years ended December 31, 1997, 1996, and 1995

<TABLE>
<CAPTION>

                                                     Years Ended December 31

                                              1997          1996         1995


REVENUES

<S>                                       <C>           <C>          <C>   
       Services                             $20,684        $9,201      $6,873
       Sales of equipment                    23,530        18,529       1,924
                                             ------        -------     ------

       Total Revenues                        44,214        27,730       8,797


COSTS AND EXPENSES:

       Cost of service and operations        31,959        30 471      23,863
       Cost of equipment sold                40,335        31,903       4,676
       Sales and advertising                 12,030        24,541      22,683
       General and administrative            14,890        16,212      17,285
       Depreciation and amortization         44,535        45,496      11,568
                                             ------        ------      ------

       Operating Loss                       (99,535)     (120,893)    (71,278)


INTEREST AND OTHER  INCOME                    1,122           552       1,242
INTEREST EXPENSE                            (51,153)      (44,636)     (3,305)
                                            --------      --------     -------

NET LOSS                                  $(149,566)    $(164,977)   $(73,341)
                                           =========      ========     =======  
</TABLE>




                                      F-45

<PAGE>



                          American Mobile Subsidiaries
                             Combined Balance Sheets
                             (dollars in thousands)
                        as of December 31, 1997 and 1996

<TABLE>
<CAPTION>
ASSETS                                                1997           1996


CURRENT ASSETS:

<S>                                                  <C>            <C>   
      Cash and cash equivalents                      $2,106         $2,182
      Inventory                                      40,321         38,034
      Prepaid in-orbit insurance                      4,564          5,080
      Accounts receivable-trade, net 
        of allowance for doubtful accounts            8,140          6,603
      Other current assets                            9,608         14,247
                                                      -----         ------
             Total current assets                    64,739         66,146

PROPERTY AND EQUIPMENT - NET                        250,335        287,127

DEFERRED CHARGES AND OTHER ASSETS:                   36,722         33,264
                                                     ------         ------

             Total assets                          $351,796       $386,537
                                                    =======        =======
LIABILITIES AND STOCKHOLDERS' EQUITY


CURRENT LIABILITIES:

      Accounts payable and accrued expenses         $35,825        $42,612
      Obligations under capital leases due 
        within one year                                 798          3,931
      Current portion of long-term debt              15,254         11,113
      Other current liabilities                       7,520             --
                                                      -----         ------
             Total current liabilities               59,397         57,656


DUE TO PARENT                                       441,836        400,831



LONG-TERM LIABILITIES:

      Obligations under Bank Financing              198,000        127,000
      Capital lease obligations                       3,147          2,557
      Net assets acquired in excess 
        of purchase price (Note 12)                   2,725          3,395
      Other long-term liabilities                     2,011            852
                                                    -------        -------

             Total long-term liabilities            205,883        133,804
                                                    -------        -------

             Total liabilities                      707,116        592,291
                                                    -------        -------

STOCKHOLDERS' EQUITY:                              (355,320)     (205,754)
                                                    -------       -------

             Total liabilities and 
               stockholders' equity                $351,796       $386,537
                                                   ========       ========

</TABLE>

                                      F-46

<PAGE>



                          American Mobile Subsidiaries
                   Combined Statements of Stockholders' Equity
                             (dollars in thousands)
          for the period from January 1, 1995 through December 31, 1997




                                      Total


BALANCE, December 31, 1994                                           $   32,564
    Net Loss                                                            (73,341)
                                                                        --------
BALANCE, December 31, 1995                                              (40,777)
    Net Loss                                                           (164,977)
                                                                        --------
BALANCE, December 31, 1996                                             (205,754)
    Net Loss                                                           (149,566)
                                                                        --------
BALANCE, December 31, 1997                                           $ (355,320)
                                                                       =========


                                      F-47

<PAGE>



                          American Mobile Subsidiaries
                        Combined Statements of Cash Flows
                             (dollars in thousands)
              for the years ended December 31, 1997, 1996, and 1995
<TABLE>
<CAPTION>


                                                                   Years Ended December 31
                                                          ------------------------------------------
                                                               1997          1996          1995

CASH FLOWS FROM OPERATING ACTIVITIES:
<S>                                                           <C>            <C>           <C>      
Net loss                                                      $(149,566)     $(164,977)    $(73,341)
Adjustments to reconcile net loss to net cash used in
operating activities:
             Amortization of debt discount                        9,350          5,721           --
             Depreciation and amortization                       44,535         45,413       11,568
             Changes in assets and liabilities:
                 Inventory                                       (2,287)       (27,482)     (10,438)
                 Prepaid in-orbit insurance                         516           (257)      (4,823)
                 Trade accounts receivable                       (1,537)        (5,229)         218
                 Other current assets                             4,639          1,970       (5,280)
                 Accounts payable and accrued expenses           (5,844)         1,668       23,414
                 Deferred trade payables                         11,685             --           --
                 Deferred items - net                             8,038          1,347       (1,730)
                                                                  -----          -----       -------

Net cash used in operating activities                           (80,471)      (141,826)     (60,412)
                                                                --------      ---------     --------


CASH FLOWS FROM INVESTING ACTIVITIES:
Insurance proceeds applied to equipment in service                   --         66,000           --
Additions to property and equipment                              (8,598)       (14,054)     (83,776)
Purchases of short-term investments                                  --         (1,000)          --
Deferred charges and other assets                                    --             --         (169)
                                                                 ------         ------      --------

Net cash provided by (used in) investing activities              (8,598)        50,946      (83,945)
                                                                -------        ------      --------

CASH FLOWS FROM FINANCING ACTIVITIES:

Funding from Parent                                              28,220         29,485      164,835
Principal payments under capital leases                          (2,576)        (3,994)        (538)
Proceeds from short-term borrowings                                  --         70,000           --
Payments on short-term borrowings                                    --        (70,000)          --
Proceeds from Bank Financing                                     71,000        127,000           --
Proceeds from debt issuance                                          --          1,700        7,630
Payments on long-term debt                                       (6,180)       (59,190)     (28,486)
Debt issuance costs                                              (1,471)       (10,803)      (1,081)
                                                                 -------       --------      -------

Net cash provided by (used in) financing activities              88,993         84,198      142,360

Net decrease in cash and cash equivalents                           (76)        (6,682)      (1,997)

CASH AND CASH EQUIVALENTS, beginning of period                    2,182          8,864       10,861
                                                                  -----          -----       ------
CASH AND CASH EQUIVALENTS, end of period                         $2,106         $2,182       $8,864
                                                                 ======         ======       ======

</TABLE>



                                      F-48

<PAGE>




                      QUARTERLY FINANCIAL DATA (unaudited)
                (dollars in thousands, except for per share data)

<TABLE>
<CAPTION>

                                                         1997-quarters                                     1996-quarters
                                      1st         2nd         3rd          4th         1st          2nd         3rd          4th
                                      ---         ---         ---          ---         ---          ---         ---          ---
<S>                                <C>          <C>         <C>          <C>        <C>          <C>         <C>          <C>   
Revenues                            $8,685      $10,753     $10,795      $13,981     $4,369       $6,749      $7,405       $9,207
Operating expenses(1)               32,341       32,420      30,617       46,231     31,371       45,747      33,914       36,737
Loss from operations               (23,656)     (21,667)    (19,822)     (32,250)   (27,002)     (38,998)    (26,509)     (27,530)
Interest and other 
  income (expense)                  (3,425)      (5,175)     (6,442)      (6,770)    (2,875)      (4,511)     (3,493)      (3,720)
Net Loss                           (27,081)     (26,842)    (26,264)     (39,020)   (29,877)     (43,509)    (30,002)     (31,250)
Net loss per common share (2)       $(1.08)      $(1.07)     $(1.04)      $(1.55)    $(1.20)      $(1.74)     $(1.20)      $(1.24)


Weighted-average common shares
outstanding during the 
  period (000s)                     25,109       25,120      25,145       25,151     24,995       25,012      25,065       25,092

Market price per share (3)
   High                             $14.75       $12.13      $10.88       $10.75     $33.25       $20.00      $17.50       $14.62
   Low                               $9.37        $8.50       $6.23        $6.28     $16.00       $15.00      $10.75        $9.25

</TABLE>



(1)  Operating  expenses  include charges of  approximately  $12  million in the
     fourth  quarter of 1997 and $11.1  million  in the  second  quarter of 1996
     related to the realizability of the Company's inventory investment.

(2)  Loss per  share  calculations  for each of the  quarters  are  based on the
     weighted average number of shares outstanding for each of the periods,  and
     the sum of the quarters may not  necessarily be equal to the full year loss
     per share amount.

(3)  The  Company's  Common  Stock is listed under the symbol SKYC on the Nasdaq
     National Market System.  The Company's Common Stock was not publicly traded
     prior  to  December  14,  1993.  The  quarterly  high and low  sales  price
     represents  the closing price in the Nasdaq  National  Market  System.  The
     quotations  represent  inter-dealer  quotations,  without  retail  markups,
     markdowns  or  commissions,   and  may  not  necessarily  represent  actual
     transactions.  As of February  28,  1998,  there were 251  stockholders  of
     record of the Company's Common Stock.

                                      F-49

<PAGE>



Selected Financial Data

Set forth  below is the  selected  financial  data for the  Company for the five
fiscal years ended December 31, 1997:

<TABLE>
<CAPTION>


(dollars in thousands, except for per share data)
                                                         1997          1996             1995          1994           1993
                                                         ----          ----             ----          ----           ----
<S>                                                  <C>           <C>               <C>           <C>              <C> 
Revenues                                               $44,214       $27,730           $8,797        $5,240           $852
Net Loss                                             $(119,207)    $(134,638)        $(66,917)     $(21,103)      $(25,180)
Net Loss per Common Share                               $(4.74)       $(5.38)          $(2.69)       $(0.86)        $(2.49)
Dividends on Common Stock (1)                             None          None             None          None           None
Consolidated Balance Sheet Data:
Cash and Cash Equivalents                               $2,106        $2,182           $8,865      $137,287       $243,060
Property Under Construction                                 --            --               --       263,505        204,740
Total Assets                                           311,447       350,173          398,351       448,674        460,382
Current Liabilities                                     59,433        57,669          104,772        37,251         36,309
Long-Term Obligations                                  205,883       133,804            6,052        59,879         56,703
Stockholders' Equity                                    46,131       158,700          287,527       351,544        367,370

</TABLE>

(1)      The Company has paid no dividends  on its Common Stock since  inception
         and  does  not  plan  to pay  dividends  on  its  Common  Stock  in the
         foreseeable future. In addition, the payment of dividends is subject to
         restrictions  described  in  Note 7 to  the  financial  statements  and
         discussed in Management's Discussion and Analysis.

                                      F-50



<PAGE>



 REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS





To American Mobile Satellite Corporation

We have audited in accordance with generally  accepted auditing  standards,  the
consolidated  financial statements of American Mobile Satellite  Corporation and
Subsidiaries (a Delaware corporation) included in this Form 10-K and have issued
our report thereon dated March 31, 1998. Our audits were made for the purpose of
forming an  opinion  on the basic  financial  statements  taken as a whole.  The
schedule listed in the index is the  responsibility of the Company's  management
and is  presented  for purposes of complying  with the  Securities  and Exchange
Commission's  rules  and is not  part of the  basic  financial  statements.  The
schedule has been subjected to the auditing  procedures applied in the audits of
the  basic  financial  statements  and,  in our  opinion,  fairly  states in all
material  respects  the  financial  data  required  to be set forth  therein  in
relation to the basic financial statements taken as a whole.




/s/ Arthur Andersen LLP
Washington, D.C.
March 31, 1998

                                      

<PAGE>


                                                                      SCHEDULE I

                      AMERICAN MOBILE SATELLITE CORPORATION

                  CONDENSED FINANCIAL INFORMATION OF REGISTRANT
                              (Parent Company Only)

                            Condensed Balance Sheets


<TABLE>
<CAPTION>


                                                                              December 31,
                                                                               1997              1996
                                                                        (in thousands of dollars)
ASSETS
<S>                                                                       <C>                  <C>     
Investment in and amounts due from  subsidiaries                          $  46,168            $158,713
                                                                          ---------            --------
Total assets                                                              $  46,168            $158,713
                                                                          =========            ========
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable and accrued expenses                                           $37                 $13
                                                                                ---                 ---
Stockholders' Equity
  Preferred Stock                                                                --                  --
  Common Stock                                                                  252                 251
  Additional paid-in capital                                                451,892             451,259
  Common stock purchase warrants                                             36,338              23,848
  Unamortized stock purchase warrants                                       (23,586)            (17,100)
  Accumulated loss                                                         (418,765)           (299,558)
                                                                           ---------           ---------
Total Stockholders' Equity                                                   46,131             158,700
                                                                             ------             -------
Total Liabilities and Stockholders' Equity                                $  46,168            $158,713
                                                                          =========            ========
</TABLE>

The  accompanying  notes  are an  integral  part  of  this  condensed  financial
information.

                                       S-1

<PAGE>


                                                                      SCHEDULE I

                      AMERICAN MOBILE SATELLITE CORPORATION

                  CONDENSED FINANCIAL INFORMATION OF REGISTRANT
                              (Parent Company Only)

                          Condensed Statements of Loss

<TABLE>
<CAPTION>

                                                                                      For the Years Ended December 31,
                                                                                 1997             1996                1995
                                                                                 ----             ----                ----
<S>                                                                         <C>              <C>                  <C>   
Management fees from wholly-owned subsidiary                                   $1,200           $1,200              $1,200
                                                                               ------           ------              ------
Operating Expenses
          Engineering operations                                                   --               --                  87
          Sales and marketing                                                      36               --                  91
          General and administrative                                            1,129            2,452                 595
                                                                                -----            -----                ----
          Total operating expenses                                              1,165            2,452                 773
                                                                                -----            -----                ----

Income (loss) from operations                                                      35           (1,252)                427
Interest income                                                                    --               --               3,258
Interest expenses                                                              (6,005)          (1,900)                 --
Equity loss in AMRC                                                            (1,301)              --                  --
                                                                             ---------        ---------          ---------
(Loss) income before net loss of Acquisition Company                           (7,271)          (3,152)              3,685
          Net loss of Acquisition Company - Note A                           (111,936)        (131,486)            (70,602)
                                                                             ---------        ---------            --------
Net Loss                                                                    $(119,207)       $(134,638)           $(66,917)
                                                                            ==========       ==========          ==========
</TABLE>

The  accompanying  notes  are an  integral  part  of  this  condensed  financial
information.


                                       S-2

<PAGE>


                                                                      SCHEDULE I

                      AMERICAN MOBILE SATELLITE CORPORATION

                  CONDENSED FINANCIAL INFORMATION OF REGISTRANT
                              (Parent Company Only)
<TABLE>

                       Condensed Statements of Cash Flows
<CAPTION>


                                                                             For the Years Ended December 31,
                                                                        1997             1996               1995
                                                                        ----             ----               ----
<S>                                                                   <C>              <C>                <C>   
Cash Provided from Operating Activities                               $   59            $1,424              $5,067
Investing Activities
         Advances to and investment in subsidiaries                     (343)           (2,672)           (162,778)
         Sales of short-term investments, net                             --                --              28,717
                                                                      ------           -------            --------
Cash (used in) investing activities                                     (343)           (2,672)           (134,061)
Financing Activities
         Proceeds from sale of Common Stock                              284             1,248               2,569
                                                                       -----             -----               -----

Cash Provided by Financing Activities                                    284             1,248               2,569
                                                                       -----             -----               -----
(Decrease) increase for the period                                        --                --            (126,425)
Beginning of period                                                       --                --             126,425
                                                                       -----             -----               -----        
End of period                                                         $   --           $    --            $     --
                                                                      ======           =======            ========


</TABLE>
The  accompanying  notes  are an  integral  part  of  this  condensed  financial
information.


                                       S-3

<PAGE>


                                                                      SCHEDULE I

                      AMERICAN MOBILE SATELLITE CORPORATION

                  CONDENSED FINANCIAL INFORMATION OF REGISTRANT
                              (Parent Company Only)

                     Notes to Condensed Financial Statements

The  condensed  financial  information  should be read in  conjunction  with the
consolidated financial statements.

Note A -- Background and Basis of Presentation

American Mobile Satellite Corporation (with its subsidiaries,  "American Mobile"
or the  "Company")  was  incorporated  on May 3, 1988,  by eight of the  initial
applicants for the mobile satellite services license,  following a determination
by the Federal Communications  Commission ("FCC") that the public interest would
be best served by granting the license to a consortium of all willing, qualified
applicants.  The FCC has authorized  American Mobile to construct,  launch,  and
operate a mobile satellite services system (the "Satellite Network ") to provide
a full range of mobile voice and data  services via  satellite to land,  air and
sea-based  customers  in a service area  consisting  of the  continental  United
States,  Alaska,  Hawaii,  Puerto Rico, the U.S.  Virgin Islands,  U.S.  coastal
waters,  international  waters and airspace and any foreign  territory where the
local  government  has  authorized  the  provision  of  service.  In March 1991,
American Mobile Satellite Corporation  transferred the mobile satellite services
license ("MSS license") to a wholly owned subsidiary, American Mobile Subsidiary
Corporation  ("AMSC  Subsidiary").  On April 7, 1995,  the Company  successfully
launched its first satellite ("MSAT-2"), from Cape Canaveral, Florida.

In late  1996,  the  Company  expanded  its mobile  data  business  through  the
acquisition  of  Rockwell  International  Corporation's  ("Rockwell")  dual mode
mobile  messaging and global  positioning and monitoring  service for commercial
trucking  fleets.  Rockwell was a private network  customer of the Company which
had purchased capacity from the Company on MSAT-2.

On December 31, 1997, the Company  entered into a Stock Purchase  Agreement (the
"Purchase Agreement") with Motorola, Inc. ("Motorola"), for the acquisition (the
"Acquisition") of ARDIS Company ("ARDIS"), a wholly-owned subsidiary of Motorola
that owns and operates a two-way wireless data communications  network.  Subject
to certain purchase price adjustment provisions,  the Company will acquire ARDIS
for a purchase  price of $50  million in cash and $50  million in the  Company's
Common Stock and  warrants  (the  "Purchase  Price").  The Company,  through the
acquisition  of ARDIS,  intends  to create a  nationwide  provider  of  wireless
communications services, including data, dispatch, and voice services, primarily
to business customers in the United States.

On October 16, 1997,  American Mobile Radio Corporation,  an indirect subsidiary
of American  Mobile through its subsidiary  AMRC Holdings,  Inc.  (together with
American Mobile Radio Corporation,  "AMRC"), was awarded a license by the FCC to
provide  satellite-based  Digital Audio Radio Service  ("DARS")  throughout  the
United States, following its successful $89.9 million bid at auction on April 2,


                                       S-4

<PAGE>


1997.  American  Mobile has entered  into an  agreement  with  WorldSpace,  Inc.
("WorldSpace"), by which WorldSpace has acquired a 20% participation in AMRC. In
connection  with the DARS  auction,  AMRC has also arranged for financing of the
FCC license fees as well as for initial working  capital needs,  which financing
has  included  the  issuance of options.  AMRC has and will  continue to receive
funding for this business from an independent source in exchange for debt and an
equity interest in AMRC. Accordingly, it is not expected that the development of
this business will have a material impact on the Company's  financial  position,
results of operations, or cash flows.

In the parent Company-only  financial  statements,  the Company's  investment in
subsidiaries  is  stated at cost less  losses of  subsidiaries.  The net loss of
subsidiaries is included in these financial  statements using the equity method.
The parent Company-only  statements exclude inter-company  interest. The Company
has entered into various transactions with its subsidiaries which are eliminated
in the December  31, 1997  audited  consolidated  financial  statements  and are
summarized as follows:

                                     1997              1996                1995
Investment in and amounts 
    due from subsidiaries          $46,167          $158,713            $287,527
Management fees                      1,200             1,200               1,200
Interest income                     29,520            29,485              23,445

Note B -- Investment in Subsidiaries

As stated in Note A, the Company  records its investment in  subsidiaries on the
equity  method.  In connection  with the  Acquisition,  the Company formed a new
wholly-owned subsidiary ("Acquisition Company") to hold the stock of all current
wholly-owned   operating   subsidiaries.   The   Acquisition   Company  has  six
wholly-owned subsidiaries. Additionally, the Company has an equity investment in
AMRC. The  recoverability  of such investment is subject to the risks associated
with expanding a developing business,  including successfully integrating ARDIS.
Specifically,  future operating results will be subject to significant business,
economic,    regulatory,    technical,   and   competitive   uncertainties   and
contingencies. Depending on their extent and timing, these factors, individually
or in the aggregate, could have an adverse effect on the Subsidiaries' financial
condition and future results of operations.

Adequate  liquidity  and capital are critical to the ability of the  Acquisition
Company  to  continue  as a going  concern  and to fund  subscriber  acquisition
programs  necessary  to reach  cash  positive  and  profitable  operations.  The
Acquisition  Company expects to continue to make significant capital outlays for
the  foreseeable  future to fund  interest  expense,  capital  expenditures  and
working capital prior to the time that it begins to generate  positive cash flow
from  operations and for the  foreseeable  future  thereafter.  The  Acquisition
Company  currently  believes  that  the net  proceeds  from the sale of the $335
million  in Notes and  warrants,  together  with the  borrowings  under the $200
million New Bank Financing,  the Motorola  financing,  and the proceeds from the
Satellite Lease  Agreement (all discussed  below) will be sufficient to meet the
Acquisition  Company's  currently  anticipated capital  expenditures,  operating
losses, working capital and debt service requirements through 1998 and beyond.


                                       S-5

<PAGE>


However,  if the Acquisition  Company's cash flows from operations are less than
projected,  the  Acquisition  Company  may not  meet its  financial  performance
agreements under the Guaranty Issuance Agreement and, if such conditions are not
met or waived, the Acquisition Company would not have access to additional funds
under the Revolving  Credit  Facility.  In addition,  even in the event that the
Acquisition  Company has access to such funds, it may require additional debt or
equity  financing in amounts  that could be  substantial.  The type,  timing and
terms of financing  selected by the  Acquisition  Company will be dependent upon
the  Acquisition  Company's  cash needs,  the  availability  of other  financing
sources and the prevailing conditions in the financial markets.  There can be no
assurance that any such sources will be available to the Acquisition  Company at
any given time or as to the favorableness of the terms on which such sources may
be available.

In connection  with the ARDIS  Acquisition,  the Company  raised $335 million in
cash proceeds from the private issuance of units ("Units")  consisting of 12 1/4
% Senior Notes ("Notes") due 2008 and one warrant to purchase 3.75749  shares of
Common Stock of the Company for each $1,000 principal amount of Notes. The Notes
are fully guaranteed by American Mobile Satellite Corporation. Additionally, the
existing Bank Financing was restructured. The New Bank Financing of $200 million
will consist of a $100 million  unsecured  five-year  reducing  Revolving Credit
Facility maturing March 31, 2003 and a $100 million five-year Term Loan Facility
with up to three additional one-year extensions subject to lender approval.  The
Revolving Credit Facility will be the obligation of Acquisition Company and will
rank pari passu with the Notes. The Term Loan Facility will be the obligation of
American Mobile Satellite Corporation and is secured by the stockholdings of the
Company,  principally its stockholdings in AMRC and the Acquisition Company, and
will be effectively subordinated to the Revolving Credit Facility and the Notes.
The New Bank Financing is severally guaranteed by Hughes Electronics Corporation
("Hughes"),  Singapore  Telecommunications  Ltd. ("Singapore Telecom") and Baron
Capital Partners, L.P. (the "Bank Facility Guarantors").  Additionally, Motorola
has agreed to provide  the Company  with up to $10  million of vendor  financing
(the "Vendor  Financing  Commitment"),  which will be available to finance up to
75% of the purchase  price of  additional  base  stations  needed to meet ARDIS'
buildout  requirements  under  certain  customer  contracts.  Loans  under  this
facility will bear interest at a rate equal to LIBOR plus 7.0%.  This commitment
is subject to customary conditions, including due diligence, and there can be no
assurance  that the facility  will be obtained by  Acquisition  Company on these
terms or at all.

On December 4, 1997, the Company and one of its wholly-owned  subsidiaries (AMSC
Subsidiary) entered into two simultaneous transactions.  The Company agreed with
TMI to acquire a one-half  ownership  interest in TMI's satellite,  MSAT-1, at a
cost of $60 million payable in equal  installments  over a five-year period (the
"Satellite  Purchase  Agreement");   certain  additional  payments  to  TMI  are
contemplated in the event that additional  benefits are realized by the Company.
Simultaneously,  the Company  entered into an agreement  (the  "Satellite  Lease
Agreement") with African Continental  Telecommunications Ltd. ("ACTEL"), for the
lease of MSAT-2,  for deployment over  sub-Saharan  Africa.  The five-year lease
provides for  aggregate  lease  payments to the Company of $182.5  million.  The
lease includes a renewal  option  through the end of the life of MSAT-2,  on the
same lease terms, at ACTEL's  election  exercisable 2 1/2 years prior to the end
of the initial lease term.  Closing under the Satellite  Purchase  Agreement and
Satellite  Lease  Agreement  is  subject  to  a  number  of  conditions.  It  is
anticipated   that  the  closing  under  both  leasing   agreements  will  occur
simultaneously in the spring of 1998.

                                       S-6

<PAGE>


Note C -- Guarantee

The Company has guaranteed  various  obligations of Acquisition  Company.  These
guaranteed  obligations  include amounts  borrowed under the New Bank Financing,
ground segment financing  agreements and obligations of Acquisition  Company and
its subsidiaries  under an office lease agreement and various capital  equipment
leases.


Note D -- Legal Matters

In 1992, a former director of American Mobile filed an Amended Complaint against
the Company alleging  violations of the  Communications Act of 1934, as amended,
and of the Sherman Act and breach of  contract.  The suit seeks  damages for not
less than $100 million  trebled under the antitrust laws plus punitive  damages,
interest,  attorneys fees and costs. In mid-1992, the Company filed its response
denying all  allegations.  The Company's motion for summary  judgment,  filed on
March  31,  1994,  was  denied  on April 18,  1996.  The  trial in this  matter,
previously  set for December 1997, has been postponed to a date to be determined
in 1998.  Management  believes that the ultimate outcome of this matter will not
be material to the Company's financial  position,  results of operations or cash
flows.



                                       S-7

<PAGE>






                                                                 Exhibit 10.3c
                                                                 ---------------

                                                          Revised by Amendment 7


                                 AMENDMENT NO.7
                               TO THE AMSC/HUGHES
                            MSAT SPACECRAFT CONTRACT


This Amendment No. 7 to the MSAT Spacecraft AMSC-S/C-11/90-001 dated 10 December
1990 (the  Contract) as amended,  is made effective this  2nd  day  of  December
1997 by and between:

AMSC  SUBSIDIARY   CORPORATION,   as  assignee  of  AMERICAN  MOBILE   SATELLITE
CORPORATION,  (hereinafter  referred to as "AMSC"), a company incorporated under
the laws of the State of Delaware, having its principle place of business in the
Reston, Virginia, U.S.A.

AND

HUGHES  SPACE  AND   COMMUNICATIONS   COMPANY,   (hereinafter   referred  to  as
"Contractor"  or "HUGHES"),  a company  organized and existing under the laws of
Delaware with its principal place of business located in El Segundo, California,
USA.

WHEREAS, AMSC and HUGHES have heretofore entered into the Contract for provision
of a satellite and other items therein; and,

WHEREAS,  AMSC has  decided it will  lease the M2  Spacecraft  ("Spacecraft"  or
"Satellite")  to   African  Continental   Telcommunications   Ltd.  (hereinafter
referred to as "ACTEL" or "Lessee"); and,

WHEREAS,  pursuant to AMSC's request, HUGHES will enter into a separate contract
with Telesat Canada  (hereinafter  referred to as "Telesat" or "Operator"),  for
software and  procedures  so that Telesat,  as AMSC's  satellite  operator,  can
invert and roll the Spacecraft, and,

WHEREAS,  AMSC and  HUGHES  have  agreed to amend the terms of the  Contract  to
reflect  the  impact of AMSC's  lease of the  Satellite  with  ACTEL and  HUGHES
entering into a separate contract with Telesat; and

WHEREAS,  AMSC and HUGHES had previously  agreed to modify the Contract with the
approval  of a  revised  MSAT IRD with  Atlas  and  certain  Engineering  Change
Requests  (ECRs),  and the  Parties  now  wish to  incorporate  this IRD and the
following  ECRs  as  an  administrative   matter:  ECRs  456346-58,   456415-65,
456348-75,  456349-76,  456350-77,  456351-97,  456352-98A, into the Common Test
Plan;  and TMI has approved the same ECRs to change the MSAT IRD with Atlas into
their  Assignment  Agreement  and to make the same  related  adjustments  in the
Common  Technical  Specification  and Common  Test Plan of the  TMI/SPAR//HUGHES
Assignment Agreement; and

NOW,  THEREFORE,  in  consideration  of the mutual  benefit to be  derived,  the
Parties hereto agree that the Contract is amended as follows:

         Revise the Contract terms and conditions by  substituting  the attached
pages  dated  November  1997 for the  existing  pages  and  adding  new pages as
follows:

         4, 20, 20A, 39A, 74A, 74B, 74C

         Revise the  Attachment  2  Technical  Specification  for  Satellite  by
substituting  the attached pages attached October 1995 for the existing pages as
follows:

         Appendix A, pages 9 and 13

<PAGE>
         Revise the  Attachment 4 Test Plan by  substituting  the attached pages
dated October 1995 for the existing pages and adding new pages as follows:

         2-4, 2-5, 4-6, 4-7, 4-7A, 4-8, 5-5, 5-6
         A-3, A-11A,  A-11B,  A-11C, A-14, A-15, A-17A,  A-17B, A-20, A-20A C-1,
         C-33, C-34, C-35, C-36, C-37, C-45, C-49

For purposes of clarity and  traceability,  each of the  substitute  pages above
(except for the Payment  Plan,) have been annotated to reflect the deleted text,
shown with a "strike  through"  () and/or  change  bar in the right hand  margin
(example |); and, the new text, shown by underling (example), italics (example),
a different  font (example  example)  and/or by a change bar in the right margin
(example  |). Each page is also  designated  with  "Revised  Amendment 7" in the
upper right hand corner.

There is no modification to this Contract except as expressly set forth above.




<PAGE>

                                                          Revised by Amendment 7


IN WITNESS WHEREOF, the Parties hereto have executed this Amendment No. 7 to the
MSAT Contract AMSC-S/C-11/90-001.


AMSC SUBSIDIARY CORPORATION                     HUGHES SPACE &
                                                COMMUNICATIONS COMPANY

By: /s/Randy Segal                              By:  /s/Patrice Gray Mitchell
    --------------                                   ------------------------
       (Signed)                                       (Signed)

    Randy Segal                                      Patrice Gray Mitchell
    -----------                                      ---------------------
    (Printed or Typed)                               (Printed or Typed)


Title: Vice President                            Title:  Manager, Commercial/
                                                        International Contracts






<PAGE>


                                                          Revised by Amendment 7












                         TERMS AND CONDITIONS REVISIONS


                                 AMENDMENT NO. 7

                                       To

                            AMSC/HUGHES MSAT CONTRACT


                                  NOVEMBER 1997





<PAGE>


                                                          Revised by Amendment 7


and made a part of this Contract.

     "Contract  Price" means the total amount  expressed in this  Contract to be
payable to the Contractor  for the  satisfactory  performance of the Work,  such
Contract  Price  to  include,   where  applicable,   all  charges  for  Worker's
Compensation  insurance,  charges for  insurance,  shipping  costs and all other
assessments, except only as specifically excluded in Article 4.0.

     "Day"  means a  continuous  24-hour  period  commencing  a  12:00  midnight
(Greenwich Mean Time).

     "Designated  Launch Site" means the launch facility  provided by the Launch
Agency.

     "Equipment"  means  individual  assemblies,   parts  thereof  and  complete
systems.

     "Financing Entity" means an institution or other entity which lends
money or otherwise  provides  financing to AMSC for payment of amounts due under
this Contract.

     "Intentional  Ignition" means the deliberate,  intentional  ignition of the
first stage of any launch  vehicle for the purpose of launching  the  Spacecraft
into orbit.

     "Launch Agency" means the  organization  selected by AMSC to perform launch
services, including furnishing the launch vehicle, launch support, Equipment and
facilities for the purpose of launching the Spacecraft into orbit.

     "Properly  Operated  Satellite"  means a Satellite which is being monitored
and  commanded  in  accordance  with the  written  directives  and  instructions
furnished  to  AMSC  by  Contractor  in  the  Recommended   Satellite  Operating
Procedures  and any formal  amendments  thereto under this Contract or under the
Software Development and License Contract between Hughes and Telesat.







<PAGE>


                                                          Revised by Amendment 7


               Performance  Incentive  Payments  commensurate  with the  profits
               generated by the Spacecraft.

               Impact to Incentives due to the Inversion of the Satellite



               AMSC shall have Telesat  perform the  relocation and inversion of
               the  Satellite.  Telesat  shall then operate the  Satellite in an
               inverted  position.  If the Satellite  fails during the inversion
               and/or  relocation   procedures  or  within  six  (6)  months  of
               completion  of the inversion and  relocation  procedure  provided
               that the  Satellite  is  exposed  to both the  Summer  and Winter
               solstices ("the Period"),  Hughes shall be entitled to payment of
               the PIPs, plus interest for each regularly  scheduled period from
               May  1995  through  the  3650th  day  thereafter.  If there is an
               anomaly  during  this  Period,  it shall be  deemed  to have been
               caused  by  the  Spacecraft  inversion  and  there  shall  be  no
               reduction  in the  PIPs  to be  paid  over  the  lifetime  of the
               Satellite,  unless AMSC to can prove to Hughes' satisfaction that
               it was not caused by the  inversion.  The issue of whether Hughes
               is satisfied with AMSC's claim shall not be subject to dispute or
               arbitration.  If there is an anomaly on the  Satellite  after the
               Period,  the  basic  contract  provisions  shall  apply  and this
               Paragraph 7.1(3) shall no longer be applicable.


               Extended  Life  Incentives.  Following  the  THREE  THOUSAND  SIX
               HUNDRED  AND  FIFTY  (3,650)  day  period in  7.1(2)  above,  the
               Contractor shall receive Extended Life Incentive  Payments of TWO
               THOUSAND  AND  SEVENTY-FIVE  U.S.  DOLLARS   (US$2,075.00)   plus
               interest per day,  plus SEVEN HUNDRED AND  NINETY-SEVEN  CANADIAN
               DOLLARS   (C$797.00)  plus  interest  per  day,  subject  to  the
               reductions in accordance with Paragraphs 7.1(2)(c) and 7.1(2)(d).
               -------------------------

     7.2 All  Performance  Incentive  Payments  made  pursuant  to this  Article
includes  interest  accrued  from the time that the  Spacecraft  begins  earning
Performance  Incentives.  An Interest  Accrual  Factor (IAF) shall be applied to
each payment in accordance with the following formula.

                  (APRn + 1.0) x 60
         Fn =                               + 1
              ---------------------------------

                            365


     16.6  LIMITATION OF LIABILITY FOR HUGHES' WORK ON THE SPACECRAFT  INVERSION
HUGHES  MAKES NO  WARRANTY,  EXPRESS OR IMPLIED,  TO AMSC,  TELESAT OR ANY OTHER
PERSON OR ENTITY  CONCERNING  THE  SPACECRAFT  INVERSION  AND  RELOCATION OR THE
PERFORMANCE OF THE SATELLITE. AMSC SHALL INDEMNIFY AND HOLD HARMLESS HUGHES FROM
AND AGAINST ANY LOSS, DAMAGE,  LIABILITY OR EXPENSE  (INCLUDING  ATTORNEY'S FEES
AND OTHER EXPENSES OF INVESTIGATING OR DEFENDING  CLAIMS) RESULTING FROM (I) ANY
REPRESENTATION  MADE BY AMSC TO ANY THIRD PARTY  RELATING TO THIS WORK; AND (II)
ANY   CLAIMS    MADE   BY   ANY   THIRD    PARTY    RELATING   TO   THIS   WORK.
- -------------------------------------------------------------------------------







<PAGE>


                                                          Revised by Amendment 7


ARTICLE 42: OTHER  CONDITIONS  RELATING TO THE  INVERSION  AND  OPERATION OF THE
SATELLITE

     42.1 Export Licenses

     AMSC shall  obtain all  necessary  USG export  licenses  for the  Satellite
and/or  technical  data prior to leasing the Satellite to ACTEL and  authorizing
Telesat to operate the  Satellite.  Upon  AMSC's  request,  HUGHES will  provide
limited assistance to AMSC in processing such license applications.


     42.1 Transfer of Hughes' Proprietary Information

     (a) AMSC  agrees  that the Lessee and the  Operator  ("Receiving  Parties")
     shall enter into a written agreement with AMSC ("Agreement") to protect any
     Hughes  Proprietary  Information  ("Proprietary   Information")  which  was
     provided  under  this  Contract  and which AMSC  provides  to the Lessee or
     Operator.  The Receiving  Parties  shall keep  Proprietary  Information  in
     confidence and not disclose to any person or entity, any of the Proprietary
     Information,  except as otherwise  provided  below.  This  Agreement  shall
     require  that the  Receiving  Parties  exercise  the same degree of care to
     guard  against   unauthorized   disclosure  or  use  of  such   Proprietary
     Information  as  Receiving   Parties  employ  with  respect  to  their  own
     Proprietary  Information of like importance,  but in no event,  less than a
     reasonable  degree of care.  This  Agreement  shall also  require  that the
     Receiving Parties make the Proprietary  Information available only to those
     of their employees or agents having a "need to know" in order to operate or
     maintain the Satellite; and further, that each of their employees or agents
     shall be  advised  that  they are  obligated  to  protect  the  Proprietary
     Information in a manner consistent with the Agreement.







<PAGE>


                                                          Revised by Amendment 7


     The  Receiving  Parties  shall not be liable for the  disclosure  or use of
Proprietary Information if the same is:

     in or enters the public domain, other than by breach of this Agreement;

     known to the Receiving Parties at the time of first receipt,  or thereafter
becomes known to the  Receiving  Parties  without  similar  restrictions  from a
source other than Hughes, as evidenced by written records;

     developed by the Receiving Parties independent of any disclosure  hereunder
as evidenced by written records.

In the event  AMSC,  the Lessee or Operator  of the  Satellite  is acquired by a
competitor of Hughes,  the Parties agree that Hughes would be irreparably harmed
if any  competitor  of  Hughes,  as  determined  by  Hughes  in  its  reasonable
discretion,  were  to  acquire  access  to  any of  the  intellectual  property,
Proprietary  Information or other technology,  data or inventions  covered under
the Contract (collectively, the "Intellectual Property"),  regardless of whether
such  competitor  has an  ownership  interest in AMSC,  the Lessee or  Operator.
Accordingly,  the  Parties  agree that no  competitor  of Hughes  shall be given
access to any of the Intellectual  Property, and that should a competitor obtain
control of AMSC,  the Lessee or the  Operator  or  otherwise  be an  assignee or
transferee  of AMSC,  the  Lessee or the  Operator,  Hughes may take any and all
reasonable   steps  to  safeguard   and  protect  its   Intellectual   Property.
Notwithstanding  any  provisions  of the  Contract  requiring  arbitration,  the
foregoing  agreement may be enforced by Hughes by entry of injunctive relief, in
addition  to  all  other  remedies  available  to  Hughes  under  the  Contract,
applicable law or otherwise.







<PAGE>


                                                          Revised by Amendment 7


     42.2 A condition  precedent to the  effectiveness of this Amendment 7 shall
be a binding agreement between AMSC and ACTEL for the lease of the Satellite and
a binding agreement  between AMSC and Telesat for the inversion,  relocation and
operation of the Satellite.







<PAGE>





                                                                  Exhibit 10.13c
                                                                  --------------
EXECUTIVE:

AWARD NO. 1998 -

DATE OF GRANT:

NUMBER OF SHARES:


                      AMERICAN MOBILE SATELLITE CORPORATION
                             1989 STOCK OPTION PLAN


                                      * * *

                           RESTRICTED STOCK AGREEMENT


     1. Definitions.  In this Agreement,  terms with initial capitals shall have
        -----------
the meanings provided in the Plan, except as follows:

     "Agreement" means this Restricted Stock Agreement.

     "Awarded  Shares" means the shares of Common Stock awarded to the Executive
pursuant to Section 2 hereof

     A "Change of Control" means the occurrence of any of the following  events:
any Person or Persons acting together,  excluding  employee benefit plans of the
Corporation, are or become the "beneficial owner" (as defined in Rules 13d-3 and
13d-5 under the Exchange Act or any successor  provisions  thereto except that a
Person  that has the right to acquire  securities  of the  Corporation  shall be
deemed to be the "beneficial owner" of such securities whether or not such right
is  immediately  exercisable),  directly or  indirectly,  of  securities  of the
Corporation  representing  forty  percent  (40%) or more of the combined  voting
power of the  Corporation's  then  outstanding  securities  determined as if all
rights of such Person or Persons to acquire such  securities  had been exercised
immediately  prior to such  determination  whether  or not such  rights are then
immediately exercisable;

     the Corporation's shareholders approve (or, in the event no approval of the
Corporation's  shareholders is required, the Corporation  consummates) a merger,
consolidation,  share exchange,  division or other reorganization or transaction
of the Corporation (a  "Fundamental  Transaction")  with any other  corporation,
other than a Fundamental Transaction which would result in the voting securities
of the Corporation outstanding immediately prior thereto continuing to represent
(either by remaining outstanding or by being converted into voting securities of
the surviving entity) at least eighty percent (80%) of the combined voting power
immediately  after  such  Fundamental   Transaction  of  (I)  the  Corporation's
outstanding securities,  (ii) the surviving entity's outstanding securities,  or
(iii) in the case of a  division,  the  outstanding  securities  of each  entity
resulting from the division, in each case determined as if all rights to acquire
such  securities had been  exercised  immediately  prior to such  determination,
whether or not such rights are then immediately exercisable;

     the shareholders of the Corporation approve a plan of complete  liquidation
or winding-up of the Corporation or an agreement for the sale or disposition (in
one transaction or a series of transactions) of all or substantially  all of the
Corporation's assets; or

     during any period of twenty-four consecutive months, individuals who at the
beginning of such period  constituted the Board  (including for this purpose any
new director  whose  election or  nomination  for election by the  Corporation's
shareholders  was  approved  by a  vote  of at  least  two-thirds  (2/3)  of the
directors  then  still in office who were  directors  at the  beginning  of such
period) cease for any reason to constitute at least a majority of the Board.

     "Date of Expiration" means, subject to the provisions of Section 3 of
this Agreement, ten (10) years after the Date of Grant.

     "Date of  Grant"  means the date set forth as the "Date of Grant" on page 1
of this Agreement.

     "Disability" means permanent and total disability of the Executive.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     "Executive"  means the person  identified as the  "Executive"  on page 1 of
this Agreement.

     "Involuntary  Termination"  means  termination  by  the  Corporation  or  a
Subsidiary of the  Executive's  employment  with the Corporation or a Subsidiary
or, in connection with or following a Change of Control, a substantial reduction
by the  Corporation  or  Subsidiary  in the salary,  benefits or position of the
Executive, but does not include any such termination or substantial reduction as
a result of Termination for Good Cause.

     "Person" shall have the meaning given in Section 3(a)(9) of the
Exchange  Act and shall  also  include  any  syndicate  or group  deemed to be a
"person" under Section 13(d)(3) of the Exchange Act.

     "Plan" means the American Mobile  Satellite  Corporation  1989 Stock Option
Plan.

     "Restriction  Period"  means the period  beginning on the Date of Award and
ending  on (i) the  first  anniversary  of the Date of Grant,  with  respect  to
33-1/3% of the Awarded  Shares  (rounded to the nearest whole number of shares),
(ii) the second  anniversary of the Date of Grant, with respect to an additional
33-1/3% of the Awarded  Shares  (rounded to the nearest whole number of shares),
and (iii) the  third  anniversary  of the Date of  Grant,  with  respect  to the
remaining Awarded Shares;  provided,  however, that unless the Committee, in its
sole  discretion,   determines  otherwise,  the  Restriction  Period  shall  not
terminate  with respect to any Awarded Shares prior to the earlier of either (A)
the date  that the  "Start  Date"  shall  have  occurred  under the terms of the
Corporation's    Satellite    Lease    Agreement   with   African    Continental
Telecommunications,  Ltd.  ("ACTEL"),  dated as of  December  2, 1997 or (B) the
first  date  after the date  hereof on which the  Corporation  becomes  earnings
before interest,  taxes,  depreciation and amortization  (EBITDA)  "break-even."
Notwithstanding   the  foregoing,   the  Restriction  Period  shall  immediately
terminate  with  respect to all Awarded  Shares in the event of [the Executive's
Involuntary  Termination in connection  with, or within two years  following,]*
a Change of Control.

          *Bracketed language omitted in Chief Executive Officer Agreement.

     "Termination  for  Good  Cause"  means  termination  as  a  result  of  the
commission of a felony by the Executive.

     2.  Award of  Restricted  Shares.  The  Corporation  hereby  awards  to the
        -- --------------------------
Executive a total of        shares of Common Stock ("Awarded  Shares")  pursuant
                     ------
to  Section 9 of the Plan.  During  the  Restriction  Period,  each  certificate
representing Awarded Shares shall be held by the Corporation or its designee and
shall contain the following legend:

     "This certificate and the shares of stock represented hereby are subject to
the terms and conditions  (including  the risks of forfeiture  and  restrictions
against  transfer)  contained in the American Mobile Satellite  Corporation 1989
Stock Option Plan and an Agreement entered into between the registered owner and
American Mobile  Satellite  Corporation.  Release from such terms and conditions
shall  be made  only in  accordance  with  the  provisions  of the  Plan and the
Agreement,  a copy of each of which is on file in the office of the Secretary of
American Mobile Satellite Corporation."

     3. Terms,  Conditions and Restrictions.  Awarded Shares shall be subject to
        -----------------------------------
the terms,  conditions and  restrictions  contained in the Plan, are as follows:


     Prohibitions  Against Sale,  Assignment,  etc. Awarded Shares, the right to
     ----------------------------------------------
vote Awarded Shares and the right to receive  dividends thereon may not be sold,
assigned, transferred,  exchanged, pledged, hypothecated or otherwise encumbered
during the  Restriction  Period with  respect to such Awarded  Shares  except as
provided in the Plan. 

     Forfeiture.  In the  event of either  (a) the  Executive's  termination  of
     ----------
employment  with the  Corporation  prior to the lapse of the  Restricted  Period
other than by reason of death or  Disability  of the  Executive or in connection
with, or within two years  following,  a Change of Control or (b) the occurrence
of the Date of  Expiration  prior to the lapse of the  Restriction  Period  with
respect to particular Awarded Shares,  such Awarded Shares shall be forfeited by
the Executive to the  Corporation  and neither the Executive nor any successors,
heirs,  assigns or personal  representatives  of the Executive shall  thereafter
have any further rights or interest in such Awarded  Shares or the  certificates
representing such Awarded Shares.

     Termination  of  Restrictions.  In the event the  Restriction  Period shall
     -----------------------------
terminate  with respect to  particular  Awarded  Shares and such Awarded  Shares
shall  not  theretofore  have  been  forfeited  to  the  Corporation,  then  the
Corporation  shall  reissue the  certificate  representing  such Awarded  Shares
without the legend  referred to in Section 2 of this Agreement and shall deliver
such  certificate   to   the   Executive   or   his   legal    representative.


     Effect of Death or Disability.  If the Executive's employment is terminated
     -----------------------------
during the Restriction  Period due to death or Disability,  the Executive shall,
as of the date of such death or Disability,  be deemed to have remained employed
by the Corporation until the third anniversary of the Date of Grant for purposes
of Section 1(l) hereto. 

     Withholding. The Corporation's obligation to deliver shares of Common Stock
     -----------
upon the  termination  of the  Restriction  Period  with  respect to any Awarded
Shares shall be subject to the  satisfaction  of applicable  federal,  state and
local  tax  withholding  requirements.   The  Executive  may  satisfy  any  such
withholding  tax obligation by either of the following means or by a combination
of such means: (a) tendering a cash payment;  or (b) authorizing the Corporation
to withhold shares of Common Stock from the reissued shares  otherwise  issuable
to the Executive as the result of the termination of the Restriction Period with
respect to any Awarded  Shares.  For  purposes of this Section  3(e),  shares of
Common Stock that are withheld to satisfy applicable  withholding taxes shall be
valued at their Fair Market Value.

     4.  Rights as  Stockholder.  Except as  provided  in Section 3 hereof,  the
         ----------------------
Executive shall have all the rights and privileges of a stockholder with respect
to the  Awarded  Shares,  including  (but not  limited to) the right to vote the
Awarded  Shares  and the  right  to  receive  dividends.  All  such  rights  and
privileges    shall   cease   upon    forfeiture   of   the   Awarded    Shares.


     5. Subject to the Plan.  The Awarded  Shares and this Agreement are subject
        -------------------
to the  terms and  conditions  of the Plan,  which  are  incorporated  herein by
reference  and  made a part  hereof,  but the  terms of the  Plan  shall  not be
considered an enlargement of any benefits under this Agreement. In addition, the
Awarded  Shares and this  Agreement  are  subject  to any rules and  regulations
promulgated  by the Committee in accordance  with its authority  under the Plan.


     6. Employment.  Neither the grant or issuance of Awarded Shares pursuant to
        ----------
this Agreement nor any term or provision of this Agreement  shall  constitute or
be  evidence  of any  understanding,  express  or  implied,  on the  part of the
Corporation or any Subsidiary to employ the Executive for any period. 


<PAGE>


         IN WITNESS  WHEREOF,  the  Corporation  has caused this Agreement to be
signed on its behalf effective as of the Date of Grant.

ATTEST:                                    AMERICAN MOBILE
                                           SATELLITE CORPORATION



                                           By:
                                              ---------------------------



                                              ---------------------------
                                                       EXECUTIVE




<PAGE>





                        FIFTH AMENDMENT TO TERM AGREEMENT


         THIS FIFTH AMENDMENT TO TERM LOAN AGREEMENT  ("Amendment")  dated as of
December  19th,  1997, by and between AMSC  SUBSIDIARY  CORPORATION,  a Delaware
corporation  ("Borrower"),  with offices at 10802 Parkridge  Boulevard,  Reston,
Virginia 22091, and NTFC CAPITAL CORPORATION,  a Delaware corporation  (formerly
known as Northern Telecom Finance Corporation)  ("Lender"),  with offices at 220
Athens Way, Nashville, Tennessee 37228.

                                   BACKGROUND

         A. Borrower and Lender  executed that certain Term Loan Agreement dated
as of May 28, 1993,  as amended by the First  Amendment  to Term Loan  Agreement
dated as of April 8, 1994, the Second  Amendment to Term Loan Agreement dated as
of August  1,  1995,  the Third  Amendment  to Term Loan  Agreement  dated as of
November  7,  1995 and a Fourth  Amendment  dated as of  October  1, 1996 (as so
amended,  the "Original Loan Agreement")  providing for certain loans to be made
to Borrower by Lender (the  "Loans").  The Loans are  represented by the Amended
and Restated Equipment Note dated as of October 1, 1996,  amending and restating
the Note  originally  dated as of May 28,  1993 and as  previously  amended  and
restated as of April 8, 1994 (as so amended, the "Original Note").

         B. Borrower has requested Lender to make certain changes in the payment
schedule,  and  Lender  is  willing  to make  such  changes,  on the  terms  and
conditions set forth herein.

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable   consideration,   the  receipt  and   adequacy  of  which  are  hereby
acknowledged, the parties hereto agree as follows:

         1.  Definitions:  All  capitalized  terms  used  herein  which  are not
otherwise  defined  shall have the meanings  given to such terms in the Original
Loan Agreement, as amended hereby.

         2.  Amendment  to  Section  1.01.  Section  1.01 of the  Original  Loan
Agreement is hereby  amended by amending  each of the following  definitions  to
read in its entirety as follows:

                           "Interest  Payment Date":  the First Interest Payment
                  date  for the  Loan  and (a) the  first  Business  Day of each
                  calendar month  thereafter  until  September 30, 1996, (b) the
                  first day of each Interest Period from October 1, 1996 through
                  October 1, 1997, and (c) December 31, 1997 and (d) February 1,
                  1998, March 1, 1998 and April 1, 1998.

                           "Interest  Rate":  a variable  interest rate equal to
                  (a) LIBOR plus 4.5% through and including  September 30, 1996,
                  (b) LIBOR plus 2.5% form and after  October  1, 1996,  and (c)
                  LIBOR plus 4.5% from and after December 31, 1997, in each case
                  adjusted on the first day of each Interest Period.

<PAGE>
                           "Maturity  Date":  April 1, 1998, on which principal,
                  interest, premium, expenses, fees, penalties and other amounts
                  due under the Note shall be finally due and payable.

         3.  Amendment  to  Section  2.05.  Section  2.05 of the  Original  Loan
Agreement is hereby amended to read in its entirety as follows:

                           2.05.  Principal  Payments.  Borrower  shall make the
                  principal  payment  in  the  amount  of  One  Million  Dollars
                  ($1,000,000)  on December  31,  1997.  Thereafter,  the entire
                  outstanding  principal  amount of the Note and all accrued but
                  unpaid interest and all other unpaid amounts due thereunder
                  shall be paid on the Maturity Date.

         4. Amended and Restated Note.  Contemporaneously  with the execution of
this  Amendment,  Borrower  shall  execute  an  Amended  and  Restated  Note  to
incorporate the terms hereof, in form and substance satisfactory to Lender.

         5. Representations and Warranties of Borrower.  The Borrower represents
and  warrants to Lender that the  Borrower  has not  executed any other deeds of
trust,  mortgages,  security agreements or financing  statements in favor of any
other person or entity  affecting the  Collateral;  that no person or entity has
any rights to claim a lien upon the  Collateral  superior to the lien of Lender;
that no  Default  or Event of  Default  has  occurred  under the  Original  Loan
Agreement  (except  Defaults and Events of Default that are waived herein);  and
that no event has occurred and no claim,  offset or other condition exists which
would  relieve  the  Borrower  of any of its  obligations  to  Lender  under the
Original  Loan  Agreement  or  other  documents  executed  by  the  Borrower  in
connection therewith.

         6. Lender's Fees and Expenses. Borrower shall pay to Lender, on demand,
all costs and expenses,  including  reasonable legal fees, incurred by Lender in
connection with the preparation,  negotiation,  execution or  implementation  of
this Amendment.

         7. Full Force and Effect.  Except as specifically  modified herein, the
Original Loan Agreement shall continue in full force and effect as written,  and
nothing  herein is  intended  to, nor shall it,  release,  diminish or waive the
rights of the parties under the Original Loan Agreement,  the Note or other Loan
Documents.

         8. Possible Extension. Borrower has represented to Lender that Borrower
expects to complete  certain  financing by March 31, 1998. If such  financing is
not  completed  by  that  date,   but  Borrower  can   demonstrate  to  Lender's
satisfaction  that significant  progress (as determined by Lender) has been made
towards such  completion and that such financing is scheduled and anticipated to
be  completed  in the  immediate  future,  and if no other  Default  or Event of
Default has then  occurred,  Lender will consider  extending the maturity due to
not later than May 1, 1998,  subject to the execution of such  documentation  as
Lender may deem  necessary  to implement or evidence  such  extension.  Lender's
agreement to consider  extending the maturity date is not a commitment to do so,
and Lender shall make any such decision in its sole and absolute discretion.


<PAGE>



         9.  Counterparts.  This  Amendment  may be  executed  in any  number of
counterparts  (by  facsimile  transmission  or  otherwise)  and by the different
parties hereto on separate counterparts,  each of which, when so executed, shall
be deemed an original,  but all such  counterparts  shall constitute but one and
the same instrument.

         IN WITNESS WHEREOF, this Fifth Amendment to the Term Loan Agreement has
been  executed  as of the day first  above  written by the  parties'  authorized
representatives.

LENDER:                                       BORROWER:

NTFC CAPITAL CORPORATION                      AMSC SUBSIDIARY CORPORATION



By: /s/Henry Craig                            By: /s/Richard J. Burnheimer
    --------------                                 ------------------------

Title: VP-Chief Credit Officer                Title: Vice President & Treasurer
       -------------------------                     --------------------------

<PAGE>



                            AMENDED AND RESTATED NOTE


$5,933,095.61                               Originally dated as of: May 28, 1993
                            Previously Amended and Restated as of: April 8, 1994
                                      Amended and Restated as of October 1, 1996
                                    Amended and Restated as of December 19, 1997


         FOR VALUE RECEIVED, AMSC SUBSIDIARY CORPORATION ("Borrower"),  promises
to pay to the order of NORTHERN  TELECOM FINANCE  CORPORATION  (the "Lender") at
its offices located at 220 Athens Way, Nashville,  Tennessee,  37228, or to such
other Person and such other location  specified in writing by the holder hereof,
in lawful  money of the United  States of America an din  immediately  available
funds the principal  amount of Five Million Nine Hundred  Thirty-Three  Thousand
Ninety Five Dollars and Sixty-One Cents ($5,933,095.61),  together with interest
thereon and other  amounts due as provided  below.  Notations  on the  Schedules
attached hereto are for convenience  only, and the failure of the Lender to make
any notation on any  Schedule,  or any  incorrect  notation by the Lender on any
Schedule,  shall not diminish the  obligations  of the Borrower under this Note.
This Note shall mature on April 1, 1998 (the "Maturity Date").

         The "Initial Payment Date" means the first Business Day of the calendar
month following the month in which the Termination  Date falls. The "Termination
Date" means the earliest of the  following  three dates:  (a) December 31, 1994,
but  only if  Final  Acceptance  (as  defined  in the  Loan  Agreement)  ("Final
Acceptance")  has  occurred on or before  such date;  or (b) the last day of the
month  of the  date of Final  Acceptance  occurs  between  January  1,  1995 and
February 28, 1995; and (c) March 31, 1995.

         This Note has been made and  delivered  pursuant to that  certain  Term
Loan  Agreement  dated as of May 28, 1993 by and between  the  Borrower  and the
Lender,  as amended by the First  Amendment to Term Loan  Agreement  dated as of
August 1, 1995, the Third  Amendment to Term Loan Agreement dated as of November
7, 1995, the Fourth  Amendment to Term Loan Agreement  dated October 1, 1996 and
the Fifth  Amendment to Term Loan  Agreement of even date  herewith (as the same
may  be  modified,  amended  or  supplemented  from  time  to  time,  the  "Loan
Agreement") and is the Note described in Section 2.03(a)  thereof.  Any term not
otherwise defined in this Note shall have the meaning ascribed to it in the Loan
Agreement.  Reference  is made to the Loan  Agreement,  which among other things
provides for the  acceleration  of the maturity  hereof upon the  occurrence  of
certain  events and for  prepayments in certain  circumstances  and upon certain
terms and  conditions.  This Note is secured by the Collateral  described in the
Security Documents.

         All advances  hereunder  shall bear  interest at the Interest  Rate (as
defined  below)  from the date of such  Advance  until  such  amount  is due and
payable (whether on any Payment Date, at the Maturity Date, by acceleration,  or
otherwise).

         The  "Interest  Rate"  shall be a variable  interest  rate equal to (a)
LIBOR plus 4.5% through and  including  September  30, 1996,  and (b) LIBOR plus
2.5% from and after October 1, 1996,  through and  including  December 31, 1997,
and (c) LIBOR plus 4.5%  thereafter,  in each case  adjusted on the first day of
each Interest Period.


<PAGE>




         "LIBOR":  in respect of any Interest  Period,  the rate of interest per
annum  shall be the rate quoted in the "money  rates"  column of The Wall Street
Journal for the three-month LIBOR (London Interbank Offered Rates). This rate is
to be  determined  on the second  Business Day before the  commencement  of such
Interest  Period (each such second  Business Day before the  commencement  of an
Interest  Period being  hereinafter  referred to as an  "Interest  Determination
Date").

         "Interest  Period":  each three (3)  calendar  month  period  beginning
January 1, April 1, July 1 and October 1 of each calendar year provided that:

         (A) if any Interest Period  pertaining to a Loan would otherwise end on
a day which is not a Business Day, that Interest Period shall be extended to the
next  succeeding  Business Day unless the result of such  extension  would be to
carry such  Interest  Period into another  calendar  month,  in which event such
Interest Period shall end on the immediately preceding Business Day;

         (B) any Interest  Period  pertaining  to a Loan that begins on the last
Business Day of a calendar  month (or on a day for which there is no numerically
corresponding  day in the  calendar  month at the end of such  Interest  Period)
shall end on the last Business Day of the last  calendar  month of such Interest
Period;

         (C) no Interest Period shall extend beyond the Maturity Date; and

         (D) no Interest  Period shall extend  beyond any date upon which is due
any  scheduled  principal  payment in respect of the Loan  unless the  aggregate
principal  amount  of the Loan is equal to or in  excess  of the  amount of such
principal payment.

         Interest  shall accrue at the Interest  Rate on all  principal  amounts
outstanding hereunder.  Commencing on January 1, 1997, interest shall be payable
quarterly in arrears,  on the first day of each Interest Period until October 1,
1997 and on December 31, 1997.  Thereafter,  accrued  interest  shall be payable
monthly  in  arrears  on  February  1,  1998,  March 1, 1998 and April 1,  1998.
Interest  shall  also be  payable  on the date of any  prepayment  of this  Loan
pursuant to Section  2.07 of the Loan  Agreement  for the portion of the Loan so
prepaid and upon payment  (including  prepayment) in full thereof and, after the
occurrence and during the continuance of any Event of Default, interest shall be
payable on demand.

<PAGE>

         Borrower  shall  make one  payment  of  principal  in the amount of One
Million Dollars ($1,000,000) on December 31, 1997 and thereafter all outstanding
principal,  together with all accrued  interest and all other amounts  otherwise
payable hereunder, shall be due and payable on the Maturity Date.

         Notwithstanding  the  foregoing,  if the Borrower shall fail to pay any
then due  principal  amount or interest or other amount  payable by the Borrower
under the Loan  Agreement  or under this Note within ten (10) days after the due
date,  such amount shall bear  interest from the original due date at a rate per
annum that is equal to the lesser of (i) five  percent (5%) higher than the then
applicable  Interest  Rate or (ii) the maximum  permissible  interest rate under
applicable Law until such overdue principal amount,  interest or other amount is
paid in full  (both  before  and after  judgment)  whether  or not any notice of
default in the payment thereof has been delivered under the Loan Agreement.

         Notwithstanding any provision of this Note or the Loan Agreement to the
contrary, it is the intent of the Lender and the Borrower that the Lender or any
subsequent  holder of this Note shall never be  entitled  to  receive,  collect,
reserve  or apply,  as  interest,  any amount in excess of the  maximum  rate of
interest permitted to be charged by applicable Law, as amended or enacted,  from
time to time. In the event Lender,  or any subsequent  holder of this Note, ever
receives,  collects,  reserves or applies,  as interest,  any such excess,  such
amount which would be excessive interest shall be deemed a partial prepayment of
principal and treated as such, or, if the principal  indebtedness  and all other
amounts due are paid in full,  any remaining  excess funds shall  immediately be
paid  to the  Borrower.  In  determining  whether  or not the  interest  paid or
payable,  under any specific  contingency,  exceeds the highest lawful rate, the
Bor rower and the Lender shall, to the maximum extent permitted under applicable
law, (a) exclude voluntary  prepayments and the effects thereof as it may relate
to any fees charged by the Lender,  and (b)  amortize,  prorate,  allocate,  and
spread, in equal parts, the total amount of interest  throughout the entire term
of the Note;  provided  that if the Note is paid and  performed in full prior to
the end of the full contemplated  term hereof,  and if the interest received for
the actual  period of existence  hereof  exceeds the maximum  lawful  rate,  the
Lender or any  subsequent  holder of the Note shall  refund to the  Borrower the
amount of such excess or credit the amount of such excess  against the principal
portion of the Note,  as of the date it was  received,  and, in such event,  the
Lender  shall  not be  subject  to  any  penalties  provided  by  any  laws  for
contracting  for,  charging,  reserving or  receiving  interest in excess of the
maximum lawful rate.

         Upon the  occurrence of any one or more Events of Default  specified in
the Loan Agreement,  all amounts then remaining unpaid on this Note shall be, or
may be  declared  to be,  immediately  due and  payable as  provided in the Loan
Agreement,  without  further  notice,  at the option of the holder  hereof.  The
holder may waive any Event of Default before or after the same has been declared
and  restore  this Note to full force and effect  without  impairing  any rights
hereunder,  such  right of waiver  being a  continuing  one,  but one waiver not
implying any additional or subsequent waiver.

         Demand,  presentment,  notice and protest are expressly waived,  except
for notices otherwise expressly required in the Loan Agreement.

         In the event this Note is placed in the hands of one or more  attorneys
for collection or enforcement or protection of the holder's rights  described in
the Loan Agreement,  the Borrower  agrees to pay all reasonable  attorney's fees
and all court and other out-of-pocket costs incurred by the holder hereof (which
shall be due on demand).

         This Note may be prepaid in accordance  with the  provisions of Section
2.07 of the Loan Agreement.

<PAGE>

         This Note is governed by and shall be construed in accordance  with the
internal laws of the State of New York.

         This Note may not be changed, extended or terminated except in writing.

         This Note may be assigned in  accordance  with Section 8.18 of the Loan
Agreement.  In the  event  of any  conflict  between  this  Note  and  the  Loan
Agreement, the provisions of the Loan Agreement shall control.

         This  Amended  and  Restated  Note is an  amendment,  modification  and
restatement of that certain Note in the original  principal amount of $3,750,000
(plus  capitalized  interest),  dated as of May 28, 1993,  issued by Borrower to
Lender,  previously  amended and restated by an Amended and  Restated  Equipment
Note in the original principal amount of $7,500,000 (plus capitalized  interest)
dated as of April 8, 1994 and by an Amended and Restated  Note in the  principal
amount of  $5,933,095.61  dated  October  1, 1996 (as  previously  amended,  the
"Original Note"). The principal amount of this Note is the outstanding principal
amount  of the  Original  Note,  including  interest  capitalized  and  added to
principal as provided therein. This Note is not a novation, release or discharge
of the indebtedness evidenced by the Original Note.

         Executed as of December 19th, 1997.

                                                  AMSC SUBSIDIARY CORPORATION


                                              By:/s/Richard J. Burnheimer
                                                 ------------------------

                                              Title:  Vice President & Treasurer
                                                      --------------------------




                                                                 Exhibit 10.24d
                                                                 --------------

                                 Addendum No. 3
                                       to
                            VOLUME PURCHASE AGREEMENT

         This Addendum No. 3 to VOLUME PURCHASE  AGREEMENT (this  "Addendum") is
hereby  entered  into  by  AMSC  Subsidiary  Corporation  ("AMSC")  and  TRIMBLE
NAVIGATION LIMITED ("TRIMBLE") on the date last indicated below.

                                    RECITALS

A.       TRIMBLE and AMSC entered into a certain VOLUME PURCHASE AGREEMENT dated
         March 10,  1995,  as amended on December  19, 1995 and later on January
         29, 1997 (collectively, the "Agreement").

B.       TRIMBLE and AMSC intend to further  amend the  Agreement  to reduce the
         shipment rate of Galaxy Production Units (as defined in the Agreement).

C. TRIMBLE and AMSC therefore hereby modify the Agreement as follows:

                                    ADDENDUM

1.       REDUCTION OF SHIPMENT RATE

         Beginning  August  1997,  Trimble  will  reduce  the  number  of Galaxy
         Production  Units  shipped  to AMSC  from  five  hundred  (500)  Galaxy
         Production Units per month to two hundred fifty (250) Galaxy Production
         Units per month, and AMSC shall purchase such units at such rate, until
         AMSC has purchased the number of such Galaxy  Production Units required
         by the Agreement.

2.       PRICES

         Prices for Units  shipped to AMSC  through  November  1997 shall remain
         unchanged  at one  thousand  six  hundred  seventy  five  U.S.  Dollars
         ($1,675). Beginning with the Galaxy Production Units shipped to AMSC in
         December,  1997 the price per unit will increase to one thousand  seven
         hundred fifty U.S. Dollars ($1,750).

3.       PREPAYMENT

         3.1      In accordance with the Agreement, AMSC has prepaid Trimble one
                  million  six  hundred  seventy  five  thousand  U.S.   Dollars
                  ($1,675,000)  for  Galaxy  Production  Units  scheduled  to be
                  shipped  through  at the  rate of five  hundred  (500)  Galaxy
                  Production  Units  per month  for the  months  of  August  and
                  September,  1997.  Due to the  reduction  in shipment  rate as
                  provided  above,  this prepaid  amount shall be  sufficient to
                  prepay for shipment through November, 1997.

         3.2      The prepayment due for December, 1997 shipment of  two hundred
                  fifty (250)  Galaxy  Production  Units  shall  be  prepaid  as
                  follows:

                  3.2.1    Two hundred  eighteen  thousand  seven  hundred fifty
                           U.S.  Dollars  ($218,750)  shall be paid on or before
                           October 15, 1997, and

                  3.2.2    Two hundred  eighteen  thousand  seven  hundred fifty
                           U.S.  Dollars  ($218,750)  shall be paid on or before
                           November 1, 1997.

                  Trimble's  obligation   to  ship  the  December,  1997  Galaxy
Production Units is conditioned upon


<PAGE>


                  Trimble's timely receipt of such prepayments.

         3.3      Beginning  November  15,  1997,  AMSC will  continue to prepay
                  Trimble for Galaxy  Production  Units on or before the 15th of
                  each  month for the  shipment  two  months  later  (e.g.,  the
                  payment for the two  hundred  fifty  (250)  Galaxy  Production
                  Units to be shipped January,  1997 shall be due and payable on
                  or before November 15, 1997.) Trimble's obligation to ship the
                  Galaxy  Production  Units is conditioned upon Trimble's timely
                  receipt of such prepayments.

4.       INCREASE OF SHIPMENT RATE

         4.1      Upon  forty-five  (45) days  prior  written  notice,  AMSC may
                  instruct  Trimble to resume shipping at a rate of five hundred
                  (500) Galaxy  Production Units per month on a sustained basis.
                  Such instruction shall be irrevocable.

         4.2      Upon such  instruction  to increase the shipment  rate to five
                  hundred  (500)  Galaxy  Production  Units  per  month and as a
                  condition  of  Trimble's   obligation   to  ship  such  Galaxy
                  Production Units:

                  4.2.1    At least  forty-five  days  prior to the first day of
                           the month in which Trimble makes the first  increased
                           shipment.  AMSC shall make a prepayment to Trimble of
                           eight hundred thirty seven thousand five hundred U.S.
                           Dollars ($837,500);

                  4.2.2    AMSC shall make  prepayments  of eight hundred thirty
                           seven thousand five hundred U.S. Dollars  (:$837,500)
                           on or before the 15th of each month; and

                  4.2.3    The price of each Galaxy Production Unit shall be one
                           thousand  six  hundred  seventy  five  U.S.   Dollars
                           ($1,675).

5.       RATIFICATION OF THE AGREEMENT

         In all other  respects,  TRIMBLE and AMSC hereby  ratify and affirm the
Agreement.

WITH INTENT TO BE BOUND,  TRIMBLE and AMSC have  signed  this  Amendment  on the
dates written below.

              TRIMBLE NAVIGATION LIMITED          AMSC SUBSIDIARY CORPORATION

Signature:    /s/Tom Ellis                        /s/Stephen D. Peck
              ------------                        ------------------
Typed
Name:         Tom Ellis                           Stephen D. Peck

Title:        Vice President, Mobile Position     Chief Financial Officer
              & Communications 

Date:         8/28/97                             8/29/97
              -------                             -------





                                                                  Exhibit 10.35a
                                                                  --------------
                                 AMENDMENT NO. 1
                TO AGREEMENT ENTERED INTO AS OF DECEMBER 14, 1992
           BY GTE SPACENET CORPORATION AND AMSC SUBSIDIARY CORPORATION

         Reference  is made to the  Agreement  entered  into as of December  14,
1992,  by GTE Spacenet  Corporation  (as assumed by GE American  Communications,
Inc.)  ("Americom")  and AMSC  Subsidiary  Corporation  ("AMSC") with respect to
conduct  of  certain  satellite  operations  on a  non-interference  basis  (the
"Agreement").  Capitalized  terms used herein without  definition shall have the
respective meanings set forth in this Agreement.

         WHEREAS,  AMSC is  considering a  transaction  whereby the satellite it
operates at 101 degrees W.L. may have modified telemetry carrier parameters from
those anticipated in the Agreement;

         WHEREAS,  AMSC has discussed  these  potential  technical  changes with
Americom,  and Americom has indicated that such changes could be accommodated in
the Agreement.

         NOW THEREFORE, the parties agree to amend the Agreement as follows:

         1.  Exhibits  1 and 2 to the  Agreement  shall be amended to provide an
alternative  Frequency  (MHz) for the Telemetry  Carrier  Parameters,  at either
11700.5, 11702.75, or 11701.0 in accordance with the attached revised Exhibits 1
and 2.

         2. Americom  recognizes that AMSC's  discussions  include the potential
sharing of ownership and use of AMSC-1,  and may include a substitute  satellite
to be located at 101 degrees  W.L.,  consistent  with revised  Exhibits 1 and 2.
Americom  agrees  that  such  shared  ownership  and  use  and  substitution  is
consistent with the terms of the Agreement, as amended herein.

         3. The  information  provided herein shall be subject to the provisions
of Section 7.9 of the Agreement.

         4. Except as expressly  modified herein,  the Agreement shall remain in
full force and effect.

         IN WITNESS THEREOF,  the parties have entered into this amendment as of
the 7th day of November, 1997.

   AMSC SUBSIDIARY CORPORATION                        GE AMERICAN
                                                      COMMUNICATIONS, INC.

   /s/ Randy Segal                                    /s/ Philip V. Otero
   By: Randy Segal                                    By: Philip V. Otero
   ---------------                                    -------------------
   Title: Vice President and                          Title: Sr. Vice President
          General Counsel


<PAGE>



                                    Exhibit 1
<TABLE>
<CAPTION>

                 AMSC TELEMETRY, TRACKING AND COMMAND PARAMETERS



<S>                                                        <C>                       <C>                   <C>
COMMAND PARAMETERS                                           Frequency 1               Frequency 2         Units


         Frequency                                             14449.5                   14000.5           MHz
         Maximum Flux Density                                   -85.0                    -100.0            dBW/m2
         Antenna Coverage                                        Omni                 North America
         Polarization                                          Vertical                Horizontal
         Modulation                                               FM                       FM
         Peak Deviation                                          300                       300             kHz
         Occupied Bandwidth                                       1                         1              MHz
         Emission Designator                                   700KF9D                   700KF9D

TELEMETRY CARRIER PARAMETERS

         Frequency                                             11701.0                 11700.5 or          MHz
                                                                                        11702.75*
         Antenna:  Switchable between omni and directive                                                             
         Modulation                                        Phase, 1 radian           Phase, 1 radian
         Occupied Bandwidth                                      100                       100             kHz
         Emission Designator                                   138KGXD
         Frequency Stability                                    +/-50                     +/-50            kHz

SATELLITE TELEMETRY ANTENNA PARAMETERS:  
  If uses TMI Satellite currently at 106.5 degrees


         Antenna                                                 Omni                   Directive
         Polarization                                         Horizontal                Vertical
         Peak EIRP                                              7.4 dBW                 17.5 dBW

SATELLITE TELEMETRY ANTENNA PARAMETERS:  
  If continue to use AMSC-1


         Antenna                                                 Omni                   Directive
         Polarization                                         Horizontal                Vertical
         Antenna                                               9 dBW                     11 dBW

TT&C EARTH STATION CHARACTERISTICS

     A.  FOR 8 METER ANTENNA DIAMETER TT&C EARTH STATION:
         Antenna Diameter                                      8 meters
         On Axis Receive Gain                                  58.5 dBi
         On Axis Transmit Gain                                 59.5 dBi

         Off Axis Gain                                       29-25*LOG (theta) dBi
                                                            for theta greater than 
                                                             or equal to 1 degree

         G/T                                                   34 dB/K
         Polarization                                           Linear

     B.  FOR 11 METER ANTENNA DIAMETER TT&C EARTH STATION:
         Antenna Diameter                                      11 meters
         On Axis Receive Gain                                  60 dBi
         On Axis Transmit Gain                                 61 dBi

         Off Axis Gain                                       29-25*LOG (theta) dBi
                                                            for theta greater than 
                                                             or equal to 1 degree

         G/T                                                   37 dB/K
         Polarization                                           Linear


</TABLE>
* The telemetry  transmitter tuned to 11702.75 MHz will operate only through the
omni  antenna  after  GE  American   Communications   Inc.  begins  operating  a
replacement  for its current  satellite  at 101 degrees  West.  The maximum EIRP
radiated on this frequency at horizontal  polarization will be +7.5 dBW in a 100
kHx bandwith.






<PAGE>




                                    Exhibit 2
               --------------------------------------------------


                            GE TRANMISSION PARAMETERS

EARTH-TO-SPACE DIRECTION


   Maximum,  co-polarized  power  flux  density  in 1 MHz  toward  the
   satellite at 101 degrees West:

             -130dBW/m2       at 14000.5 MHz


             -115dBW/m2       at 14499.5 MHz


SPACE-TO-EARTH DIRECTION


    Maximum, satellite co-polarized EIRP in 100 kHz


             -20dBW at 11700.5 MHz and 11701.0 MHz


    Maximum, satellite co-polarized EIRP in 100 kHz toward:
    Allan Park, Ontario, Canada; and Edmunton, Alberta, Canada

             -15.6dBW at 11702.75 MHz





<PAGE>








                                                                   Exhibit 10.64
                                                                   -------------


                              BRIDGE LOAN AGREEMENT


                  BRIDGE LOAN  AGREEMENT,  dated as of December 30, 1997,  (this
"Agreement")  made  by  and  among  AMSC  Subsidiary  Corporation,   a  Delaware
corporation  dually  incorporated as a Virginia Public Service  corporation (the
"Borrower"),  American Mobile Satellite Corporation, a Delaware corporation (the
"Parent  Guarantor")  and Hughes  Communications  Satellite  Services,  Inc.,  a
California corporation (the "Lender").

                              W I T N E S S E T H :

                  WHEREAS,  the  Borrower  has  requested  that the Lender  make
secured bridge term loans to the Borrower in an aggregate principal amount of up
to $10,000,000 which the Borrower will use for general corporate purposes; and

                  WHEREAS,  the Lender has agreed to make  secured  bridge  term
loans to the  Borrower,  but only upon the terms and  subject to the  conditions
contained herein.

                  NOW,  THEREFORE,  in  consideration of the premises and of the
mutual covenants herein contained and for other good and valuable consideration,
the  receipt  of which is  hereby  acknowledged,  the  parties  hereto  agree as
follows:

                  1.  Defined  Terms.  The  following  terms  when  used in this
Agreement  shall  have the  following  meanings  (such  meanings  being  equally
applicable to both the singular and plural forms of the terms defined):

                  "Agreement" shall mean this Bridge Loan Agreement, as the same
         may be amended,  modified or otherwise  supplemented  from time to time
         and  shall  refer to this  Agreement  as in  effect  on the  date  such
         reference becomes operative.

                  "AMRC" shall mean American Mobile Radio Corporation, a
         Delaware corporation.

                  "AMSC Pledge Agreement" shall mean the Pledge Agreement, dated
         as of the  date  hereof,  executed  by the  Parent  Guarantor,  as such
         agreement may be amended,  supplemented or otherwise modified from time
         to time,  pursuant to which the Parent  Guarantor  shall  pledge to the
         Lender the Pledged Collateral referred to therein, including the common
         stock of AMRC Holdings,  Inc. owned by the Parent Guarantor,  to secure
         the Secured Obligations of the Borrower.

                  "Business  Day" shall mean any day that is not a  Saturday,  a
         Sunday or a day on which banks are  required or  permitted to be closed
         in the States of New York or California.

                  "Closing Date" shall mean the date hereof.


<PAGE>


                  "Corporation"  shall  mean each of the  Borrower,  the  Parent
         Guarantor and AMRC Holdings, Inc.

                  "Event of Default" shall have the meaning specified in
         Section 6(a) hereof.

                  "Governmental Authority" shall mean any nation or gov ernment,
         any state or other political  subdivision thereof, any central bank (or
         similar  monetary  or  regulatory   authority)   thereof,   any  entity
         exercising   executive,    legislative,    judicial,    regulatory   or
         administrative  functions  of or  pertaining  to  government,  and  any
         corporation  or other  entity  owned or  controlled,  through  stock or
         capital ownership or otherwise, by any of the foregoing.

                  "hereby," "herein," "hereof," "hereunder" and words of similar
         import  refer  to  this  Agreement  as  a  whole  (including,   without
         limitation,  any  schedules  hereto)  and not  merely  to the  specific
         section, paragraph or clause in which the respective word appears.

                  "Lender" shall mean Hughes Communications Satellite
         Services, Inc. or its successors or assigns.

                  "Lien"  shall  mean any  mortgage  or deed of  trust,  pledge,
         hypothecation,  assignment,  deposit arrangement,  lien, charge, claim,
         security interest, easement or encumbrance, or prefer ence, priority or
         other  security  agreement or  preferential  arrangement of any kind or
         nature whatsoever  (including,  without limitation,  any lease or title
         retention agreement,  any financing lease having substantially the same
         economic  effect  as  any of the  foregoing,  and  the  filing  of,  or
         agreement  to give,  any  financing  statement  perfecting  a  security
         interest under the UCC or comparable law of any jurisdiction).

                  "Loan" shall have the meaning specified in Section 2(a)
         hereof.

                  "Loan Documents" shall mean this Agreement,  the Term Note and
         the AMSC Pledge Agreement.




                                        2




<PAGE>



                  "Material Adverse Effect" shall mean a material adverse change
         in, or a  material  adverse  effect  upon,  any of (a) the  operations,
         business, properties,  condition (financial or otherwise) of either the
         Parent Guarantor or the Borrower and its Subsidiaries taken as a whole;
         (b) the ability or prospective ability of the Parent Guarantor,  or the
         Borrower  to  perform  under  any  Loan  Document;  (c)  the  legality,
         validity,  binding effect or enforceability  of any Loan Document;  (d)
         the  perfection  or priority of any Lien  granted the Lender  under the
         AMSC Pledge Agreement; or (e) the Pledged Collateral.

                  "Maturity Date" shall mean March 31, 1999.

                  "Maximum Commitment Amount" shall mean $10,000,000.

                  "Maximum  Term Loan Amount"  shall mean the maximum  aggregate
         principal amount of Term Loans outstanding as of such date as set forth
         in Schedule I hereto.

                  "Morgan Credit  Agreement" shall mean the $150,000,000  Credit
         Agreement, dated as of June 28, 1996 among AMSC Subsidiary Corporation,
         American Mobile Satellite Corporation, the banks listed therein, Morgan
         Guaranty Trust Company of New York, as Documentation Agent, and Toronto
         Dominion (Texas),  Inc., as Administrative  Agent, as amended from time
         to time and giving effect to any waivers granted thereunder.

                  "Net  Proceeds"  shall mean for any asset  disposition,  lease
         agreement,  financing or equity transaction the aggregate cash proceeds
         received by the Parent  Guarantor or any of its Subsidiaries in respect
         of such transaction  (including any non-cash  proceeds thereof that are
         thereafter  sold or disposed of for, or otherwise  give rise to, cash),
         net of  direct  out-of-pocket  costs  of the  Parent  Guarantor  or its
         Subsidiaries relating to such transaction.

                  "Person"  shall  mean  any  individual,  sole  proprietorship,
         partnership,   joint  venture,  trust,   unincorporated   organization,
         association,  corporation,  institution,  public  benefit  corporation,
         entity or government (whether federal,  state,  county, city, municipal
         or  otherwise,  including,  without  limitation,  any  instrumentality,
         division, agency, body or department thereof).



                                        3




<PAGE>



                  "Pledged  Collateral" shall mean all property and interests in
         property  and proceeds  thereof now owned or hereafter  acquired by the
         Parent  Guarantor  in or upon  which a Lien is  granted  under the AMSC
         Pledge Agreement.

                  "Pledged  Shares"  shall mean the capital stock covered by the
         AMSC Pledge Agreement.

                  "Projections"  shall mean the financial  projections  covering
         the months December,  1997 through March, 1999,  inclusive,  heretofore
         delivered  to  the  Lender  by the  Borrower,  referred  to in  Section
         3(a)(vi).

                  "Requirement  of  Law"  means,  as  to  any  Person,  any  law
         (statutory or common),  treaty,  rule or regulation or determination of
         an arbitrator or of a Governmental  Authority,  in each case applicable
         to or binding  upon the Person or any of its  property  or to which the
         Person or any of its property is subject;  in any case,  non-compliance
         with which by either of the Parent  Guarantor  or the Borrower or their
         Subsidiaries  could  reasonably be expected to have a Material  Adverse
         Effect.

                  "Secured  Obligations"  shall mean all of the unpaid principal
         amount of, and  accrued  interest  on, the Term Note,  and all  amounts
         payable to Lender under this  Agreement  and the AMSC Pledge  Agreement
         together with all costs of the Lender,  including,  without limitation,
         reasonable attorneys' fees, incurred in connection with the enforcement
         of any of its rights and remedies hereunder and thereunder.

                  "Subsidiary"  shall mean, with respect to any Person,  (a) any
         corporation  of which an aggregate of more than 50% of the  outstanding
         stock having  ordinary voting power to elect a majority of the board of
         directors of such corporation  (irrespective  of whether,  at the time,
         stock of any other class or classes of such  corporation  shall have or
         might have voting power by reason of the happening of any  contingency)
         is at the time,  directly or indirectly,  owned legally or beneficially
         by such Person and/or one or more Subsidiaries of such Person,  and (b)
         any partnership in which such Person and/or one or more Subsidiaries of
         such Person  shall have an  interest  (whether in the form of voting or
         participation in profits or capital contribution) of more than 50%.



                                        4




<PAGE>



                  "Term Note" shall have the meaning specified in Section
         2(a) hereof.

                  "UCC" shall mean the Uniform  Commercial Code as the same may,
         from time to time,  be in  effect  in the State of New York;  provided,
         however,  in the event that, by reason of mandatory  provisions of law,
         any or all of the  attachment,  perfection  or priority of the Lender's
         security interest in any Pledged  Collateral is governed by the Uniform
         Commercial Code as in effect in a jurisdiction  other than the State of
         New York, the term "UCC" shall mean the Uniform  Commercial  Code as in
         effect in such other jurisdiction for purposes of the provisions hereof
         relating to such attachment, perfection or priority and for purposes of
         definitions related to such provisions.

                  2.       Loan Provisions

                  (a)  Loans.  On  the  terms  and  subject  to  the  conditions
contained  in this  Agreement,  the Lender  agrees to make term loans (the "Term
Loans") to the Borrower  from time to time from the Closing Date until March 31,
1998; provided that the aggregate amount of the Term Loans shall not on any date
exceed  the  Maximum  Term Loan  Amount  for such date set forth in  Schedule  I
hereto.  The  Borrower  shall give  Lender at least  three  Business  Days prior
written notice of each Loan,  specifying the amount and date thereof.  Each Loan
will be at least $100,000 or a larger multiple thereof.

                  The Term Loans shall collectively be referred to as the "Loan"
and the Loan shall be evidenced by a promissory note,  substantially in the form
attached hereto as Exhibit A ("Term Note"),  to be executed and delivered by the
Borrower on the Closing Date.

                  (b) Payments.  (i) All payments and  prepayments  made on each
Term Loan  shall be made in lawful  money of the  United  States of  America  in
immediately  available  funds no later than 12 o'clock Noon,  New York, New York
time, at Bank of America, Concord, California, Account No. 12356-06628,  Account
Name: Hughes  Electronics  Corp., ABA No. 121000358,  or such other place as the
Lender  shall  designate  on the date  such  payment  is due in  writing  to the
Borrower.

                         (ii) If any payments or prepayment on a Term Loan shall
                    become  due on a day  which  is  not a  Business  Day,  such
                    payment or prepayment  shall be made on the next  succeeding
                    Business  Day and such  extension of time shall in such case
                    be included in computing  interest in  connection  with such
                    payment or prepayment.


                                        5




<PAGE>



                         (iii) All payments made by the Borrower hereunder shall
                    be made without setoff, counterclaim or other defense.

                  (c) Repayment of Principal.  The principal amount of each Term
Loan shall be payable, together with accrued and unpaid interest thereon, on the
Maturity Date.

                  (d) Mandatory Prepayment. If on or after the Closing Date, the
Parent Guarantor or any of its  Subsidiaries  (other than AMRC or AMRC Holdings,
Inc.) shall receive Net Proceeds from any asset  disposition,  lease  agreement,
financing or equity  transaction,  Borrower shall immediately apply all such Net
Proceeds to prepay the Loan. Any amounts so prepaid may not be reborrowed.

                  (e) Optional  Prepayment.  The Borrower  may, at any time upon
notice to the Lender stating the proposed date and aggregate principal amount of
the prepayment,  prepay,  without penalty or premium, the outstanding  principal
amount of the Loan in whole or in part,  together  with accrued  interest to the
date of such prepayment on the principal amount prepaid; provided, however, that
each partial prepayment shall be in an aggregate  principal amount not less than
$100,000  or integral  multiples  of  $100,000  in excess  thereof.  Any amounts
prepaid may not be reborrowed. Upon the giving of such notice of prepayment, the
principal  amount of the Loan  specified  to be  prepaid  shall  become  due and
payable on the date specified for such prepayment.

                  (f)  Interest.   The  Borrower   shall  pay  interest  on  the
outstanding  principal  amount of each Term Loan for each day from and including
the date such Term Loan is made to but excluding the date such Term Loan is paid
in full to the Lender, monthly in arrears on the last Business Day of each month
("Interest  Payment  Date")  commencing on the first such date after the date of
the initial Term Loan, at a rate equal to 12% per annum, based on a 360-day year
of twelve 30-day  months for the actual  number of days  elapsed;  provided that
while an Event of  Default  is  continuing  each Term Loan and all  amounts  due
hereunder shall bear interest at a rate of 14% per annum.




                                        6




<PAGE>




                  (g)  Proceeds.  The Borrower  shall apply the proceeds of each
Term Loan for general  corporate  purposes.  None of such proceeds shall be used
directly or  indirectly  for the purpose of buying or  carrying  "margin  stock"
within the meaning of Regulation G of the Federal Reserve Board.

                  3.       Conditions Precedent.

                  (a) Conditions  Precedent to Initial Term Loan. The obligation
of the  Lender to make its  initial  Term Loan to the  Borrower  is  subject  to
satisfaction of the conditions precedent that the Lender shall have received, on
the Closing  Date,  the  following,  in form and substance  satisfactory  to the
Lender:

                         (i) Counterparts of this Agreement duly executed by the
                    Parent Guarantor, the Borrower and the Lender.

                         (ii) Term Note of the  Borrower  dated the Closing Date
                    payable  to the order of the  Lender in a  principal  amount
                    equal to the Maximum Commitment Amount.

                         (iii)  A  copy  of  the  articles  or   certificate  of
                    incorporation  (or other  organizational  documents)  of the
                    Parent  Guarantor,  the Borrower,  AMRC  Holdings,  Inc. and
                    AMRC,  certified  as of a recent  date by the  Secretary  of
                    State of the state of incorporation of such entity, together
                    with  certificates  of such officials  attesting to the good
                    standing of such entity.

                         (iv) An executed copy of a favorable opinion of counsel
                    to the  Borrower as to matters as the Lender may  reasonably
                    request.

                         (v) The AMSC  Pledge  Agreement,  duly  executed by the
                    Parent Guarantor, together with:

                           (A)  certificates  representing  the Pledged  Shares,
                  together  with  undated  stock  powers for such  certificates,
                  executed in blank; and

                           (B) evidence that all other actions necessary,  or in
                  the  opinion of the Lender,  desirable  to perfect and protect
                  the Lien created by the aforementioned AMSC Pledge



                                        7




<PAGE>


                  Agreement  have  been  taken   including  the  filing  of  UCC
                  financing statements.

                         (vi)   Projections   by  the   Borrower   of  (i)   the
                    consolidated  results of operations and changes in financial
                    position  of  Borrower  and its  Subsidiaries  on a  monthly
                    basis, from December 1997 through March 1999, inclusive, and
                    (ii) the consolidated  balance sheet of the Borrower and its
                    Subsidiaries  as of the last day of each month  during  such
                    period  based  upon all  information  known to the  Borrower
                    which is pertinent thereto; such Projections shall have been
                    made  by the  Borrower  on a  reasonable  basis  and in good
                    faith.

                         (vii) Balance sheet,  income statement and statement of
                    cash  flow  of the  Borrower  and  its  Subsidiaries,  which
                    financial  statements shall present fairly,  in all material
                    respects,  the  financial  position of the  Borrower and its
                    Subsidiaries as at September 30, 1997.

                         (viii)  A  certificate,  signed  by an  officer  of the
                    Borrower,  stating  that on the Closing  Date the  following
                    statements are true and correct with respect to the Borrower
                    and its Subsidiaries:

                           (A)  All  necessary   approvals   from   Governmental
                  Authorities  and all  necessary  approvals  from third parties
                  required  to be  obtained  in  connection  with the making and
                  performance  of this  Agreement and the AMSC Pledge  Agreement
                  and the  transactions  contemplated  hereby have been obtained
                  and remain in effect.

                           (B) There exists no judgment,  order,  injunction  or
                  other  restraint  prohibiting or imposing  materially  adverse
                  conditions  upon the Loan  and the  transactions  contemplated
                  hereby.

                           (C)   There   exists   no   claim,    action,   suit,
                  investigation or proceeding  (including,  without  limitation,
                  shareholder  or  derivative  litigation)  pending  or,  to the
                  knowledge  of  the  Borrower  or  any  of  its   Subsidiaries,
                  threatened   in  any  court  or  before  any   arbitrator   or
                  Governmental  Authority  which  relates  to,  the Loan and the
                  transactions contemplated hereby or which has



                                        8




<PAGE>



                  a reasonable likelihood of having a material adverse effect on
                  the  Loan  and  the  transactions  contemplated  hereby  or  a
                  Material Adverse Effect.

                           (D) There  shall not occur as a result of the  making
                  and   performance  of  this  Agreement  and  the  AMSC  Pledge
                  Agreement and the transactions  contemplated  hereby a default
                  (or any event which with the giving of notice or lapse of time
                  or both would be a default) under  contractual  obligations of
                  or relating to any Corporation.

                         (ix) Such additional documents,  information (including
                    financial  information)  and  materials  as the  Lender  may
                    reasonably request.

                  (b) Conditions  Precedent to Each Term Loan. The obligation of
the  Lender to make any Term  Loan  (including  the  initial  Term  Loan) to the
Borrower shall be subject to the further conditions precedent that:

                         (i) The following  statements shall be true on the date
                    of such Term Loan,  before and after giving  effect  thereto
                    and to the  application  of the proceeds  therefrom (and the
                    acceptance by the Borrower of the proceeds of such Term Loan
                    shall  constitute  a  representation  and  warranty  by  the
                    Borrower that on the date of such Term Loan such  statements
                    are true):

                           (A) The  representations and warranties of the Parent
                  Guarantor,  the  Borrower  and its  Subsidiaries  contained in
                  Section 4 hereof are  correct on and as of such date as though
                  made on and as of such date;

                           (B) No Event of Default or event  which with lapse of
                  time or lack of notice  would have  become an Event of Default
                  has  occurred and is  continuing  or will result from the Term
                  Loan being made on such date; and

                           (C) The financial performance of the Borrower and its
                  Subsidiaries  shall  be not  less  than  as set  forth  in the
                  Projections  provided  by the  Borrower  pursuant  to  Section
                  3(a)(vi) hereof.




                                        9




<PAGE>



                         (ii) The making of the such Term Loan on such date does
                    not  violate  any  Requirement  of Law and is not  enjoined,
                    temporarily, preliminarily or permanently.

                         (iii) The Lender shall have  received  such  additional
                    documents,  information  and  materials  as the  Lender  may
                    reasonably request.


                  4.   Representations  and  Warranties.   Each  of  the  Parent
Guarantor, the Borrower and its Subsidiaries hereby represents and warrants that
as of the Closing Date:

                  (a) Each  Corporation is duly  incorporated,  validly existing
and in good standing under the laws of its jurisdiction of incorporation and has
the requisite corporate power to make and perform the Loan Documents to which it
is a party  and each  Loan  Document  has been  duly  authorized,  executed  and
delivered by each Corporation  party thereto and constitutes a legal,  valid and
binding obligation of such Corporation enforceable in accordance with its terms.

                  (b) The  execution,  delivery  and  performance  of each  Loan
Document by each  Corporation  party thereto does not: (i) contravene its or any
of its Subsidiaries' respective certificate of incorporation or by-laws or other
comparable governing documents, (ii) violate any other applicable Requirement of
Law, or any order or decree of any Governmental  Authority or arbitrator,  (iii)
conflict  with or result in the breach of, or  constitute  a default  under,  or
result in or permit the termination or  acceleration  of, any of its contractual
obligations or any contractual obligations of its Subsidiaries or (iv) result in
the creation or  imposition of any Lien upon any of its property or the property
of any of its Subsidiaries,  other than those in favor of the Lender pursuant to
the AMSC Pledge Agreement; and

                  (c)  The   execution,   delivery   and   performance   by  the
Corporations of the Loan Documents and the transactions  contemplated hereby and
thereby does not and will not require the consent of, authorization by, approval
of, notice to, or filing or registration with, any Governmental Authority or any
other  Person,  other than those  which have been,  prior to the  Closing  Date,
delivered to the Lender.



                                       10




<PAGE>



                  (d) The  Projections  delivered to the Lender were prepared by
the Borrower on a reasonable basis and in good faith.

                  (e) There  exists no claim,  action,  suit,  investigation  or
proceeding (including, without limitation, shareholder or derivative litigation)
pending  or,  to the  knowledge  of  the  Borrower  or any of its  Subsidiaries,
threatened in any court or before any arbitrator or Governmental Authority which
relates  to, the Loan and the  transactions  contemplated  hereby or which has a
reasonable  likelihood of having a material  adverse  effect on the Loan and the
transactions contemplated hereby or a Material Adverse Effect.

                  (f) The  representations  and warranties made in Sections 4.7,
4.8, 4.9, 4.11,  4.12,  4.13, 4.14, 4.16 and 4.17 of the Morgan Credit Agreement
by the Borrower and the Parent Guarantor are correct (with references therein to
"the  Agreement"  meaning  this  Agreement,  to "Loan  Documents"  meaning  Loan
Documents  as defined  herein and to the  "Banks" or the  "Agents"  meaning  the
Lender)  as though  made to the Lender  with  respect to each Term Loan and this
Agreement.

                  5.  Covenants.  Each of the Parent  Guarantor and the Borrower
covenants  and  agrees  with the  Lender  that  from and  after the date of this
Agreement and until the Secured  Obligations  are fully  satisfied  such parties
shall comply with its covenants made in Article 5 of the Morgan Credit Agreement
(as such  Agreement is in effect on the date hereof without giving effect to any
amendments or waiver thereof after the date hereof and with  references  therein
to "the Agreement"  meaning this  Agreement,  to "Loan  Documents"  meaning Loan
Documents  as defined  herein and to the  "Banks" or the  "Agents"  meaning  the
Lender) as though  such  covenants  were made by such  party to the Lender  with
respect to the Loan and this Agreement; provided that the failure to comply with
any of the  provisions  of Sections  5.28 through 5.32 or the proviso in Section
5.33 of the Morgan Credit  Agreement shall not constitute a breach  hereunder so
long as such  failure  to comply  is not an Event of  Default  under the  Morgan
Credit Agreement.









                                       11




<PAGE>


                  6.  Events of Default; Rights and Remedies


                  (a) The occurrence of any one or more of the following  events
(regardless  of the  reason  thereof)  shall  constitute  an "Event of  Default"
hereunder:

                         (i) The  Borrower  shall  fail to make any  payment  of
                    principal  of, or  interest  on,  the Term Note when due and
                    payable or declared due and payable.

                         (ii) The  Borrower  shall fail or  neglect to  perform,
                    keep or observe any other provision of this Agreement or any
                    Loan  Document  and the same shall remain  unremedied  for a
                    period  ending  thirty  (30) days after the  Borrower  shall
                    receive written notice of any such failure from the Lender.

                         (iii) Any representation or warranty of any corporation
                    herein or in any Loan Document  shall be untrue or incorrect
                    in any material respect,  as of the date when made or deemed
                    made.

                         (iv) Any  "Event  of  Default"  shall  occur  under the
                    Morgan Credit Agreement.

                         (v) A case or  proceeding  shall  have  been  commenced
                    against any Corporation or AMRC in a court having  competent
                    jurisdiction  seeking a decree or order in  respect  of such
                    Corporation or AMRC, (A) under title 11 of the United States
                    Code, as now constituted or hereafter amended,  or any other
                    applicable  federal,  state or foreign  bankruptcy  or other
                    similar   law,  (B)   appointing   a  custodian,   receiver,
                    liquidator,  assignee,  trustee or sequestrator  (or similar
                    official) of such  Corporation or AMRC or of any substantial
                    part of its  properties,  or (C) ordering the  winding-up or
                    liquidation  of the affairs of such  Corporation or AMRC and
                    such case or proceeding shall remain undismissed or unstayed
                    for sixty (60)  consecutive days or such court shall enter a
                    decree or order  granting the relief  sought in such case or
                    proceeding.

                         (vi) Any  Corporation or AMRC shall (A) file a petition
                    seeking  relief under title 11 of the United States Code, as
                    now   constituted  or  hereafter   amended,   or  any  other
                    applicable  federal,  state or foreign  bankruptcy  or other
                    similar law, (B) consent to the  institution  of proceedings
                    thereunder  or to the filing of any such  petition or to the
                    appointment   of  or  taking   possession  by  a  custodian,
                    receiver, liquidator,  assignee, trustee or sequestrator (or
                    similar  official)  of any  Corporation  or  AMRC  or of any
                    substantial  part of its  properties,  (C) fail generally to
                    pay its  debts as such  debts  become  due,  or (D) take any
                    corporate action in furtherance of any such action.



                                       12




<PAGE>



                  (b)      Rights and Remedies Upon Event of Default . 
                           ------------------------------------------

If any Event of Default  specified  in Section  6(a) shall have  occurred and be
continuing, the Lender may by notice to the Borrower terminate its commitment to
make Term Loans hereunder and/or declare the Secured Obligations to be forthwith
due and payable,  whereupon all such Secured Obligations shall become and be due
and payable, without presentment, demand, protest or further notice of any kind,
all of which are expressly waived by the Borrower; provided, however, that  upon
                                                   --------  -------
the  occurrence  of an Event of Default  specified  in  Section  6(a)(v) or (vi)
hereof,  such  commitment to make Term Loans shall  automatically  terminate and
such Secured  Obligations  shall  automatically  become due and payable  without
declaration, notice or demand by the Lender.

                  7.       Parent Guaranty.

                  (a)  The  Parent   Guaranty.   The  Parent   Guarantor  hereby
unconditionally  guarantees  the full and  punctual  payment  (whether at stated
maturity,  upon  acceleration  or otherwise) of the principal of and interest on
the Term Note issued by the Borrower  pursuant to this  Agreement,  and the full
and  punctual  payment of all other  Secured  Obligations.  Upon  failure by the
Borrower to pay punctually any such amount, the Parent Guarantor shall forthwith
on demand pay the amount not so paid at the place and in the manner specified in
this Agreement.

                  (b)  Guaranty  Unconditional.  The  obligations  of the Parent
Guarantor  hereunder shall be  unconditional  and absolute and, without limiting
the generality of the foregoing, shall not be released,  discharged or otherwise
affected by:

                         (i) any  extension,  renewal,  settlement,  compromise,
                    waiver  or  release  in  respect  of any  obligation  of the
                    Borrower under this Agreement or the Term Note, by operation
                    of law or otherwise;




                                       13




<PAGE>



                         (ii) any  modification or amendment of or supplement to
                    this Agreement or the Term Note or any Loan Document;

                         (iii)  any  release,   impairment,   non-perfection  or
                    invalidity  of any  direct  or  indirect  security  for  any
                    obligation of the Borrower  under this Agreement or the Term
                    Note;

                         (iv) any change in the corporate  existence,  structure
                    or  ownership  of  any   Corporation,   or  any  insolvency,
                    bankruptcy,   reorganization  or  other  similar  proceeding
                    affecting  any  Corporation  or its assets or any  resulting
                    release  or  discharge  of any  obligation  of the  Borrower
                    contained in this Agreement or the Term Note;

                         (v) the existence of any claim, set-off or other rights
                    which the Parent  Guarantor may have at any time against the
                    Borrower,  the  Lender  or  any  other  Person,  whether  in
                    connection herewith or any unrelated transactions,  provided
                    that nothing  herein shall prevent the assertion of any such
                    claim by separate suit or compulsory counterclaim;

                         (vi) any invalidity or unenforceability  relating to or
                    against the Borrower for any reason of this Agreement or the
                    Term Note, or any provision of applicable  law or regulation
                    purporting  to prohibit  the payment by the  Borrower of the
                    principal  of or  interest  on the  Term  Note or any  other
                    amount payable by the Borrower under this Agreement; or

                         (vii) any other act or  omission to act or delay of any
                    kind by the Borrower,  the Lender or any other Person or any
                    other  circumstance  whatsoever  which  might,  but  for the
                    provisions  of  this   paragraph,   constitute  a  legal  or
                    equitable  discharge of the Parent  Guarantor's  obligations
                    hereunder.

                  (c)  Discharge  Only Upon Payments In Full;  Reinstatement  In
Certain Circumstances. The Parent Guarantor's obligations hereunder shall remain
in full force and effect  until the  principal  of and interest on the Term Note
and all  Secured  Obligations  shall have been paid in full.  If at any time any
payment  of the  principal  of or  interest  on the  Term  Note  or any  Secured
Obligations  is  rescinded or must be  otherwise  restored or returned  upon the
insolvency,  bankruptcy  or  reorganization  of the Borrower or  otherwise,  the
Parent Guarantor's  obligations  hereunder with respect to such payment shall be
reinstated at such time as though such payment had been due but not made at such
time.



                                       14




<PAGE>


                  (d)  Waiver by the  Parent  Guarantor.  The  Parent  Guarantor
irrevocably  waives  acceptance  hereof,  presentment,  demand,  protest and any
notice not provided for herein,  as well as any requirement that at any time any
action be taken by any Person against the Borrower or any other Person.

                  (e)  Subrogation.  Until  such  time as all  principal  of and
interest on the Term Note issued by the Borrower  pursuant to this Agreement and
all  Secured  Obligations  have  indefeasibly  been  paid in  full,  the  Parent
Guarantor shall not assert any rights to which it may be entitled,  by operation
of law or otherwise,  upon making any payment  hereunder to be subrogated to the
rights of the payee against the Borrower with respect to such payment or against
any  direct or  indirect  security  therefor,  or  otherwise  to be  reimbursed,
indemnified  or  exonerated  by or for the  account of the  Borrower  in respect
thereof.

                  (f)  Stay of  Acceleration.  If  acceleration  of the time for
payment of any amount  payable by the Borrower  under this Agreement or the Term
Note is stayed upon insolvency,  bankruptcy or  reorganization  of the Borrower,
all such  amounts  otherwise  subject  to  acceleration  under the terms of this
Agreement  shall  nonetheless  be  payable  by the  Parent  Guarantor  hereunder
forthwith on demand by the Lender.

                  8.  Reinstatement.  This Agreement  shall remain in full force
and effect and  continue  to be  effective  should any  petition  be filed by or
against the  Borrower for  liquidation  or  reorganization,  should the Borrower
become  insolvent or make an assignment for the benefit of creditors or should a
receiver or trustee be appointed for all or any  significant  part of any of the
Borrower's assets,  and shall continue to be effective or be reinstated,  as the
case may be, if at any time payment and performance of the Secured  Obligations,
or any part thereof,  is,  pursuant to applicable  law,  rescinded or reduced in
amount,  or must otherwise be restored or returned by any obligee of the Secured
Obligations,  whether as a "voidable preference",  "fraudulent  conveyance",  or
otherwise,  all as though such payment or performance  had not been made. In the
event that any payment, or any part thereof, is rescinded,  reduced, restored or
returned, the Secured Obligations shall be reinstated and deemed reduced only by
such amount paid and not so rescinded, reduced, restored or returned.



                                       15




<PAGE>


                  9. Notices.  Except as otherwise provided herein,  whenever it
is  provided  herein  that  any  notice,  demand,  request,  consent,  approval,
declaration or other  communication  shall or may be given to or served upon any
of the parties by any other  party,  or whenever  any of the parties  desires to
give or serve upon any other communication with respect to this Agreement,  each
such  notice,  demand,  request,   consent,   approval,   declaration  or  other
communication  shall be in writing and either  shall be delivered in person with
receipt  acknowledged  or sent by registered or certified  mail,  return receipt
requested,  postage prepaid, or by telecopy and confirmed by telecopy answerback
addressed as follows:

                  (a)  If to the Lender, at:

                       Hughes Communications Satellite Services, Inc.
                          c/o Hughes Electronics Corp.
                          7200 Hughes Terrace
                          Los Angeles, California 90045

                           Attention:  Craig R. Valiza,
                           Telecopy:   (310) 568-6051

                           with a copy to:

                        Attention: Amnon Carr, Assistant Treasurer
                           Telecopy: (310) 348-8791


                  (b)   If to the Borrower, at:

                        AMSC Subsidiary Corporation
                           10802 Parkridge Boulevard
                           Reston, Virginia 20191
                           Attention:  Treasurer
                                       General Counsel

                           Telecopy:   Treasurer:  (703) 716-6366
                                       General Counsel:  (703) 758-6134





                                       16




<PAGE>



or at such  other  address  as may be  substituted  by  notice  given as  herein
provided.  The giving of any notice required  hereunder may be waived in writing
by the party  entitled to receive such notice.  Every notice,  demand,  request,
consent, approval,  declaration or other communication hereunder shall be deemed
to have been duly  given or  served on the date on which  personally  delivered,
with receipt  acknowledged,  telecopied and confirmed by telecopy  answerback or
three (3) Business  Days after the same shall have been  deposited in the United
States  mail.  Failure  or delay in  delivering  copies of any  notice,  demand,
request,  consent,  approval,  declaration or other communication to the persons
designated  above  to  receive  copies  shall  in no way  adversely  affect  the
effectiveness of such notice, demand, request, consent, approval, declaration or
other communication.

                  10.  Severability.  Any provision of this  Agreement  which is
prohibited or unenforceable in any jurisdiction  shall, as to such jurisdiction,
be ineffective to the extent of such  prohibition  or  unenforceability  without
invalidating  the  remaining  provisions  hereof,  and any such  prohibition  or
unenforceability   in  any   jurisdiction   shall  not   invalidate   or  render
unenforceable such provision in any other jurisdiction.

                  11.  No  Waiver.  The  Lender  shall  not by any  act,  delay,
omission  or  otherwise  be deemed to have  waived any of its rights or remedies
hereunder, and no waiver shall be valid unless in writing, signed by the Lender,
and then only to the extent  therein  set  forth.  A waiver by the Lender of any
right or remedy hereunder on any one occasion shall not be construed as a bar to
any right or remedy  which the  Lender  would  otherwise  have had on any future
occasion.  No failure to exercise nor any delay in exercising on the part of the
Lender,  any right,  power or  privilege  hereunder,  shall  operate as a waiver
thereof,  nor shall any  single  or  partial  exercise  of any  right,  power or
privilege  hereunder  preclude  any  other or  future  exercise  thereof  or the
exercise of any other right, power or privilege. None of the terms or provisions
of this  Agreement  may be waived,  altered,  modified  or amended  except by an
instrument  in writing,  duly executed by the Lender and by the Borrower and the
Parent Guarantor.

                  12.  Amendments.  This Agreement,  the Term Note and the other
Loan  Documents  constitute  the  complete  agreement  between the parties  with
respect to the subject matter hereof and may not be modified, altered or amended
except by an  agreement in writing  signed by the  Borrower  and the Lender.  No
amendment  or waiver of any  provision of this  Agreement  or the Term Note,  no
consent to any departure by the Borrower  therefrom,  nor release of any Pledged
Collateral,  shall in any event be effective unless the same shall be in writing
signed by the Lender.



                                       17




<PAGE>



                  13.  Assignments; Successors and Assigns; Governing Law.

                  (a) The Borrower and the Parent Guarantor may not sell, assign
or transfer any of this  Agreement or any portion  thereof,  including,  without
limitation, its rights, title, interests,  remedies, powers and duties hereunder
or thereunder, without the prior written consent of the Lender.

                  (b) This Agreement and all obligations of the Borrower and the
Parent  Guarantor  hereunder shall be binding upon the successors and assigns of
the Borrower and the Parent Guarantor,  and shall,  together with the rights and
remedies of the Lender hereunder, inure to the benefit of the Lender, all future
holders of the Term Note and their respective  successors and assigns.  No sales
of participations,  other sales, assignments, transfers or other dispositions of
any agreement governing or instrument  evidencing the Secured Obligations or any
portion  thereof or interest  therein  shall in any manner  affect the  security
interest granted to the Lender under any Loan Document.

                  (c) This Agreement  shall be governed by, and be construed and
interpreted  in  accordance  with,  the laws of the State of New  York,  without
regard to the provisions thereof relating to conflict of laws.

                  14. Survival.  The  representations  and warranties of each of
the Parent  Guarantor  and the  Borrower  in this  Agreement  shall  survive the
execution,  delivery and acceptance hereof by the parties hereto and the closing
of the transactions described herein or re lated hereto.

                  15.  Remedies  Cumulative.  The  Lender's  rights and remedies
under this Agreement  shall be cumulative and  nonexclusive  of any other rights
and  remedies  which the Lender may have  under any other  agreement,  including
without limitation,  the Term Note or the AMSC Pledge Agreement, by operation of
law or otherwise.




                                       18




<PAGE>


                  16. WAIVER OF JURY TRIAL. EACH OF THE PARENT GUARANTOR AND THE
BORROWER  WAIVES  ALL  RIGHT TO TRIAL BY JURY IN ANY  ACTION  OR  PROCEEDING  TO
ENFORCE OR DEFEND ANY RIGHTS OR REMEDIES HEREUNDER,  UNDER THIS AGREEMENT, UNDER
THE TERM  NOTE  UNDER  THE AMSC  PLEDGE  AGREEMENT  OR  RELATING  TO EACH OF THE
FOREGOING.

                  17.  Section  Titles.  The Section  titles  contained  in this
Agreement  are and shall be without  substantive  meaning or content of any kind
whatsoever and are not a part of the agreement between the parties hereto.

                  18.  Counterparts.  This Agreement may be executed in any
number of counterparts, which shall, collectively and separately,
constitute one agreement.





                                       19




<PAGE>


                  IN WITNESS WHEREOF, each of the parties hereto has caused this
Agreement to be executed and  delivered  by its duly  authorized  officer on the
date first set forth above.

                                           AMERICAN MOBILE SATELLITE CORPORATION



                                           By:/s/Gary M. Parsons
                                              ------------------
                                           Name:  Gary Parsons
                                                  ------------
                                           Title: CEO, President
                                                  --------------


                                           AMSC SUBSIDIARY CORPORATION



                                            By:/s/Gary M. Parsons
                                               ------------------
                                            Name:  Gary Parsons
                                                   ------------
                                            Title: CEO, President
                                                   --------------


                                           HUGHES COMMUNICATIONS SATELLITE
                                           SERVICES, INC.



                                           By:/s/Amnon Carr
                                              -------------
                                           Name:   Amnon Carr
                                                   ----------
                                           Title:  Assistant Treasurer
                                                   -------------------








<PAGE>








                                                                      Schedule I

                                   TERM LOANS


<TABLE>
<CAPTION>

Date                                                    Maximum Term Loan Amount

<S>                                                           <C>
Prior to and including                                        $ 0
  January 4, 1998

January 5, 1998 to and                                        $ 1,000,000
  including January 11, 1998

January 12, 1998 to and                                       $ 2,000,000
  including January 18, 1998

January 19, 1998 to and                                       $ 3,000,000
  including January 25, 1998

January 26, 1998 to and                                       $ 4,000,000
  including February 1, 1998

February 2, 1998 to and                                       $ 8,000,000
  including February 8, 1998

February 9, 1998 and thereafter                               $10,000,000



</TABLE>


<PAGE>







                                                                       EXHIBIT A

                           AMSC SUBSIDIARY CORPORATION
                                    Term Note


$10,000,000                                                   New York, New York
                                                               December 30, 1997


                  FOR VALUE RECEIVED,  the undersigned,  a Delaware  corporation
dually  incorporated as a Virginia Public Service  corporation (the "Borrower"),
hereby PROMISES TO PAY to the order of HUGHES COMMUNICATIONS SATELLITE SERVICES,
INC., a Delaware  company (the "Lender"),  its successors or assigns,  in lawful
money of the United States of America and in immediately  available  funds,  the
amount of TEN MILLION DOLLARS  ($10,000,000)  (or, if less, the unpaid principal
amount of Loans made by Lender to the Borrower under the Loan Agreement referred
to  below)  on the  Maturity  Date and to pay  interest  from and after the date
hereof  on the  unpaid  principal  amount  hereof  at the rates and on the dates
provided in the Loan Agreement referred to below.

                  This Note is  issued  pursuant  to that  certain  Bridge  Loan
Agreement,  dated as of December 30, 1997, by and among the  Borrower,  American
Mobile  Satellite  Corporation  and Lender,  (as such  agreement may be amended,
modified or otherwise supplemented from time to time, the "Loan Agreement"), and
is  entitled to the benefit and  security  as  provided  for  therein,  to which
reference  is hereby  made for a  statement  of all of the terms and  conditions
under which the loans evidenced hereby are made. All capitalized  terms,  unless
otherwise  defined herein,  shall have the meanings ascribed to them in the Loan
Agreement.

                  If any  payment on this Note  becomes due and payable on a day
other than a Business  Day, the maturity  thereof  shall be extended to the next
succeeding  Business Day and,  with respect to payments of  principal,  interest
thereon shall be payable at the then applicable rate during such extension.

                  Upon and after the occurrence of an Event of Default,  without
demand,  notice or legal  process of any kind,  this Note may be  declared,  and
immediately shall become, or may automatically  (without any notice) become, due
and payable.


<PAGE>


                  Demand,  presentment,  protest  and notice of  nonpayment  and
protest are hereby waived by the Borrower.

                  This Note has been  delivered  and  accepted at New York,  New
York and shall be interpreted, governed by and construed in accordance with, the
laws of the State of New York.

                                            AMSC SUBSIDIARY CORPORATION



                                            By:
                                            Name:
                                            Title:










<PAGE>





                                                       Exhibit 10.64a
                                                       --------------

                                PLEDGE AGREEMENT


                  PLEDGE  AGREEMENT,  dated as of  December  30,  1997,  made by
American Mobile Satellite  Corporation,  a Delaware corporation (the "Pledgor"),
to Hughes Communications Satellite Services, Inc., a California corporation (the
"Secured Party").


                              W I T N E S S E T H:


                  WHEREAS,  each  of the  Pledgor,  as  Parent  Guarantor,  AMSC
Subsidiary Corporation, a Delaware corporation dually incorporated as a Virginia
Public Service  corporation (the "Borrower"),  and the Secured Party, as Lender,
have entered into a Bridge Loan  Agreement,  dated as of December 30, 1997 (said
Agreement,  as it may be amended or otherwise  modified from time to time, being
the "Bridge Loan Agreement" and capitalized terms not defined herein but defined
therein being used herein as therein defined);

                  WHEREAS,  the  Pledgor  is the legal and  beneficial  owner of
eighty  percent  (80%) of the issued and  outstanding  shares of common stock of
AMRC Holdings,  Inc., a Delaware  corporation  ("AMRC Holdings") as described in
Schedule I hereto (the "Pledged Shares"); and

                  WHEREAS,  it is a  condition  precedent  under the Bridge Loan
Agreement to the making of the Loan that the Pledgor  shall have made the pledge
contemplated by this Agreement.

                  NOW, THEREFORE,  in consideration of the premises and in order
to induce the Secured Party to make the Loan, the Pledgor hereby agrees with the
Secured Party as follows:

                  SECTION 1.  Pledge.  (a) The Pledgor hereby pledges
to the Secured Party, and grants to the Secured Party, a
security interest in, the following (the "Pledged Collateral"):

                         (i) all of the Pledged Shares;

                         (ii) all additional shares of stock or other securities
                    of AMRC  Holdings  from time to time acquired by the Pledgor
                    in any manner and all shares of stock or other securities of
                    AMRC Holdings held by or owned by any Person who,  after the
                    date  of  this  Agreement,  becomes,  as  a  result  of  any
                    occurrence,  a  Subsidiary  of the Pledgor  (any such shares
                    being "Additional Shares");

                         (iii) the certificates representing the shares referred
                    to in clauses (i) and (ii) above; and



<PAGE>



                         (iv)  all  dividends,   cash,   instruments  and  other
                    property or proceeds, from time to time received, receivable
                    or  otherwise  distributed  in respect of or in exchange for
                    any or all of the foregoing.

                  (b) Upon payment in full of the Secured  Obligations under the
Bridge Loan Agreement, the pledge and security interest granted pursuant to this
Section 1 shall  terminate.  Upon such  termination,  the  Secured  Party  shall
execute  and  deliver  to the  Pledgor,  at the  Pledgor's  sole  expense,  such
documents as the Pledgor shall reasonably request to evidence the termination of
such pledges or security interests or the release of all Pledged Collateral,  as
the case may be.

                  SECTION 2. Security for  Obligations.  This Agreement  secures
and the Pledged  Collateral is security for the full and prompt payment when due
(whether  at  stated  maturity,  by  acceleration  or  otherwise)  of,  and  the
performance  of, the Secured  Obligations  of the Borrower under (and as defined
in) the Bridge Loan Agreement.

                  SECTION 3. Delivery of Pledged Collateral. All certificates or
instruments representing or evidencing the Pledged Collateral shall be delivered
to and held by or on behalf of the Secured Party pursuant hereto and shall be in
suitable form for transfer by delivery, or shall be accompanied by duly executed
instruments  of  transfer  or  assignment  in blank,  all in form and  substance
satisfactory  to the Secured Party.  The Secured Party shall have the right,  at
any time in its discretion and without notice to the Pledgor,  to transfer to or
to register in its name or in the name of any of its  nominees any or all of the
Pledged Collateral;  provided,  however, that notwithstanding anything contained
herein to the  contrary,  any such  transfer  or  registration  in the name of a
nominee shall be subject to the assumption by such  transferee or nominee of the
terms and conditions of the AMRC Holdings Shareholders'  Agreement, as described
in Section 7(a)(i)(E) below. In addition, the Secured Party shall have the right
at any time to exchange  certificates or instruments  representing or evidencing
any of the Pledged  Collateral  for  certificates  or  instruments of smaller or
larger denominations.

                  SECTION 4.  Representations and Warranties.  The Pledgor makes
the following representations:

                  (a) The  Pledged  Shares  (i) have  been duly  authorized  and
validly issued;  (ii) are fully paid and  non-assessable;  and (iii)  constitute
eighty percent (80%) of the issued and outstanding shares of AMRC Holdings.

                  (b) The  Pledgor  is the  legal  and  beneficial  owner of the
Pledged  Collateral free and clear of any Lien, except for the Lien and security
interest created by this Agreement.



<PAGE>



                  (c)  The  pledge  of  the  Pledged  Shares  pursuant  to  this
Agreement  creates a valid and perfected first priority security interest in the
Pledged Collateral, securing the payment of all of the Secured Obligations.

                  (d) No consent,  authorization,  approval, or other action by,
and no notice to or filing with,  any  Governmental  Authority or third party is
required  either (i) for the pledge by the  Pledgor  of the  Pledged  Collateral
pursuant to this Agreement or for the due execution,  delivery or performance of
this Agreement by the Pledgor,  or (ii) for the exercise by the Secured Party of
the rights  provided for in this  Agreement or of the remedies in respect of the
Pledged Collateral pursuant to this Agreement,  except as may be required by the
rules and regulations of the Federal Communications  Commission (the "FCC") from
time to time in effect in connection with the disposition of, exercise of voting
rights with respect to, or transfer of control of, the Pledged Collateral, or by
laws affecting the offering and sale of securities generally, and except for any
written  consent of other  shareholders  required  under Section  2.01(a) of the
Shareholders'  Agreement,  dated as of May 16,  1997,  by and among the Pledgor,
WorldSpace, Inc. and the Parent Guarantor.

                  SECTION 5. Further  Assurances,  Etc.  (a) The Pledgor  agrees
that at any time and from time to time,  at the cost and expense of the Pledgor,
the Pledgor  will  promptly  execute and  deliver  all further  instruments  and
documents,  and take all further action, that may be necessary or desirable,  or
that the Secured Party may request, in order to perfect and protect the Lien and
security  interest  granted or purported  to be granted  hereby or to enable the
Secured  Party to exercise  and enforce its rights and remedies  hereunder  with
respect to any Pledged Collateral.

                  (b) The  Pledgor  agrees  to defend  the title to the  Pledged
Collateral  and the Lien  thereon and security  interest  therein of the Secured
Party  against the claim of any other Person and to maintain  and preserve  such
Lien and  security  interest  until  indefeasible  payment in full of all of the
Secured Obligations.

                  SECTION 6.  Voting Rights; Dividends; Etc.

                  (a) As long as no Event of Default  or event  which with lapse
of time or lack of notice  would  have  become an Event of  Default  shall  have
occurred and be continuing (or, in the case of subsection (a)(i) of this Section
6, as long as no notice  thereof  shall have been given by the Secured  Party to
the Pledgor):



<PAGE>
                         (i) The Pledgor  shall be entitled to exercise  any and
                    all voting and other  consensual  rights  pertaining  to the
                    Pledged  Collateral  or any part thereof for any purpose not
                    inconsistent  with the terms of this  Agreement or any other
                    Loan Document; provided, however, that the Pledgor shall not
                    exercise or shall refrain from exercising any such right if,
                    in the Secured Party's judgment,  exercised reasonably, such
                    action would have a material  adverse effect on the value of
                    the Pledged  Collateral or any part  thereof;  and provided,
                    further,  that the Pledgor  shall give the Secured  Party at
                    least five Business  Days'  written  notice of the manner in
                    which it intends to exercise,  or its reasons for refraining
                    from exercising, any such right.

                         (ii) The  Pledgor  shall not be  entitled to receive or
                    retain (A) any cash dividends paid in respect of the Pledged
                    Collateral,  or (B) any other  dividends  paid in respect of
                    the Pledged Collateral,  including,  without limitation, any
                    of the following:

                                    (x) dividends paid or payable in respect of,
                           and   instruments   and  other   property   received,
                           receivable or otherwise distributed in respect of, or
                           in exchange for, any Pledged
                           Collateral,

                                    (y) dividends and other  distributions  paid
                           or  payable  in  cash  in  respect  of  any   Pledged
                           Collateral  in  connection  with a  partial  or total
                           liquidation or  dissolution  or in connection  with a
                           reduction    of   capital,    capital    surplus   or
                           paid-in-surplus, and

                                    (z)  cash   paid,   payable   or   otherwise
                           distributed in redemption of, or in exchange for, any
                           Pledged Collateral,

                  all of which, together with any cash dividends received by the
                  Pledgor in violation of clause (A) of this clause (ii),  shall
                  be forthwith delivered to the Secured Party to hold as Pledged
                  Collateral and shall, if received by the Pledgor,  be received
                  in trust for the benefit of the Secured  Party,  be segregated
                  from  the  other  property  or funds  of the  Pledgor,  and be
                  forthwith delivered to the Secured Party as Pledged Collateral
                  in  the  same  form  as  so  received   (with  any   necessary
                  indorsement).

                  (b) Upon the occurrence and during the continuance of an Event
of Default:

                         (i) Upon  notice by the Secured  Party to the  Pledgor,
                    all rights of the Pledgor to  exercise  the voting and other
                    consensual  rights  which it would  otherwise be entitled to
                    exercise  pursuant to Section 6(a)(i) above shall cease, and
                    all such rights shall thereupon become vested in the Secured
                    Party who shall  thereupon  have the sole right to  exercise
                    such voting and other consensual rights.


<PAGE>




                         (ii) The  Pledgor  shall,  if  necessary  to permit the
                    Secured  Party to exercise the voting and other rights which
                    it may be entitled to exercise  pursuant to Section  6(b)(i)
                    above and to receive all dividends and  distributions  which
                    it may be entitled to receive under Section  6(b)(ii) above,
                    execute and deliver to the Secured Party,  from time to time
                    and upon written  notice of the Secured  Party,  appropriate
                    proxies,  dividend  payment orders and other  instruments as
                    the Secured  Party may  reasonably  request.  The  foregoing
                    shall  not in any way limit the  Secured  Party's  power and
                    authority granted pursuant to Section 8 hereof.

                  SECTION 7. Transfers and Other Liens;  Additional  Shares. (a)
The Pledgor agrees that it will not (i) sell or otherwise  dispose of any of the
Pledged  Collateral,  or grant any option or warrant with respect to, any of the
Pledged  Col  lateral,  other  than  those  options  which  may  be  granted  to
WorldSpace, Inc., a Maryland corporation ("WorldSpace"), pursuant to:

         (A)      the  Participation  Agreement,  dated as of March 14, 1997, by
                  and between WorldSpace,  American Mobile Radio Corporation,  a
                  Delaware corporation ("AMRC"), and Pledgor;

         (B)      the Memorandum of  Understanding,  dated as of April 15, 1997,
                  by and between WorldSpace, AMRC and Pledgor;

         (C)      the Bridge,  Additional  Amounts and  Working  Capital  Credit
                  Facility, dated as of May 16, 1997, among AMRC Holdings, AMRC,
                  Pledgor and WorldSpace;

         (D)      the Stock Subscription and Exchange Agreement, dated as of May
                  16, 1997, by and between WorldSpace,  AMRC Holdings,  AMRC and
                  Pledgor;

         (E)      the Shareholders' Agreement,  dated as of May 16, 1997, by and
                  between  AMRC  Holdings,  WorldSpace  and  Pledgor  (the "AMRC
                  Holdings Shareholders' Agreement");

         (F)      the Bridge  Option,  dated as of May __,  1997,  between  AMRC
                  Holdings and WorldSpace;

         (G)      the  Additional  Amounts  Option,  dated  as of May 16,  1997,
                  between AMRC and WorldSpace;

         (H)      the Working Capital Option,  dated as of May 16, 1997, between
                  AMRC Holdings and WorldSpace; and



<PAGE>



         (I)      the Security Agreement, dated as of May 16, 1997, between AMRC
                  Holdings and WorldSpace

         (collectively, the "Existing WorldSpace Arrangements"),


or (ii)  create or permit to exist any Lien upon or with  respect  to any of the
Pledged  Collateral,  except  for the Lien  and the  security  interest  created
pursuant to this Agreement.

                  (b) The  Pledgor  agrees  that it will (i) not vote any of the
Pledged  Shares  in  favor  of the  issuance  of any  shares  of  stock or other
securities  of AMRC Holdings in addition to or in  substitution  for the Pledged
Shares,  (A) except  with the  written  consent  of the  Secured  Party,  to the
Pledgor,  and (B) except for any shares to be issued  pursuant  to the  Existing
WorldSpace Arrangements, (ii) pledge hereunder, immediately upon its acquisition
(directly or  indirectly)  thereof,  any and all  Additional  Shares,  and (iii)
promptly  (and in any event  within two  Business  Days)  deliver to the Secured
Party a Pledge  Amendment,  duly  executed  by the Pledgor or any other owner of
Additional  Shares,  in substantially  the form of Schedule II hereto (a "Pledge
Amendment"), in respect of the Additional Shares, together with all certificates
or  instruments  representing  or evidencing  the same.  The Pledgor  hereby (i)
authorizes  the Secured  Party to attach each  Pledge  Amendment  to this Pledge
Agreement, (ii) agrees that all Additional Shares listed on any Pledge Amendment
delivered  to the Secured  Party  shall for all  purposes  hereunder  constitute
Pledged  Shares,  and (iii) is deemed to have made,  with respect to any and all
Additional   Shares   pledged  by  the   Pledgor,   upon  such   delivery,   the
representations  and  warranties  contained  in Section 4 hereof with respect to
such Pledged Collateral.

                  SECTION 8. Secured Party Appointed Attorney-in-Fact and Proxy.
The Pledgor hereby  irrevocably  constitutes  and appoints the Secured Party and
any officer or agent thereof,  with full power of substitution,  as its true and
lawful  attorney-in-fact  and proxy with full irrevocable power and authority in
the place and stead of the  Pledgor and in the name of the Pledgor or in its own
name, from time to time in the Secured Party's discretion, exercised reasonably,
for the purpose of carrying out the terms of this Agreement, to take any and all
appropriate  action  and to  execute  and  deliver  any  and all  documents  and
instruments  which  the  Secured  Party  may  deem  necessary  or  advisable  to
accomplish the purposes of this Agreement,  including,  without  limitation,  to
receive,  indorse  and  collect  all  instruments  made  payable to the  Pledgor
representing  any  dividend or other  distribution  or payment in respect of the
Pledged Collateral or any part thereof,  to give full discharge for the same and
to vote or grant any  consent in respect of the  Pledged  Shares  authorized  by
Section 6(b) hereof.  The Pledgor hereby  ratifies,  to the extent  permitted by
law, all that any said attorney  shall lawfully do or cause to be done by virtue
hereof.  This power,  being coupled with an interest,  is irrevocable  until the
Secured Obligations are paid in full.


<PAGE>




                  SECTION 9. Secured Party May Perform.  If the Pledgor fails to
perform any agreement contained herein, the Secured Party may itself perform, or
cause  performance  of, such  agreement,  and the expenses of the Secured  Party
incurred in connection  therewith  shall be payable by the Pledgor under Section
12 hereof and constitute Secured Obligations secured hereby.

                  SECTION 10. Reasonable Care. The Secured Party shall be deemed
to have exercised reasonable care in the custody and preservation of the Pledged
Collateral  in its  possession if the Pledged  Collateral is accorded  treatment
substantially  equal to that which the Secured Party accords its own property of
a similar  nature,  it being  understood  that the  Secured  Party  shall not be
responsible  for (i)  ascertaining  or  taking  action  with  respect  to calls,
conversions,  exchanges,  maturities,  tenders or other matters  relative to any
Pledged  Collateral,  whether or not the Secured  Party has or is deemed to have
knowledge of any such  matter,  or (ii) taking any  necessary  steps to preserve
rights against any Person with respect to any Pledged Collateral.

                  SECTION 11.  Remedies  upon Event of Default.  If any Event of
Default shall have occurred and be continuing, the Secured Party may, subject to
the rules and regulations of the FCC from time to time in effect, if applicable,
exercise any or all of the followings  rights,  remedies and recourses which may
now or hereafter exist in equity or at law:

                  (a) The Secured  Party may  exercise in respect of the Pledged
Collateral,  in addition to other  rights and  remedies  provided  for herein or
otherwise  available to it, all the rights and remedies of a secured party after
default under the Uniform  Commercial Code in effect in the State of New York at
that time,  and the Secured Party may also,  without  notice except as specified
below, sell the Pledged Collateral or any part thereof in one or more parcels at
public or private sale, at any exchange,  broker's board or at any office of the
Secured Party or elsewhere, for cash, on credit or for future delivery, and upon
such other terms as the Secured Party may deem commercially  reasonable;  except
that,  notwithstanding  anything contained herein to the contrary,  the right of
the Secured  Party to sell and assign or  otherwise  transfer any of the Pledged
Collateral  shall be subject,  at all times,  to the terms and conditions of the
AMRC Holdings  Shareholders'  Agreement.  The Pledgor agrees that, to the extent
notice of sale  shall be  required  by law,  at least  ten  days'  notice to the
Pledgor  of the time and place of any public  sale or the time  after  which any
private sale is to be made shall constitute reasonable notification. The Secured
Party shall not be obligated to make any sale of Pledged  Collateral  regardless
of notice of sale having been given. The Secured Party may adjourn any public or


<PAGE>



private  sale from  time to time by  announcement  at the time and  place  fixed
therefor,  and such sale may,  without further  notice,  be made at the time and
place to which it was so adjourned. The Pledgor hereby waives any claims against
the  Secured  Party  arising  by  reason of the fact that the price at which any
Pledged  Collateral  may have been sold at such a private sale was less than the
price which might have been obtained at a public sale, even if the Secured Party
accepts the first offer  received and does not offer such Pledged  Collateral to
more than one offeree.

                  (b) The  Secured  Party may elect to obtain (at the  Pledgor's
expense) the advice of any independent  nationally-known investment banking firm
with respect to the method and manner of sale or other disposition of any of the
Pledged  Collateral,   the  best  price  reasonably  obtainable  therefor,   the
consideration of cash and/or credit terms, or any other details  concerning such
sale or disposition.

                  (c) If the Secured Party shall determine to exercise its right
to sell all or any of the Pledged  Collateral  pursuant to this  Section 11, the
Pledgor agrees that, upon request of the Secured Party, the Pledgor will, at its
own cost and expense:

                         (i) execute and  deliver,  and use its best  efforts to
                    cause the issuer of the Pledged Shares and its directors and
                    officers to execute and deliver,  all such  instruments  and
                    documents,  and do or cause to be done all such  other  acts
                    and things,  as may be  necessary  or, in the opinion of the
                    Secured  Party,  necessary  or  advisable  to register  such
                    Pledged Shares under the provisions of the Securities Act of
                    1933, as from time to time amended (the  "Securities  Act"),
                    and to cause the registration  statement relating thereto to
                    become  effective and to remain effective for such period as
                    prospectuses  are  required by law to be  furnished,  and to
                    make  all  amendments  and  supplements  thereto  and to the
                    related  prospectus  which,  in the  opinion of the  Secured
                    Party,  are necessary or advisable,  all in conformity  with
                    the  requirements  of the  Securities  Act and the rules and
                    regulations  of  the  Securities  and  Exchange   Commission
                    ("SEC") applicable thereto;

                         (ii)  use its  best  efforts  to  qualify  the  Pledged
                    Collateral under the state securities or "Blue Sky" laws and
                    to obtain all necessary  governmental approvals for the sale
                    of the  Pledged  Collateral,  as  requested  by the  Secured
                    Party;

                         (iii) make available to its security  holders,  as soon
                    as practicable,  an earning statement which will satisfy the
                    provisions of section 11(a) of the Securities Act; and


<PAGE>



                         (iv) do or cause to be done  all  such  other  acts and
                    things as may be  necessary to make such sale of the Pledged
                    Collateral  or any part  thereof  valid and  binding  and in
                    compliance with applicable law.

The Pledgor further acknowledges the impossibility of ascertaining the amount of
damages which would be suffered by the Secured Party by reason of the failure by
the Pledgor to perform any of the  covenants  contained  in this Section 11 and,
consequently,  agrees  that,  if the  Pledgor  shall fail to perform any of such
covenants,  it shall pay, as liquidated damages and not as a penalty,  an amount
equal to the value of the Pledged Collateral on the date the Secured Party shall
demand compliance with this Section.

                  (d)  The   Pledgor   recognizes   that,   by   reason  of  the
aforementioned requirements and certain prohibitions contained in the Securities
Act and applicable  state securities laws, the Secured Party may, at its option,
elect not to require  the  Pledgor to  register  all or any part of the  Pledged
Collateral  and may therefore be  compelled,  with respect to any sale of all or
any part of the Pledged Collateral, to limit purchasers to those who will agree,
among other  things,  to acquire  such  securities  for their own  account,  for
investment,  and not with a view to the  distribution  or  resale  thereof.  The
Pledgor  acknowledges  and  agrees  that any such sale may  result in prices and
other  terms less  favorable  to the seller than if such sale were a public sale
without such restrictions and,  notwithstanding such circumstances,  agrees that
any such sale  shall be deemed  to have been made in a  commercially  reasonable
manner.  The Secured Party shall be under no obligation to delay the sale of any
of the Pledged Collateral for the period of time necessary to permit the Pledgor
to register such  securities for public sale under the Securities  Act, or under
applicable state securities laws, even if the Pledgor would agree to do so.

                  (e) If the Secured  Party  determines to exercise its right to
sell any or all of the Pledged  Collateral,  upon written  request,  the Pledgor
shall,  from time to time,  furnish to the Secured Party all such information as
the  Secured  Party may request in order to  determine  the number of shares and
other  instruments  included in the Pledged  Collateral which may be sold by the
Secured Party as exempt  transactions  under the Securities Act and rules of the
SEC thereunder, as the same are from time to time in effect.

                  (f) Any cash held by the Secured  Party as Pledged  Collateral
and all cash  proceeds  received by the Secured Party in respect of any sale of,
collection  from,  or other  realiza  tion  upon all or any part of the  Pledged
Collateral shall be applied by the Secured Party:



<PAGE>


                  First, to the payment of the costs and expenses of such  sale,
including, without limitation,  reasonable expenses of the Secured Party and its
agents  including  the fees  and  expenses  of its  counsel,  and all  expenses,
liabilities  and advances  made or incurred by the Secured  Party in  connection
therewith or pursuant to Section 9 hereof;

                  Next, toward  the  payment in full of the Secured Obligations;
and

                  Finally,   after  payment  in  full  of  all  of  the  Secured
Obligations,  to the payment to the Pledgor, or its successors or assigns, or to
whomsoever may be lawfully  entitled to receive the same as a court of competent
jurisdiction may direct.

                  SECTION 12. Expenses.  The Pledgor will upon demand pay to the
Secured Party the amount of any and all reasonable expenses,  including, without
limitation,  the reasonable fees and expenses of the Secured Party's counsel and
of any experts and agents,  which the Secured Party may incur in connection with
(i) the  administration of this Agreement,  (ii) the custody or preservation of,
sale of,  collection  from,  or other  realiza  tion  upon,  any of the  Pledged
Collateral,  (iii) the exercise or enforcement of any of the rights and remedies
hereunder of the Secured Party, or (iv) the failure by the Pledgor to perform or
observe any of the provisions hereof.

                  SECTION 13.  Security  Interest  Absolute.   All rights of the
Secured  Party and security  interests  hereunder,  and all  obligations  of the
Pledgor hereunder, shall be absolute and unconditional irrespective of:

                         (i)  any  lack of  validity  or  enforceability  of any
                    provision  of the Bridge  Loan  Agreement  or any other Loan
                    Document  or any  other  agreement  or  instrument  relating
                    thereto;

                         (ii) any change in the time, manner or place of payment
                    of, or in any other term of, or any  increase  in the amount
                    of,  all or any of the  Secured  Obligations,  or any  other
                    amendment  or waiver of any term of, or any  consent  to any
                    departure from any requirement of, the Bridge Loan Agreement
                    or any other Loan Document;

                         (iii) any exchange,  release or  non-perfection  of any
                    Lien on any other collateral, or any release or amendment or
                    waiver  of any  term  of any  guaranty  of,  or  consent  to
                    departure  from any  requirement  of any guaranty of, all or
                    any of the Secured Obligations; or

                         (iv)  any  other  circumstance  which  might  otherwise
                    constitute  a defense  available  to, or a  discharge  of, a
                    borrower  or a pledgor  (other  than  payment in full of the
                    Secured Obligations).


<PAGE>



                  SECTION 14.  Amendments,  Etc. No  amendment  or waiver of any
provision of this Agreement nor consent to any departure by the Pledgor herefrom
shall in any event be effective unless the same shall be in writing, approved by
the  Secured  Party and signed by the  Secured  Party,  and then such  waiver or
consent  shall be effective  only in the specific  instance and for the specific
purpose for which given.

                  SECTION  15.  Addresses  for  Notices.  All  notices and other
communications  provided for hereunder shall be in writing  (including  telecopy
communication)  and mailed,  telecopied  (with a subsequent  hard copy mailed or
delivered by hand,  Federal Express or any other nationally  recognized  courier
service)  or  delivered  by  hand,  Federal  Express  or  any  other  nationally
recognized courier service, if to the Pledgor or the Secured Party, addressed to
the Pledgor or the Secured  Party at its  address  specified  in the Bridge Loan
Agreement, or, as to each party, at such other address as shall be designated by
such party in a written notice to each other party complying as to delivery with
the terms of this Section. All such notices and other communications shall, when
mailed,  telecopied  or  delivered,  be effective  when  deposited in the mails,
telecopied with confirmation of receipt,  or delivered by hand,  Federal Express
or such other courier service to the addressee or its agent, respectively.

                  SECTION 16. Continuing Security Interest; Transfer of Notes or
Obligations.  This Pledge Agreement shall create a continuing  security interest
in the Pledged  Collateral  and shall (i) remain in full force and effect  until
indefeasible  payment in full of the Secured  Obligations,  (ii) be binding upon
the Pledgor,  its  successors  and assigns,  and (iii) inure,  together with the
rights and  remedies of the Secured  Party  hereunder,  to the benefit of and be
enforceable by the Secured Party and its respective successors,  transferees and
assigns,  subject  to and upon the  terms and  conditions  set forth in the AMRC
Shareholders'  Agreement.  Upon the payment in full of the Secured  Obligations,
the Pledgor shall be entitled to the return,  promptly as practicable,  upon its
request and at its expense,  of such of the Pledged Collateral as shall not have
been sold or otherwise applied pursuant to the terms hereof.

                  SECTION 17. Governing Law; Severability; Terms. This Agreement
shall be governed by, and be construed and  interpreted in accordance  with, the
law of the  State of New York  (but  without  giving  effect  to  principles  of
conflicts of laws). Wherever possible, each provision of this Agreement shall be
interpreted  in such manner as to be effective and valid under  applicable  law,
but if any provision of this  Agreement  shall be prohibited by or invalid under
applicable law, such provision  shall be ineffective  only to the extent of such
prohibition or invalidity and without  invalidating the remaining  provisions of
this Agreement. Unless otherwise defined herein or in the Bridge Loan Agreement,
terms  defined in Article 9 of the Uniform  Commercial  Code as in effect in the
State of New York are used herein as therein defined.


<PAGE>


                  SECTION 18. Submission to Jurisdiction;  Jury Trial; Judgment.
(a) Any  legal  action or  proceeding  with  respect  to this  Agreement  or any
document related hereto may be brought in the courts of the State of New York or
the United  States of America for the  southern  district  of New York,  and, by
execution and delivery of this Agreement,  the Pledgor hereby accepts for itself
and in respect of its property, generally and unconditionally,  the jurisdiction
of the aforesaid courts.  The Pledgor hereby  irrevocably  waives any objection,
including,  without limitation, any objection to the laying of venue or based on
the grounds of forum non conveniens, which the Pledgor may now or hereafter have
to  the  bringing  of  any  such  action  or  proceeding   in  such   respective
jurisdictions  and consents to the granting of such legal or equitable relief as
is deemed appropriate by the court.

                  (b) To the  extent  that  the  Pledgor  has or  hereafter  may
acquire any immunity  from  jurisdiction  of any court or from any legal process
(whether through service or notice, attachment prior to judgment,  attachment in
aid of  execution,  execution  or  otherwise)  with  respect  to  itself  or its
property,  the Pledgor hereby irrevocably waives to the fullest extent permitted
by law such immunity in respect of its obligations  under this Agreement and the
other Loan Documents.  The Pledgor waives to the fullest extent permitted by law
any right it may have to trial by jury in  respect of any  litigation  based on,
arising out of,  under or in  connection  with this  Agreement or any other Loan
Document,  or any  course of  conduct,  course  of  dealing,  verbal or  written
statement or other action of any Loan Party or the Secured Party.


                  SECTION 19.  Section Titles.  The Section titles contained  in
this  Agreement are and shall be without  substantive  meaning or content of any
kind whatsoever and are not part of this Agreement.


<PAGE>




                  IN WITNESS  WHEREOF,  the Pledgor has caused this Agreement to
be duly executed and delivered by its duly authorized  officer on the date first
above written.

                                                     AMERICAN MOBILE SATELLITE
                                                     CORPORATION


                                                     By:/s/Gary M. Parsons
                                                        ------------------
                                                         Name:  Gary M. Parsons
                                                         Title: CEO, President


Accepted and Acknowledged:


HUGHES COMMUNICATIONS SATELLITE
SERVICES, INC.


By:/s/Amnon Carr
    Name:  Amnon Carr
    Title: Assistant Treasurer



<PAGE>




                         SCHEDULE I TO PLEDGE AGREEMENT


         Attached to and forming a part of that certain Pledge Agreement,  dated
as of December 30, 1997,  by American  Mobile  Satellite  Corporation  to Hughes
Communications Satellite Services, Inc.


                                     Stock
                    Class           Certificate                       Number of
Stock Issuer       of Stock          No(s).           Par Value         Shares


AMRC Holdings,      Common            001               $0.10             100
Inc.








<PAGE>


                         SCHEDULE II TO PLEDGE AGREEMENT

                                PLEDGE AMENDMENT



                           This Pledge  Amendment,  dated ,     ,  is  delivered
                                                            ----   
         pursuant to Section 7 of the Pledge  Agreement  referred to below.  The
         undersigned hereby agrees that this Pledge Amendment may be attached to
         the Pledge  Agreement,  dated as of  December  30,  1997,  between  the
         undersigned  and Hughes  Communications  Satellite  Services,  Inc., as
         Secured Party referred to therein and that the Additional Shares listed
         on this  Pledge  Amendment  shall  be and  become  part of the  Pledged
         Collateral  referred to in the Pledge  Agreement  and shall  secure all
         Secured Obligations of the undersigned. The terms defined in the Pledge
         Agreement  or Bridge  Loan  Agreement  are being used herein as therein
         defined.

                                                 [AMERICAN MOBILE SATELLITE
                                                 CORPORATION][              ]


                                                  By:
                                                     Name:
                                                     Title:



                                        Stock
                       Class         Certificate                     Number of
Stock Issuer          of Stock          No(s).      Par Value          Shares







                                                            Exhibit 10.64b
                                                            --------------

                           AMSC SUBSIDIARY CORPORATION
                                    Term Note


$10,000,000                                                   New York, New York
                                                               December 30, 1997


                  FOR VALUE RECEIVED,  the undersigned,  a Delaware  corporation
dually  incorporated as a Virginia Public Service  corporation (the "Borrower"),
hereby PROMISES TO PAY to the order of HUGHES COMMUNICATIONS SATELLITE SERVICES,
INC., a Delaware  company (the "Lender"),  its successors or assigns,  in lawful
money of the United States of America and in immediately  available  funds,  the
amount of TEN MILLION DOLLARS  ($10,000,000)  (or, if less, the unpaid principal
amount of Loans made by Lender to the Borrower under the Loan Agreement referred
to  below)  on the  Maturity  Date and to pay  interest  from and after the date
hereof  on the  unpaid  principal  amount  hereof  at the rates and on the dates
provided in the Loan Agreement referred to below.

                  This Note is  issued  pursuant  to that  certain  Bridge  Loan
Agreement,  dated as of December 30, 1997, by and among the  Borrower,  American
Mobile  Satellite  Corporation  and Lender,  (as such  agreement may be amended,
modified or otherwise supplemented from time to time, the "Loan Agreement"), and
is  entitled to the benefit and  security  as  provided  for  therein,  to which
reference  is hereby  made for a  statement  of all of the terms and  conditions
under which the loans evidenced hereby are made. All capitalized  terms,  unless
otherwise  defined herein,  shall have the meanings ascribed to them in the Loan
Agreement.

                  If any  payment on this Note  becomes due and payable on a day
other than a Business  Day, the maturity  thereof  shall be extended to the next
succeeding  Business Day and,  with respect to payments of  principal,  interest
thereon shall be payable at the then applicable rate during such extension.

                  Upon and after the occurrence of an Event of Default,  without
demand,  notice or legal  process of any kind,  this Note may be  declared,  and
immediately shall become, or may automatically  (without any notice) become, due
and payable.

                  Demand,  presentment,  protest  and notice of  nonpayment  and
protest are hereby waived by the Borrower.




<PAGE>
                  This Note has been  delivered  and  accepted at New York,  New
York and shall be interpreted, governed by and construed in accordance with, the
laws of the State of New York.

                                            AMSC SUBSIDIARY CORPORATION




                                            By:/s/Gary M. Parsons
                                               Name:  Gary M. Parsons
                                               Title: CEO, President








<PAGE>





                                                                EXHIBIT 10.65
                                                                -------------


                            STOCK PURCHASE AGREEMENT

                             FOR THE ACQUISITION OF

                        MOTOROLA ARDIS ACQUISITION, INC.

                                       AND

                              MOTOROLA ARDIS, INC.

                                       BY

                         AMSC ACQUISITION COMPANY, INC.

                            A WHOLLY-OWNED SUBSIDIARY

                                       OF

                      AMERICAN MOBILE SATELLITE CORPORATION






                          Dated as of December 31, 1997









<PAGE>



                                TABLE OF CONTENTS

                                                                            Page

ARTICLE 1.  DEFINITIONS..................................................      1

ARTICLE 2.  MERGER, PURCHASE AND SALE OF SHARES..........................     13

        Section 2.1               Merger, Purchase and Sale
                                  of Shares       .......................     13
        Section 2.2               MAI Purchase Price and MAA
                                  Purchase Price.........................     14
        Section 2.3               Purchase Price Adjustments.............     14
        Section 2.4               Post-Closing Purchase Price
                                  Adjustment.............................     15
        Section 2.5               Closing Place, Date and Time...........     17
        Section 2.6               FCC Authorization and Final Order......     17
        Section 2.7               Deliveries at Closing..................     18
        Section 2.8               Deliveries Post-Closing................     20

ARTICLE 3.  REPRESENTATIONS AND WARRANTIES
                OF SELLER................................................     20

        Section 3.1               Organization and Good Standing.........     20
        Section 3.2               Authority; No Required Consents
                                  or Governmental Authorizations;
                                  No Breach of Statute or Contract;
                                  Enforceability.........................     21
        Section 3.3               Ownership of Shares....................     23
        Section 3.4               Capitalization of MAA, MAI
                                  and the Subsidiaries...................     23
        Section 3.5               Corporate Records......................     23
        Section 3.6               Employee Benefit Plans.................     24
        Section 3.7               Broker's or Finder's Fees..............     26
        Section 3.8               Financial Statements...................     26
        Section 3.9               Accounts Receivable....................     27
        Section 3.10              Absence of Undisclosed
                                  Liabilities............................     27
        Section 3.11              Existing Condition.....................     28
        Section 3.12              Title to Properties; Leasehold
                                  Interests..............................     30
        Section 3.13              Condition of Tangible Assets...........     30
        Section 3.14              Books of Account.......................     31
        Section 3.15              Litigation.............................     31
        Section 3.16              Compliance with Law....................     31
        Section 3.17              Environmental Matters..................     32
        Section 3.18              Insurance..............................     32
        Section 3.19              Contracts and Commitments..............     33
        Section 3.20              Additional Information.................     34
        Section 3.21              Intellectual Property..................     35
        Section 3.22              No Third Party Options.................     37
        Section 3.23              Tariffs; FCC Licenses;
                                  Non-FCC Authorizations.................     37
        Section 3.24              Officer and Employee Compensation......     39
        Section 3.25              Indebtedness...........................     39
        Section 3.26              Access; Sophistication; etc............     39
        Section 3.27              Investment Representation..............     40


ARTICLE 4.  REPRESENTATIONS AND WARRANTIES OF
                AMSC AND PURCHASER.......................................     41

        Section 4.1               Organization and Good Standing.........     41
        Section 4.2               Authority; No Required Consents
                                  or Governmental Authorizations
                                  or Breach of Statute or
                                  Contract; Enforceability...............     41
        Section 4.3               Broker's or Finder's Fees..............     43
        Section 4.4               Access; Sophistication; etc............     43
        Section 4.5               Investment Representation..............     43
        Section 4.6               SEC Filings; Financial
                                  Statements.............................     44
        Section 4.7               Absence of Certain Changes.............     45
        Section 4.8               Absence of Undisclosed
                                  Liabilities............................     45
        Section 4.9               Litigation.............................     45


ARTICLE 5.  CERTAIN AGREEMENTS...........................................     46

        Section 5.1               Conduct of the Business................     46
        Section 5.2               Access to Information..................     49
        Section 5.3               Efforts; Further Assurances;...........     49
                                  Permits
        Section 5.4               Books and Records......................     50
        Section 5.5               Governmental Regulatory
                                  Approvals..............................     50
        Section 5.6               FCC Consent............................     51
        Section 5.7               HSR Act Review.........................     51
        Section 5.8               Registration Rights....................     51
        Section 5.9               Lock-up................................     51
        Section 5.10              Nonsolicitation........................     52
        Section 5.11              IBM Contract Renewal...................     52
        Section 5.12              UPS Contract...........................     52
        Section 5.13              Escrow Agreement.......................     52
        Section 5.14              Employee Transition....................     53
        Section 5.15              Updated Disclosure Schedule............     53
        Section 5.16              Nextel Proceeds........................     53
        Section 5.17              Non-Vendor Intercompany Financing
                                  Arrangements...........................     53
        Section 5.18              Intercompany Agreements................     54



ARTICLE 6.  CONDITIONS TO CLOSING........................................     54

        Section 6.1               Conditions to Obligation of
                                  Purchaser..............................     54
        Section 6.2               Conditions to Obligations of
                                  Seller..        .....................       56

ARTICLE 7.  INDEMNIFICATION..............................................     58

        Section 7.1               Indemnification by Seller..............     58
        Section 7.2               Indemnification by AMSC................     59
        Section 7.3               Limitations on Indemnification for
                                  Breaches of Representations and
                                  Warranties.............................     59
        Section 7.4               Survival of Representations and
                                  Warranties.............................     60
        Section 7.5               Method of Asserting Claims.............     60
        Section 7.6               Method of Payment......................     62
        Section 7.7               Limitation of Recourse.................     63
        Section 7.8               Acknowledgment by Seller, Purchaser
                                  and AMSC        .......................     63


ARTICLE 8.  TAX MATTERS..................................................     64

        Section 8.1               Seller's Tax Representations
                                  and Warranties.........................     64
        Section 8.2               AMSC's Tax Representations
                                  and Warranties.........................     66
        Section 8.3               Tax Returns, Audits, Contests, Etc.;
                                  Tax Cooperation; Tax Sharing
                                  Agreements; Tax Records................     68
        Section 8.4               Asset Purchase Treatment
                                  for MAI Shares.........................     72
        Section 8.5               Tax-Free Reorganization
                                  Treatment..............................     76
        Section 8.6               Transfer Taxes.........................     76
        Section 8.7               General Tax Indemnifications...........     76
        Section 8.8               Exclusive Remedy for Taxes.............     81
        Section 8.9               Survival and Purchase Price
                                  Adjustment.............................     81

ARTICLE 9.  TERMINATION OF AGREEMENT; PAYMENT OF
                EXPENSES; WAIVER OF CONDITIONS...........................     82

        Section 9.1               Termination Pre-Agreement..............     82
        Section 9.2               Termination Post-Closing...............     83
        Section 9.3               Payment of Expenses; Waiver of
                                  Conditions.............................     84

ARTICLE 10.  MISCELLANEOUS...............................................     84

Section 10.1                      Amendments.............................     84
Section 10.2                      Further Instruments and
                                  Assurances.............................     84
Section 10.3                      Public Announcements...................     85
Section 10.4                      Governing Law..........................     85
Section 10.5                      Notices         .......................     85
Section 10.6                      Assignment and Binding Effect..........     86
Section 10.7                      Entire Agreement.......................     86
Section 10.8                      Severability...........................     87
Section 10.9                      Counterparts...........................     87
Section 10.10                     No Third Party Beneficiaries...........     87
Section 10.11                     Delays or Omissions....................     87
Section 10.12                     Construction...........................     87
Section 10.13                     Knowledge Standard.....................     88
Section 10.14                     Expenses        .......................     88






<PAGE>









                                    EXHIBITS

Exhibit

A                                 AMSC Warrants

B                                 Registration Rights Agreement





                                 



<PAGE>


                            STOCK PURCHASE AGREEMENT


             THIS STOCK PURCHASE  AGREEMENT  (this  "Agreement")  is dated as of
December  31, 1997 and is entered into by and among  MOTOROLA,  INC., a Delaware
corporation ("Seller"),  MOTOROLA ARDIS ACQUISITION, INC. a Delaware corporation
("MAA"),  and MOTOROLA ARDIS, INC. a Delaware  corporation ("MAI"), and American
Mobile  Satellite  Corporation,   a  Delaware  corporation  ("AMSC"),  and  AMSC
Acquisition Company, Inc., a Delaware corporation ("Purchaser").


                             ARTICLE 1. DEFINITIONS.

            Section 1.1  Definitions.
                         -----------

            "Acquisition Proposal" has the meaning set forth in Section 5.9.

            "Adverse Legal Opinion" has the meaning set forth in Section 2.6(a).

            "Affiliate" shall mean with respect to any Person, any other Person
that is  directly  or  indirectly  controlling,  controlled  by or under  common
control  with such  Person or  entity or any of its  subsidiaries,  and the term
"control"  (including the terms "controlled by" and "under common control with")
means having, directly or indirectly, the power to direct or cause the direction
of the management and policies of a Person,  whether through ownership of voting
securities or by contract or otherwise

            "Affiliated Group" shall  mean  an "affiliated group" as defined in
Section 1504(a) of the Code.

            "Agreement" has the meaning set forth in the introductory paragraph
hereof.

            "AMSC Common  Stock" shall mean the common  stock,  par value $0.01
per share, of AMSC.

            "AMSC Group" shall mean any Affiliated  Group  including  AMSC, any
successor  thereof or, if such Affiliated  Group shall cease to exist,  AMSC and
any successors thereto.

            "AMSC  Shareholder  Approval" has  the meaning set forth in Section
2.7(a)(iv).

            "AMSC  Warrants"  shall  mean  warrants  issued  by AMSC to  Seller
substantially in the form attached hereto as Exhibit A.

            "ARDIS" means ARDIS Company.

            "ARDIS Balance Sheet" shall mean the unaudited consolidated balance
sheet of ARDIS Holding as of September 30, 1997.

            "ARDIS Balance Sheet Date" has the meaning set forth in Section 3.8.

            "ARDIS Holding" means ARDIS Holding Company.

             "Benefit  Plan"  shall  mean any plan,  agreement,  arrangement  or
commitment  which  is  an  employment  or  consulting  agreement,  executive  or
incentive   compensation  plan,  bonus  plan,  retention  bonus  plan,  deferred
compensation agreement,  employee pension, profit sharing, savings or retirement
plan,  employee  stock  option  or stock  purchase  plan,  group  life,  health,
disability,  sick pay or accident  insurance  or other  employee  benefit  plan,
agreement, arrangement or commitment,  including, without limitation, severance,
holiday,  vacation,  Christmas or other bonus plans (including,  but not limited
to, employee benefit plans, as defined in Section 3(3) of ERISA), maintained for
the benefit of any employee or director or former employee or former director of
MAA, MAI or any of the Subsidiaries whether or not maintained by MAA, MAI or any
of the Subsidiaries or with respect to which MAA, MAI or any of the Subsidiaries
makes or has any obligation to make contributions.

             "Books and Records" shall mean all of MAA's,  MAI's and each of the
Subsidiaries'  customer or  subscriber  lists and records,  accounts and billing
records  (including a copy of the detailed  general ledger and the summary trial
balances,  where available),  detailed  continuing  property records,  equipment
records,  plans,  blueprints,   specifications,   designs,  drawings,   surveys,
engineering  reports,   personnel  records  (where  applicable)  and  all  other
documents,  computer data and records  (including  records and files on computer
disks or stored electronically) relating to the Subsidiaries.

             "Business Day" means any day other than  Saturday,  Sunday or a day
that  constitutes  a legal  holiday in the State of Illinois or the  District of
Columbia.

             "CERCLA"  shall  mean  the  Comprehensive  Environmental  Response,
Compensation and Liability Act of 1980, as amended.

             "Claim Notice" has the meaning set forth in Section 7.5(a).

             "Closing" has the meaning set forth in Section 2.5.

             "Closing Cash Payment" has the meaning set forth in Section 2.3.

             "Closing Date" has the meaning set forth in Section 2.5.

             "Closing  Financial   Statements"  shall  mean  (i)  the  unaudited
consolidated  income statement and statement of cash flows for ARDIS Holding for
the period from January 1, 1998 through the Closing Date and (ii) the  unaudited
consolidated balance sheet for ARDIS Holding effective as of the Closing Date.

             "Closing Stock Payment" has the meaning set forth in Section 2.3.

             "Closing Working Capital" has the meaning set forth in Section 2.3.

             "Code" shall mean the Internal Revenue Code of 1986, as amended.

             "Collateral   Agreements"   shall  mean  the  Registration   Rights
Agreement,  the Escrow Agreement and all such other  agreements  entered into by
the parties hereto in connection with the transactions contemplated hereby.

             "Common  Stock"  shall  mean the common  stock,  par value $.01 per
share, of MAA and the common stock, par value $.01 per share, of MAI.

             "Companies" shall mean MAA, MAI and the Subsidiaries.

             "Company" shall mean any one of the Companies.

             "Consideration Shares" has the meaning set forth in Section 2.2.

             "Control"  shall  mean  the  power to  direct  the  management  and
policies of a Person,  directly or indirectly,  whether through the ownership of
voting  securities,  by contract or otherwise;  and the terms  "controlling" and
"controlled" shall have meanings correlative to the foregoing.

             "Cumulative  Temporary  Differences" means the differences  between
the bases in assets  and  liabilities  for  Financial  Statement  and income Tax
purposes that will result in the recognition of different  amounts of income and
expense for Financial Statement and income Tax purposes in future periods.

             "Disclosure Schedule" shall mean the Disclosure Schedule, including
the Introduction thereto,  delivered simultaneously herewith by Seller and dated
as of even date herewith.

             "Environmental  Conditions" shall mean any and all acts, omissions,
events, circumstances, and conditions,  including any pollution,  contamination,
degradation,  damage,  or injury  caused by,  related to, or arising  from or in
connection with the generation,  use, handling,  treatment,  storage,  disposal,
discharge, emission or release of Hazardous Materials.

             "Environmental  Laws"  shall  mean  all  federal,  state,  local or
municipal laws, rules,  regulations,  statutes, and ordinances and orders of any
Governmental Entity relating to (a) the control of any potential  pollutant,  or
protection  of the air,  water or land,  (b)  solid,  gaseous  or  liquid  waste
generation,  handling, treatment,  storage, disposal or transportation,  and (c)
exposure  to  hazardous,  toxic  or  other  substances  alleged  to be  harmful.
"Environmental  Laws" shall  include the Clean Air Act, the Clean Water Act, the
Resource   Conservation   and  Recovery  Act,  the  Superfund   Amendments   and
Reauthorization  Act, the Toxic Substances  Control Act, the Safe Drinking Water
Act, and the CERCLA, and shall also include all state, local and municipal laws,
rules,  regulations,  statutes,  ordinances  and orders dealing with the subject
matter of the above listed federal  statutes or promulgated by any  governmental
or  quasi-governmental  agency  thereunder in order to carry out the purposes of
any federal, state, local or municipal law.

             "Environmental  Liabilities"  shall  mean any and all  liabilities,
responsibilities,  claims,  suits, losses,  costs (including remedial,  removal,
response,  abatement,  clean-up,  investigative  and/or monitoring costs and any
other related costs and expenses),  other causes of action  recognized now or at
any later time, damages,  settlements,  expenses, charges,  assessments,  liens,
penalties,  fines, pre-judgment and post-judgment interest,  attorneys' fees and
other legal costs  incurred or imposed  (a)  pursuant to any  agreement,  order,
notice  of   responsibility,   directive   (including   directive   embodied  in
Environmental  Laws),  injunction,  judgment  or  similar  documents  (including
settlements)  arising out of, in connection with, or under  Environmental  Laws,
(b) pursuant to any claim by a Governmental  Entity or other Person for personal
injury, property damage, damage to natural resources, remediation, or payment or
reimbursement of response costs incurred or expended by such Governmental Entity
or Person pursuant to common law or statute, or (c) as a result of Environmental
Conditions.

             "ERISA" shall mean the Employee  Retirement  Income Security Act of
1974, as amended.

             "ERISA Affiliate" shall mean any person, firm or entity (whether or
not  incorporated)  which, by reason of its relationship with MAA, MAI or any of
the  Subsidiaries,  is required  to be  aggregated  with MAA,  MAI or any of the
Subsidiaries  under Sections 414(b),  (c) or (m) of the Code or which,  together
with MAA,  MAI or any of the  Subsidiaries,  is a member of a  controlled  group
within the meaning of Section 4001(a) of ERISA.

             "Escrow  Agent" shall mean a national  banking  association,  trust
company or similar entity mutually acceptable to the parties.

             "Escrow  Agreement"  shall  mean an escrow  agreement  by and among
Seller,  Purchaser, AMSC and the Escrow Agent containing such terms as are usual
and  customary  for  similar  documents  used  in  similar  circumstances,   and
containing specifically the following terms:

               (a) Upon consummation of the financing contemplated under Section
               6.1(l)  hereof,  Purchaser  shall deposit all of the net proceeds
               thereof with the Escrow Agent (the "Escrowed Funds");

               (b) Prior to the Closing,  the Escrowed Funds shall be maintained
               for the benefit of Purchaser,  with the interest accruing thereon
               until the Closing Date being allocated to Purchaser;

               (c) Upon  Closing,  (i) the MAI  Purchase  Price  portion  of the
               Escrowed  Funds  shall be  maintained  for the benefit of Seller,
               with the  interest  accruing on such amount  beginning  as of the
               Closing  Date being  allocated  to Seller (the  "Seller  Escrowed
               Funds"),  and (ii) the remainder of the Escrowed Funds (including
               any interest  accrued on the Escrowed  Funds prior to the Closing
               Date) shall be maintained for the benefit of Purchaser,  with the
               interest  accruing on such  remaining  amount of  Escrowed  Funds
               beginning  as of the Closing  Date being  allocated  to Purchaser
               (the "Purchaser Escrowed Funds");

               (d) Upon issuance of a Final Order from the FCC granting  consent
               with respect to the FCC Authorization,  the Seller Escrowed Funds
               shall be  released  to Seller and the  Purchaser  Escrowed  Funds
               shall be released to Purchaser;

               (e) In the event of a termination of this  Agreement  pursuant to
               Article 9, all of the  Escrowed  Funds  (including  all  interest
               accrued thereon) shall be released to Purchaser.

             "Estimated Working Capital" has  the meaning  set forth in  Section
2.3.

             "FCC" shall mean the Federal Communications Commission.

             "FCC Authorization" has the meaning set forth in Section 2.6(a).

             "FCC Consents" has the meaning set forth in Section 5.6.

             "FCC Licenses"  shall mean all licenses,  certificates,  permits or
other  authorizations  granted to MAA, MAI or any of the Subsidiaries by the FCC
that are used in the conduct of the business of MAA, MAI or the Subsidiaries.

             "Final Order" shall mean an action or decision as to which:  (1) no
request for a stay is pending, no stay is in effect, and any deadline for filing
such request that may be designated by statute or regulation has passed;  (2) no
petition for rehearing or  reconsideration  or application for review is pending
and the time for filing any such petition or application has passed; (3) the FCC
(or  comparable  body  exercising  jurisdiction)  does not have  the  action  or
decision  under  reconsideration  on its own motion and the  specified  time for
initiating such  reconsideration  has passed; and (4) no appeal is pending or in
effect and any  deadline  for filing any such appeal that may be  designated  by
statute or rule has passed.

             "Final Payment" has the meaning set forth in Section 2.4.

             "Financial  Statements" shall mean the consolidated  balance sheets
of ARDIS  Holding as of December 31, 1997,  December 31, 1996,  and December 31,
1995, the related  statements of income and retained  earnings and notes thereto
for the 12-month periods then ended,  examined by Price Waterhouse,  LLP (or, in
the case of those for 1997,  KPMG Peat Marwick),  independent  certified  public
accountants, and the unaudited consolidated balance sheet of ARDIS Holding as of
September  30,  1997 and the  related  consolidated  statements  of  income  and
retained earnings for the 9-month period then ended.

             "GAAP"  shall  mean   generally   accepted  accounting  principles,
consistently applied.

             "Governmental  Entity"  shall  mean any public  body or  authority,
including courts of competent jurisdiction, domestic or foreign.

             "Hazardous  Materials"  shall mean any (a)  petroleum  or petroleum
products,  (b) hazardous  substances as defined by ss. 101(14) of CERCLA and (c)
any other  chemical,  substance or waste that is  regulated by any  Governmental
Entity under any Environmental Law.

             "HSR Act" shall mean the Hart-Scott-Rodino  Antitrust  Improvements
Act of 1976, as amended.

             "Indemnification  Threshold  Amount"  has  the meaning set forth in
Section 7.3(a).

             "Indemnitee" has the meaning set forth in Section 7.5.

             "Indemnitor" has the meaning set forth in Section 7.5.

             "Intellectual  Property" shall mean all of the following throughout
the universe:  (i) patents and patent applications and all forms and equivalents
thereof,  including  divisions,  continuations,  continuations-in-part,  utility
patents, design patents, extensions, reissued and reexamined patents, patents of
addition,  confirmation patents, importation patents,  registration patents, and
inventor's  certificates;  (ii)  rights to file  patent  applications  and other
interests in inventions and discoveries,  whether reduced to practice or not, on
which no patent application has been filed; (iii) copyrights and all related and
equivalent rights, including copyright registrations, applications for copyright
registration,  moral rights, and neighboring  rights;  (iv) common law and other
trademarks,  trade names,  trade dress, and service marks, and registrations and
applications for registration  thereof;  (v) rights in industrial designs,  mask
works, and registrations and applications for registration  thereof;  (vi) trade
secrets;  (vii)  methods,  processes,   computer  software,  designs,  drawings,
laboratory  notebooks,  technical data, research and development data, know-how,
market reports, consumer investigations,  product surveys, distribution methods,
and customer  lists;  (viii)  licenses to or under and shop rights in any of the
foregoing; and (ix) all other proprietary information;  provided,  however, that
the term  "Intellectual  Property"  shall not  include any  generally  available
"off-the-shelf"  software purchased for use in the day-to-day  operations of the
Companies.

             "Interim  Financial  Statement"  shall mean the ARDIS Balance Sheet
and the related  consolidated  statements  of income and  retained  earnings and
notes thereto for the 9-month period then ended.

             "Lien" shall mean, with respect to any asset,  any mortgage,  lien,
pledge, charge,  security interest or encumbrance of any kind in respect of such
asset.

             "Litigation"  shall mean,  with respect to any Person,  any action,
claim,  demand,  suit,  proceeding,  citation,  summons,  subpoena,  inquiry  or
investigation of any nature, civil, criminal, regulatory or otherwise, in law or
in equity,  pending or threatened against, by or affecting such Person or any of
its properties or assets, by or before any court, tribunal,  arbitrator or other
Governmental Entity.

             "Lock-up Period" has the meaning set forth in Section 5.9.

             "Losses" has the meaning set forth in Section 7.1.

             "MAA Purchase Price" has the meaning set forth in Section 2.2(B).

             "MAA Shares"  shall mean all of the shares of capital  stock of MAA
outstanding immediately prior to the Closing.

             "MAI Purchase Price" has the meaning set forth in Section 2.2(A).

             "MAI Shares"  shall mean all of the shares of capital  stock of MAI
outstanding immediately prior to the Closing.

             "Management  Employee"  shall mean the key managers of ARDIS, to be
designated by Seller prior to the time  Purchaser's  obligations to Seller arise
under the last sentence of Section 5.14 herein, not to exceed 12 employees.

             "Market  Value" shall mean the average of the closing prices of the
AMSC Common Stock on the Nasdaq Stock Market (National Market System) for the 20
trading days immediately preceding the date of such calculation.

             "Material  Adverse Effect" shall mean a material  adverse effect on
MAA, MAI and the Subsidiaries, taken as a whole.

             "Material Adverse Change"  shall mean a material  adverse change in
the  business,  operation,   assets,  properties,  or  condition  (financial  or
otherwise) of MAI, MAA and the Subsidiaries, taken as a whole.

             "Merger" has the meaning set forth in Section 2.1(a).

             "Merger  Sub"  shall  mean  a   wholly-owned   subsidiary  of  AMSC
established for the purpose of consummating the Merger with MAA.

             "Multiemployer  Plan"  shall  mean  each  Benefit  Plan  that  is a
multiemployer plan, as defined in Section 3(37) of ERISA.

             "NASD" has the meaning set forth in Section 2.7(a)(iv).

             "Non-FCC  Authorizations"  shall mean all  licenses,  certificates,
permits,  franchises,  or other authorizations (other than FCC Licenses) granted
to MAA, MAI or any of the Subsidiaries by Governmental Entities that are used in
or relate to the conduct of the business of MAA, MAI or any of the Subsidiaries,
including,  without limitation,  those from any state public service commission,
public utility commission or similar state agency.

             "Nonsolicitation Period" has the meaning set forth in Section 5.10.

             "Notice Period" has the meaning set forth in Section 7.5(b).

             "Other Subsidiaries" shall mean the Subsidiaries other than ARDIS.

             "Other Tax Costs" means liabilities,  costs and expenses (including
reasonable  expenses  of  investigation  and  reasonable   attorneys'  fees  and
expenses)  arising  out  of or  incidental  to  the  imposition,  assessment  or
assertion of Taxes;  provided,  however,  that  expenses for  investigation  and
attorneys'  fees incurred prior to the time the  indemnified  party notifies the
indemnifying party of its claim for  indemnification  shall not constitute Other
Tax Costs if the indemnifying  party acknowledges in writing within fifteen (15)
days of the time of such  notice  that it assumes  full and  complete  financial
responsibility for the issue or issues for which  indemnification is sought; and
further  provided,  that Other Tax Costs  shall not  include  any  expenses  for
investigation or attorney fees incurred subsequent to the notification  referred
to in the preceding clause of this definition  provided the  indemnifying  party
timely makes the written acknowledgment described in such clause and is actively
handling the matter with respect to which indemnification is acknowledged.

             "Permitted Lien" shall mean (a) tax Liens with respect to taxes not
yet due and payable;  or which are being  contested in good faith by appropriate
proceedings and for which appropriate reserves (as determined in accordance with
and to the extent  required by GAAP) have been  established  on the books of any
Subsidiary with respect thereto; (b) deposits or pledges made in connection with
or to secure payment of utilities or similar  services,  workers'  compensation,
unemployment  insurance,  old age pensions or other social security obligations;
(c) interests or title of a lessor under any lease, mechanics', materialmen's or
contractors'  Liens or any similar Lien or  restriction  for amounts not yet due
and  payable;  (d)  easements,  rights-of-way,  restrictions  and other  similar
charges and encumbrances not materially interfering with the ordinary conduct of
the business of the  Subsidiaries  or detracting from the value of the assets of
its Subsidiaries;  (e) other Liens, imperfections in title, charges,  easements,
restrictions and encumbrances;  which,  individually or in the aggregate, do not
detract from the value in any material respect, or materially interfere with the
present use of the property subject thereto or affected thereby.

             "Person" shall mean an individual, a corporation,  a partnership, a
limited  liability  company,  an  association,   a  trust  or  other  entity  or
organization,  including a government or political  subdivision  or an agency or
instrumentality thereof.

             "Purchaser" has the meaning set forth in the introductory paragraph
hereof.

             "Real Property" has the meaning set forth in Section 3.20(a).

             "Realty  Rights"  shall mean those certain  easements,  privileges,
right-of-way agreements, surface use rights, servitudes, and other real property
interests  necessary for access to or which are ancillary or  appurtenant to the
use and  enjoyment  of other Real  Property or the  operation of the business of
MAA, MAI or the Subsidiaries.

             "Reconciliation Adjustment in Favor  of Purchaser"  has the meaning
set forth in Section 2.4.

             "Reconciliation Adjustment in Favor of Seller" has  the meaning set
forth in Section 2.4.

             "Registration  Rights Agreement"  has  the  meaning  set  forth  in
Section 5.8.

             "Regulatory Approvals" has the meaning set forth in Section 5.5.

             "Required Consents" has the meaning set forth in Section 3.2(b).

             "Securities Act" shall mean the Securities Act of 1933, as amended.

             "Seller"  has the meaning  set forth in the  introductory paragraph
hereof.

             "Seller Group" shall mean any Affiliated  Group including Seller or
any successor thereof or, if such Affiliated Group shall cease to exist,  Seller
and any successors thereto.

             "Severance Package" has the meaning set forth in Section 5.14.

             "Shares" shall mean all of the MAA Shares and MAI Shares.

             "Short Taxable Year" shall mean any Taxable Year that either begins
or ends on the Closing Date or begins on the date immediately  after the Closing
Date, in either case by reason of the purchase and sale of the Shares.

             "Split  Period" means a taxable period that begins on or before the
Closing Date and ends after the Closing Date.

             "State"  means  any state of the  United  States  of  America,  the
District of Columbia, or a local jurisdiction thereof.

             "Subsidiaries" shall mean ARDIS, ARDIS Holding,  Radio Data Network
Holding  Corporation,  and  each  corporation,  limited  liability  company  and
partnership identified as such in Section 3.1 of the Disclosure Schedule.

             "Tax"  or  "Taxes"  shall  mean  all  taxes,  however  denominated,
including  any  interest,  penalties  or  additions  to tax or other  additional
amounts  that may become  payable in respect  thereof,  imposed by any  federal,
State, local or foreign government or any agency or political subdivision of any
such government,  which taxes shall include,  without limiting the generality of
the  foregoing,  all net or gross  income  taxes,  payroll  and  employee  taxes
(including  withholding,  payroll and  employment  taxes required to be withheld
with  respect to income  paid to  employees),  withholding  taxes,  unemployment
insurance  taxes,   social  security  (or  similar)  taxes,   disability  taxes,
registration  taxes, sales and use taxes,  excise taxes,  franchise taxes, gross
receipts  taxes,  occupation  taxes,  premium  taxes,  windfall  profits  taxes,
environmental  taxes (including taxes under Code Section 59A), real and personal
property taxes, ad valorem taxes, stamp taxes, value added taxes, alternative or
add-on minimum taxes, transfer taxes, profits taxes, licenses,  estimated taxes,
severance taxes,  duties (custom and others),  workers'  compensation taxes, and
other taxes, customs,  duties, fees, assessments,  charges or obligations of the
same or of a similar nature,  whether  arising  before,  on or after the Closing
Date.

             "Tax  Returns"  shall  mean  all  returns,  declarations,  reports,
estimates,  and information  statements and returns relating to Taxes, including
but not limited to, original returns and filings,  amended  returns,  claims for
refunds, and information returns, and any schedules or attachments to any of the
foregoing.

             "Taxable  Year"  shall mean any taxable  year or any other  taxable
period  (including  any Short Taxable Year) with respect to which any Tax may be
imposed under any applicable statute, rule or regulation.

             "Threshold  Amount" shall mean an amount  resulting from an adverse
effect on the financial  condition,  assets or results of operations of MAA, MAI
or any of the Subsidiaries exceeding $50,000.

             "UPS Contract" has the meaning set forth in Section 5.12.

             "Working  Capital  Schedule"  has  the meaning set forth in Section
2.4(a).

                 ARTICLE 2. MERGER, PURCHASE AND SALE OF SHARES.

             Section 2.1   Merger, Purchase and Sale of Shares.   On the Closing
                           -----------------------------------
Date, on the terms and subject to the conditions hereinafter set forth:

                     (a)  AMSC shall cause Merger Sub to be merged with and into
MAA (the "Merger")  such that (i) each issued and  outstanding  share of capital
stock of  Merger Sub prior to the Merger shall be converted  into one MAA Share,
and (ii) any MAA Shares  issued and  outstanding  prior to the Merger  shall  be
converted into the right to receive the MAA  Purchase  Price to be  delivered in
exchange  therefor, such  that following the Merger, MAA shall be a wholly-owned
subsidiary of AMSC. The certificate of incorporation of Merger Sub, as in effect
on  the  date of  the  Merger  shall be the certificate of incorporation of MAA.
Immediately  following  the Merger, AMSC shall transfer all of the MAA Shares to
Purchaser.

                      (b)  Seller shall sell, assign,  transfer  and  deliver to
Purchaser, and Purchaser shall purchase, all of the MAI Shares free and clear of
all  Liens,  subject to release by the Escrow Agent of the MAI Purchase Price to
Seller, pursuant to the terms of the Escrow Agreement.

             Section 2.2 MAI Purchase Price and MAA Purchase Price. The purchase
                         -----------------------------------------
prices to be paid by AMSC and  Purchaser  for the MAI  Shares and the MAA Shares
shall  be paid  on the  Closing  Date as  follows:  (A) for the MAI  Shares,  by
depositing  with  the  Escrow  Agent  Fifty  Million  Dollars  ($50,000,000)  in
immediately  available funds, subject to adjustment pursuant to Sections 2.3 and
2.4 below (the "MAI Purchase Price"), payable by the Escrow Agent to Seller upon
receipt  by the  parties of a Final  Order from the FCC with  respect to the FCC
Authorization;  and (B) with respect to the MAA Shares acquired  pursuant to the
terms of Section 2.1(a),  by AMSC delivering to Seller  6,549,217 shares of AMSC
Common Stock (the  "Consideration  Shares") having,  in the aggregate,  a Market
Value as of the date hereof of Fifty Million Dollars  ($50,000,000),  subject to
adjustment pursuant to Sections 2.3 and 2.4 below (the "MAA Purchase Price"), to
Seller;  provided,  however, that the total number of Consideration Shares shall
not exceed 19.95% of the total number of shares of AMSC Common Stock outstanding
as of the Closing Date (including the Consideration  Shares), and, in such case,
AMSC shall also  deliver to Seller,  AMSC  Warrants to  purchase  that number of
shares of AMSC Common  Stock equal to the  difference  between (i) the number of
Consideration Shares which would be delivered but for this proviso and (ii) that
number of shares  equal to 19.95% of the total  number of shares of AMSC  Common
Stock outstanding as of the Closing Date.

             Section 2.3 Purchase Price Adjustments.  The MAI Purchase Price and
                         --------------------------
the MAA Purchase Price shall each be decreased by 50% of the negative difference
between the Closing Working  Capital and  $7,300,000.  Seller shall estimate the
Closing  Working  Capital in good faith (the  "Estimated  Working  Capital") and
deliver  such  estimate to Buyer not less than five  Business  Days prior to the
Closing Date. At Closing,  (i) the cash payment of the MAI Purchase  Price shall
be  $50,000,000  minus 50% of the  negative  difference  between  the  Estimated
Working Capital and $7,300,000 (the "Closing Cash Payment"), and (ii) the shares
of AMSC Common Stock  delivered  in payment of the MAA  Purchase  Price shall be
6,549,217 minus such number of shares having,  in the aggregate,  a Market Value
as of the  date  hereof  equal to 50% of the  negative  difference  between  the
Estimated  Working  Capital and $7,300,000  (the "Closing Stock  Payment").  For
purposes of this Agreement,  the term "Closing  Working  Capital" shall mean the
lesser of $7,300,000 and the actual working  capital of ARDIS, on a consolidated
basis,  as of the Closing Date determined from the books and records of ARDIS in
accordance  with past  practice and, to the extent not  inconsistent  therewith,
GAAP;  provided,  however,  that in no event shall the  proceeds  referenced  in
Section  5.16  hereof be  included in the  calculation  of the  Closing  Working
Capital.

             Section 2.4  Post-Closing Purchase Price Adjustment.
                          --------------------------------------

                      (a)  Not  more  than  60 days after the Closing, Purchaser
shall  prepare and deliver to Seller a schedule (the "Working Capital Schedule")
showing (i) the calculation of the actual Closing Working Capital of ARDIS; (ii)
the amount, if any, by which the  Closing  Working Capital exceeds the Estimated
Working  Capital (a "Reconciliation  Adjustment in  Favor of Seller"); and (iii)
the  amount, if  any, by  which  the Estimated  Working Capital is less than the
Closing Working Capital (a "Reconciliation Adjustment in Favor of Purchaser").

                      (b)  The proposed actual Closing Working Capital shown  in
the  Working  Capital  Schedule  shall become final and binding upon the parties
unless, within 30 days of delivery of the Working Capital Schedule, Seller shall
notify  Purchaser  of  its  objection  thereto.  If within 30 days following the
receipt of  such  notice  by  Seller any of such differences shall not have been
resolved, such  unresolved  issues  shall be referred to a nationally recognized
firm  of  independent certified  public  accountants, mutually acceptable to the
parties, for resolution, whose opinion thereon and the resulting  actual Closing
Working Capital shall be final, binding and not subject to any appeal.  The fees
and expenses of  such public accounting firm shall be paid one-half by Purchaser
and one-half by Seller.

                      (c)  On the applicable date referred to in Section 2.4(d),
(i) if there is a Reconciliation  Adjustment in Favor of Seller, Purchaser shall
(x) pay to Seller a cash amount equal to 50% of the Reconciliation Adjustment in
Favor of Seller  and (y)  deliver to the Seller a  certificate  evidencing  such
number of shares of AMSC Common Stock having,  in  aggregate,  a Market Value on
the  Closing  Date  equal to 50% of the  Reconciliation  Adjustment  in Favor of
Seller; and (ii) if there is a Reconciliation  Adjustment in Favor of Purchaser,
Seller  shall  (i)  pay  to  Purchaser  a  cash  amount  equal  to  50%  of  the
Reconciliation Adjustment in Favor of Purchaser and (y) deliver to the Purchaser
a stock certificate endorsed in blank such number of shares of AMSC Common Stock
having,  in  aggregate,  a Market  Value on the Closing Date equal to 50% of the
Reconciliation Adjustment in Favor of Purchaser. Any such payment is hereinafter
referred to as a "Final  Payment."  In the event that the Escrow Agent holds any
cash at the time of the  Final  Payment,  such  payment  to the  Seller  or such
payment by the Seller, as applicable,  shall instead be made to or by the Escrow
Agent.  Notwithstanding the foregoing,  in the event that any issuance to Seller
of shares of AMSC Common Stock under this Section 2.4 would, when taken together
with the  issuance to Seller of shares of AMSC Common  Stock under  Section 2.2,
cause the  number of such  shares  issued to Seller in the  aggregate  to exceed
19.95% of the total number of shares of AMSC Common Stock  outstanding as of the
date of the proposed issuance of shares under this Section 2.4(c) (including the
shares to be so issued),  AMSC shall deliver to Seller AMSC Warrants to purchase
that number of shares of AMSC Common Stock equal to the  difference  between (i)
the number of total shares which would be delivered  pursuant to Section 2.2 and
this  Section 2.4 but for this  sentence and (ii) that number of shares equal to
19.95% of the total number of shares of AMSC Common Stock  outstanding as of the
Closing Date.

                      (d)  Any Final Payment shall be made as follows:   (i) the
cash portion of any Final Payment shall be made by wire transfer of  immediately
available  funds within 5 Business  Days after its  determination  in accordance
with this  Section  2.4, to an account  specified  by the party to receive  such
Final Payment;  and (ii) the portion of any Final Payment payable in AMSC Common
Stock shall be made by transferring the stock  certificate(s)  representing such
shares  (and,  if  applicable,  stock  powers  executed  in blank),  within five
Business Days after its  determination  in accordance  with this Section 2.4, to
the party to receive such Final Payment. All such shares shall be delivered free
and clear of any Liens.

             Section  2.5  Closing  Place,  Date and Time.  The  closing  of the
                           ------------------------------
purchase and sale of the Shares (the "Closing")  shall take place at the offices
of Arnold & Porter,  555 12th Street,  N.W.,  Washington,  D.C. 20004 or at such
other place as Seller and  Purchaser may agree,  upon the effective  date of the
FCC Authorization,  or if Seller and Purchaser otherwise agree, then the Closing
shall take place at such later time and date as may be  mutually  agreed upon in
writing by the Seller and Purchaser.  All  transactions  shall be deemed to take
effect  at close of  business,  local  time,  on the  effective  date of the FCC
Authorization  or such other  time and date as may be  mutually  agreed  upon by
Seller  and  Purchaser  (such  time and date or such  other  time and date being
referred to herein as the "Closing Date").

             Section 2.6  FCC Authorization and Final Order.
                          ---------------------------------

                      (a)  FCC Authorization. Upon grant of a consent by the FCC
                           -----------------
sufficient  to  authorize  transfer  of the  Shares to  Purchaser  and to permit
Purchaser to operate the  businesses  of ARDIS and the Other  Subsidiaries  (the
"FCC  Authorization"),  and  satisfaction  or  waiver  of  the  representations,
warranties  and  covenants  herein,  the  parties  shall hold the Closing on the
Closing Date;  provided,  however,  that in the event either Seller or Purchaser
obtains an opinion of legal counsel, in substance and in form, and from counsel,
reasonably  satisfactory  to the  other  party,  that  there  exists a  material
likelihood  that the FCC will issue an adverse  Final Order with  respect to the
FCC Authorization (an "Adverse Legal Opinion"), the Closing shall not take place
until receipt of a Final Order of the FCC.

                      (b)  Favorable  Final Order.  Upon  receipt by the parties
                           ----------------------
of a  Final  Order  from  the  FCC  granting  consent  with  respect  to the FCC
Authorization,  the MAI Purchase  Price shall be released by the Escrow Agent to
the Seller in accordance with the terms of the Escrow Agreement.


             Section 2.7 Deliveries at the Closing.
                         -------------------------

                      (a) At the Closing,  Purchaser  and AMSC shall deliver the
following:

                              (i)   to the Escrow Agent, the MAI  Purchase Price
in immediately available funds, pursuant to the terms of the Escrow Agreement;

                              (ii)  to   the  Seller, the  MAA  Purchase  Price,
represented  by one or more  certificates  evidencing  AMSC Common Stock and, if
applicable, AMSC Warrants;

                              (iii) to  Seller, certified  copies of resolutions
duly  adopted  by  AMSC  and  Purchaser  constituting  all  necessary  corporate
authorization  for the  consummation  by AMSC and Purchaser of the  transactions
contemplated by this Agreement;

                              (iv)  to  Seller,  certified   copies  of  meeting
minutes  and  resolutions duly  adopted by the shareholders of AMSC Common Stock
approving  the  transactions  contemplated herein, as and to the extent required
under the Rules of the National Association of Securities Dealers, Inc. ("NASD")
(the "AMSC Shareholder Approval");

                              (v)   to  Seller,  the  certificate  required  by 
Section 6.2(d);

                              (vi)  to  Seller,  certificates  of incumbency for
all  relevant  officers  or  directors  of  AMSC and  Purchaser  executing  this
Agreement and any other documents pursuant to this Agreement;

                              (vii) to Seller, an opinion or opinions of counsel
to  AMSC and  Purchaser in form and substance reasonably satisfactory, including
opinions  with  respect  to  the  due organization and good standing of AMSC and
Purchaser, due  authorization of  AMSC and  Purchaser  to consummate and perform
their respective obligations under the  Agreement and Collateral Agreements, and
the due authorization and valid issuance of the AMSC Common Stock to Seller;

                              (viii) to Seller, an executed  Registration Rights
Agreement; and

                              (ix) to Seller, such other documents, instruments,
certificates  and  writings as  reasonably  may be  requested by Seller at least
three Business Days prior to the Closing.

                      (b) At the Closing, Seller shall deliver the following:

                              (i)  to  the  Purchaser,  the  stock  certificates
representing  all of the  Shares,  endorsed  in  blank  or  accompanied  by duly
executed instruments of transfer;

                              (ii)  to  AMSC  and  Purchaser,  the  certificates
required by Section 6.1(d);

                              (iii)  to  AMSC and Purchaser, certified copies of
the  certificate of  incorporation  and  by-laws  or  comparable  organizational
documents of MAA, MAI and each of the Subsidiaries and evidence of good standing
of each in its respective jurisdiction of incorporation and in each jurisdiction
where each is qualified to transact business as a foreign corporation;

                              (iv) to  AMSC  and  Purchaser, the  written
resignations  effective as of the Closing Date of all  directors and officers of
MAA, MAI and each of the Subsidiaries;

                              (v)  to  AMSC  and  Purchaser, the  minute  books,
corporate seals and stock ledger, or analogous  documents,  of MAA, MAI and each
of the Subsidiaries together with certificates evidencing all of the outstanding
shares of stock, or other comparable evidence of ownership  interest,  issued by
each of the Subsidiaries;

                              (vi) to AMSC and Purchaser, an opinion or opinions
of counsel to Seller in form and substance  reasonably  satisfactory,  including
opinions with respect to the due organization and good standing of Seller,  MAA,
MAI and the Subsidiaries, due authorization of Seller, MAI and MAA to consummate
and perform their  respective  obligations  under the  Agreement and  Collateral
Agreements,  and the due  authorization and valid issuance of the MAA Shares and
MAI Shares to Seller;

                              (vii) to AMSC and Purchaser, such other documents,
instruments, certificates and writings as reasonably may be requested by AMSC or
Purchaser at least three Business Days prior to the Closing.

             Section 2.8  Deliveries Post-Closing.  Within  15  Business Days of
                          -----------------------
the Closing  Date,  Seller  shall  deliver to  Purchaser  the Closing  Financial
Statements.



                    ARTICLE 3. REPRESENTATIONS AND WARRANTIES
                               OF SELLER

             Seller hereby  represents  and warrants as follows to Purchaser and
AMSC:

             Section 3.1  Organization and Good Standing.
                          ------------------------------

                    (a)  MAA,   MAI  and  each  of  the  Subsidiaries  are  duly
organized,  validly  existing  and in good  standing  under  the  laws of  their
respective  jurisdictions  of  organization  and each has the full  corporate or
partnership power to conduct its business as presently  conducted and to own and
operate the assets and  properties  now owned and operated by it. Section 3.1(a)
of the Disclosure  Schedule sets forth the full name of each of the Subsidiaries
and the state of organization of MAA, MAI and each of the  Subsidiaries and each
other  jurisdiction  in which MAA,  MAI or the  Subsidiaries  is qualified to do
business.  Except as set forth in Section 3.1(a) of the Disclosure Schedule, MAA
and MAI and each of the  Subsidiaries is duly qualified to do business and is in
good standing in each  jurisdiction  in which  qualification  is required as set
forth in Section 3.1(a) of the Disclosure  Schedule except, in each case, to the
extent that the failure to be so qualified is not reasonably  expected to have a
Material Adverse Effect.

                    (b)  Neither  MAA nor MAI has any  subsidiaries  or owns any
shares of any  corporation  or has any ownership or other  investment  interest,
either of record, beneficially,  or equitably, in any association,  partnership,
joint  venture or other  legal  entity  other than the 50%  general  partnership
interest each of MAA and MAI owns in ARDIS  Holding.  ARDIS Holding does not own
any  subsidiaries  or own any  shares of any  corporation  and does not have any
ownership  or other  investment  interest,  either of record,  beneficially,  or
equitably, in any association,  partnership, joint venture or other legal entity
other than its  ownership  of all of the issued and  outstanding  stock of Radio
Data  Network  Holding  Corporation  and its  ownership of all of the issued and
outstanding  general  partnership  interest in ARDIS which is not owned by Radio
Data Network Holding  Corporation.  Radio Data Network Holding  Corporation does
not own any  subsidiaries or own any shares of any corporation and does not have
any ownership or other investment interest, either of record,  beneficially,  or
equitably, in any association,  partnership, joint venture or other legal entity
other  than  its  ownership  of  all  of  the  issued  and  outstanding  general
partnership  interest in ARDIS which is not owned by ARDIS  Holding.  ARDIS does
not own any  subsidiaries or own any shares of any corporation and does not have
any ownership or other investment interest, either of record,  beneficially,  or
equitably, in any association, partnership, joint venture or other legal entity.

                    (c)  Section  3.1(c) of the  Disclosure  Schedule  lists the
directors  and  officers of MAA,  MAI and each of the  Subsidiaries.  Seller has
caused to be delivered to Purchaser true and complete  copies of the certificate
of  incorporation  and  bylaws  of MAA and MAI,  the  comparable  organizational
documents  of each of the  Subsidiaries,  and, to the extent that they relate to
the period from January 1, 1995 to the date  hereof,  the records of meetings of
their respective stockholders, members or partners, as the case may be, board of
directors, managers and any committees of their respective board of directors or
managers,  and all of the stock  record  books for all  periods  of MAA and MAI.
Neither MAA, MAI nor any of the Subsidiaries is in default under or in violation
of any  provision of its  certificate  of  incorporation,  bylaws or  comparable
organizational documents.

             Section  3.2  Authority;   No  Required  Consents  or  Governmental
                           -----------------------------------------------------
Authorizations; No Breach of Statute or Contract; Enforceability.
- ----------------------------------------------------------------

                    (a)  Seller,  MAA and MAI each has the full power and lawful
authority to execute and deliver this  Agreement and all  Collateral  Agreements
related  hereto and to  consummate  and  perform the  transactions  contemplated
hereby in the  manner  herein  provided.  The  execution  and  delivery  of this
Agreement and all Collateral  Agreements  related hereto by Seller,  MAA and MAI
and the consummation and performance by Seller,  MAA and MAI of the transactions
contemplated  hereby in the manner  herein  provided  have been duly and validly
authorized by all necessary corporate action.

                    (b) Except as set forth in Section  3.2(b) of the Disclosure
Schedule (each such item being a "Required Consent"),  and except for approvals,
consents or  authorizations  of, or filings with or notices to any  governmental
agency or body or any other third party that may be required in connection  with
the  issuance of AMSC Common  Stock or AMSC  Warrants  as  contemplated  hereby,
neither the execution and delivery by Seller,  MAA and MAI of this  Agreement or
all Collateral Agreements related hereto nor the consummation and performance by
Seller, MAA and MAI of the transactions contemplated hereby in the manner herein
provided (i) requires the approval,  consent or authorization  of, or any filing
with or notice to, any federal,  state,  local or other  governmental  agency or
body  or  any  other  third   party,   other  than  (A)   approvals,   consents,
authorizations,  filings or notices of a character such that a failure to obtain
them  would,  reasonably  be  expected  to have a  Material  Adverse  Effect  or
otherwise hinder the consummation of the  transactions  contemplated  hereby and
(B)  approvals,  consents,  authorizations,  filings or notices  which have been
obtained,  made or given, or (ii) conflicts with or will result in an uncured or
unwaived breach or violation of any term or provision of,  constitutes a default
under  or will  cause  the  acceleration  of any  payments  pursuant  to (A) the
certificates of incorporation, charters or By-laws, or comparable organizational
documents of MAA, MAI or any of the Subsidiaries,  (B) any indenture,  mortgage,
deed  of  trust,  lease,  note or  note  agreement  or any  other  agreement  or
instrument to which Seller, MAA, MAI or any of the Subsidiaries is a party or by
which  Seller,  MAA,  MAI or any of the  Subsidiaries  or any of their assets or
properties is bound, (C) any governmental  license,  franchise,  permit or other
authorization  held by Seller,  MAA, MAI or any of the  Subsidiaries  or (D) any
law, judgment, order, writ, injunction, decree, award, rule or regulation of any
court,  arbitrator or governmental agency or body applicable to Seller, MAA, MAI
or any of the Subsidiaries the breach or violation of which would,  singly or in
the  aggregate,  reasonably  be  expected to have a Material  Adverse  Effect or
otherwise prevent the consummation of the transactions contemplated hereby.

                    (c)  This   Agreement   constitutes,   and  all   Collateral

Agreements  related  hereto will be, when  executed and  delivered by Purchaser,
assuming the  enforceability  of this Agreement and such  Collateral  Agreements
upon Purchaser,  valid and binding  obligations of Seller, MAA and MAI, and will
be  enforceable  against  Seller,  MAA and MAI in  accordance  with their terms,
subject to applicable bankruptcy,  insolvency,  moratorium or other similar laws
affecting the rights of creditors generally.

             Section 3.3  Ownership of Shares.  The Shares are  owned  by Seller
                          -------------------
beneficially and of record, free and clear of all Liens.


             Section 3.4  Capitalization of MAA, MAI and the  Subsidiaries.  The
                          ------------------------------------------------
authorized  capital stock of MAA consists of 1,000 shares of Common Stock, 1,000
of  which  shares  are  issued  and are  outstanding  on the  date  hereof.  The
authorized  capital stock of MAI consists of 1,000 shares of Common Stock, 1,000
of which shares are issued and are  outstanding  on the date hereof.  All of the
Shares have been duly authorized,  are validly issued and  outstanding,  and are
fully paid and nonassessable. They are owned beneficially and of record as shown
in Section 3.4 of the Disclosure  Schedule.  There are no preemptive rights with
respect  to any of the  Shares.  The  authorized  capital  stock  of each of the
corporate Subsidiaries and the ownership of each Subsidiary's respective capital
interests,  are  as  shown  in  Section  3.4  of the  Disclosure  Schedule.  The
percentage ownership interests in each of the non-corporate  Subsidiaries are as
shown  in  Section  3.4  of the  Disclosure  Schedule.  All  of the  outstanding
ownership  interests  of the  Subsidiaries  have been duly  authorized,  validly
issued and are fully paid and nonassessable. There are no preemptive rights with
respect to any such ownership  interests.  Except as shown in Section 3.4 of the
Disclosure Schedule, each of MAA and MAI owns their respective interests in each
Subsidiary  beneficially and of record free and clear of all Liens. There are no
outstanding   agreements,    subscriptions,   options,   warrants,   convertible
securities,  calls,  commitments or rights of any kind (contingent or otherwise)
pertaining  to the issuance or purchase of any  securities of MAA, MAI or any of
the Subsidiaries.

             Section  3.5  Corporate  Records.  Purchaser  and  AMSC  have  been
                           ------------------
provided with current,  correct and complete copies of all charter  documents or
partnership  agreements,  as the case may be, of MAA, MAI and the  Subsidiaries,
respectively,  including all amendments  thereto and restatements  thereof.  The
stock record books,  or comparable  ownership  record books,  of MAA, MAI and of
each of the Subsidiaries,  respectively,  are also current, correct and complete
and reflects the issuance of all of the Shares to Seller.  All existing  minutes
of meetings and resolutions of MAA, MAI and the Subsidiaries  have been provided
to Purchaser  and AMSC and are correct,  and there have been no other actions or
proceedings  of  MAA's,  MAI's  or any  Subsidiary's  shareholders,  members  or
partners,  as the case may be, or boards of  directors,  managers or  committees
thereof of a nature which would have to be disclosed  under this  Agreement that
has not been so disclosed.


             Section 3.6  Employee Benefit Plans.
                          ----------------------

                      (a)  Section 3.6(a) of  the Disclosure Schedule contains a
true  and  complete  list  of the  Benefit  Plans.  Neither  MAA,  MAI,  nor any
Subsidiary has any formal plan or commitment, whether legally binding or not, to
create any  additional  plan or modify or change any existing  Benefit Plan that
would affect any employee or director or former  employee or former  director of
MAA, MAI or any Subsidiary.

                         (b) With respect to each of the Benefit  Plans,  Seller
has  heretofore  delivered  to AMSC  true  and  complete  copies  of each of the
following  documents:  (i) the Benefit Plan and related documents (including all
amendments  thereto);  (ii)  the  two  most  recent  annual  reports,  financial
statements,  and actuarial  reports,  if any; (iii) the most recent summary plan
description,  together  with each  summary of material  modifications,  required
under  ERISA with  respect  to such  Benefit  Plan,  and all  material  employee
communications  relating  to  such  Benefit  Plan;  and  (iv)  the  most  recent
determination  letter  received  from the IRS with  respect to each Benefit Plan
that is intended to be qualified under the Code and all material  communications
to or from the IRS or any other governmental or regulatory authority relating to
each Benefit Plan.

                         (c) No  liability  under  Title  IV of  ERISA  has been
incurred by ARDIS or any ERISA  Affiliate  that has not been  satisfied in full,
and no  condition  exists  that  presents  a  material  risk to MAA,  MAI or any
Subsidiary of incurring a liability under such Title.  None of the Benefit Plans
is subject to Title IV of ERISA.

                         (d) Neither MAA, MAI nor any Subsidiary, nor any of the
Benefit  Plans,   nor  any  trust  created   thereunder,   nor  any  trustee  or
administrator  thereof  has  engaged in a  prohibited  transaction  (within  the
meaning of Section 406 of ERISA and Section 4975 of the Code) in connection with
which MAA, MAI, or any Subsidiary  could incur,  either  directly or indirectly,
liability for either a civil penalty assessed  pursuant to Section 409 or 502(i)
of ERISA or a tax imposed  pursuant  to Section  4975 or 4976 of the Code or any
other liability or cost.

                         (e)  Full  payment  has been  made,  or will be made in
accordance with Section  404(a)(6) of the Code, of all amounts that ARDIS or any
ERISA  Affiliate  is required to pay under  Section 412 of the Code or under the
terms of the Benefit Plans,  and all amounts that have not been paid by MAA, MAI
or any  Subsidiary  under the Benefit  Plans are  properly  accrued  through the
Closing Date and recorded on the Closing Financial Statements.

                         (f) None of the Benefit Plans is a Multiemployer  Plan,
a "multiple  employer  welfare  arrangement," as such term is defined in Section
3(40) of ERISA,  or a single  employer  plan  that has two or more  contributing
sponsors, at least two of whom are not under common control,  within the meaning
of Section 4063(a) of ERISA.

                         (g) Each of the  Benefit  Plans that is  intended to be
"qualified"  within the meaning of Section  401(a) of the Code is so  qualified,
and a  determination  letter  to that  effect  has been  issued  by the IRS with
respect to each such Benefit Plan. Each of the Benefit Plans that is intended to
satisfy the  requirements of Section 125 or 501(c)(9) of the Code satisfies such
requirements.  Each of the Benefit Plans has been operated and  administered  in
all  material  respects  in  accordance  with its  terms  and  applicable  laws,
including but not limited to ERISA and the Code.

                         (h) There are no actions,  suits or claims pending, or,
to the  knowledge  of Sellers,  threatened  or  anticipated  (other than routine
claims for benefits) against any Benefit Plan, the assets of any Benefit Plan or
against ARDIS or any ERISA Affiliate with respect to any Benefit Plan.  There is
no judgment, decree, injunction,  rule or order of any court, governmental body,
commission,  agency or arbitrator outstanding against or in favor of any Benefit
Plan or any fiduciary thereof (other than rules of general applicability). There
are no pending or threatened audits or investigations by any governmental  body,
commission or agency involving any Benefit Plan.

                         (i)  No  Benefit  Plan  provides  benefits,   including
without  limitation  death or medical  benefits  (whether or not insured),  with
respect to current or former  employees or directors  after  retirement or other
termination of service (other than (i) coverage mandated by applicable law, (ii)
death benefit or retirement  benefits under any "employee pension plan," as that
term is defined in Section 3(2) of ERISA, (iii) deferred  compensation  benefits
accrued as  liabilities  on the ARDIS Balance Sheet or (iv)  benefits,  the full
cost of which is borne by the current or former  employee  or  director  (or his
beneficiary)).

                         (j)  None  of the  assets  of  the  Benefit  Plans  (i)
constitute  employer real property or employer securities (within the meaning of
Section  407(d) of ERISA),  or (ii) are  invested in any  property,  security or
other ownership interest that is not publicly traded.

                         (k) The consummation of the  transactions  contemplated
by this  Agreement  will not (i)  entitle  any  current  or former  employee  or
director  of  MAA,  MAI,  or  any  Subsidiary  to  severance  pay,  unemployment
compensation or any similar  payment,  or (ii) accelerate the time of payment or
vesting,  or increase the amount, of any compensation due to any such current or
former employee or director,  or (iii) renew or extend the term of any agreement
regarding  compensation for any such current or former employee or director.  On
and  after  January  1,  1997,  except  as set  forth on  Section  3.6(k) of the
Disclosure  Schedule no employee  or former  employee of MAA,  MAI or any of the
Subsidiaries has become covered by, or a participant in, the ARDIS  Supplemental
Executive Retirement Plan, Long-Term Incentive Plan, or Retention Bonus Plan.

               Section  3.7  Broker's  or  Finder's  Fees.  No  agent,   broker,
                             ----------------------------
investment  banker,  person  or firm  acting  on  behalf  of Seller or under its
authority is or will be  entitled,  directly or  indirectly,  to collect from or
otherwise hold Purchaser,  AMSC, MAA, MAI or any of the Subsidiaries  liable for
any  broker's  or  finder's  fee or  any  other  commission  or  similar  fee in
connection with any of the transactions contemplated herein.


             Section 3.8 Financial Statements.  (a) The Financial Statements are
                         --------------------
complete copies of all of which have been delivered to Purchaser, present fairly
in all material  respects the financial  position and assets and  liabilities of
ARDIS Holding as of their  respective  dates,  and the results of its operations
for the fiscal periods then ended,  in conformity  with GAAP provided,  however,
that the Interim Financial Statements are subject to normal, year-end adjustment
and lack  footnotes  and other  presentation  items.  On the Closing  Date,  the
consolidated balance sheet of ARDIS Holding as of December 31, 1997, the related
consolidated  statements  of income and retained  earnings and notes thereto for
the  12-month  period then ended,  examined  by KPMG Peat  Marwick,  independent
certified public accountants, a complete copy of which shall have been delivered
to Purchaser  prior to the Closing Date,  shall  present  fairly in all material
respects the financial  position and assets and  liabilities of ARDIS Holding as
of December 31, 1997,  and the results of its  operations  for the fiscal period
then ended,  in conformity  with GAAP.  All  references in this Agreement to the
"ARDIS  Balance  Sheet Date"  shall be deemed to refer to  September  30,  1997;
provided,  however, that on the Closing Date all references in this Agreement to
the "ARDIS Balance Sheet Date" shall be deemed to refer to the audited  December
31, 1997.

                    (b) Neither Seller nor any other Person regularly  compiles,
maintains or prepares  financial  statements  for MAI or MAA.  Each of MAA, MAI,
ARDIS Holding and Radio Data Network Holding  Corporation  undertakes no regular
financial  or  business  activities  and has no material  assets  other than its
ownership interests in the Subsidiaries.

          Section 3.9 Accounts  Receivable.  All accounts receivable included in
                      --------------------
the calculation of the actual Closing  Working  Capital  pursuant to Section 2.4
will have arisen only in the ordinary  course of business,  consistent with past
practice, and will not be subject to defenses, set-offs or counterclaims. All of
such accounts receivable are generally due within 30 days after being accrued on
the books of ARDIS. The allowance for such doubtful  accounts in the calculation
of the  actual  Closing  Working  Capital  pursuant  to  Section  2.4  has  been
determined in accordance with GAAP.

          Section 3.10 Absence of Undisclosed  Liabilities.  Except as disclosed
                       -----------------------------------
in Section 3.10 of the Disclosure Schedule or elsewhere in this Agreement or the
Disclosure  Schedule,  neither MAA nor MAI has any  liabilities or  obligations,
either  accrued,  absolute,  contingent  or  otherwise.  Except as  disclosed in
Section 3.10 of the  Disclosure  Schedule or elsewhere in this  Agreement or the
Disclosure   Schedule,   none  of  the   Subsidiaries  has  any  liabilities  or
obligations, either accrued, absolute, contingent or otherwise, except:

                    (a) those  liabilities or obligations set forth on the ARDIS
Balance Sheet and not heretofore paid or discharged;

                    (b)  liabilities  arising in the ordinary course of business
under any agreement,  contract, commitment, lease or plan specifically disclosed
on the Disclosure  Schedule or not required to be disclosed  because of the term
or amount involved or otherwise; and

                    (c) those liabilities or obligations incurred,  consistently
with past business practice, in or as a result of the normal and ordinary course
of business since the ARDIS Balance Sheet Date.

             For purposes of this Section, the term "liabilities" shall include,
without limitation, any direct or indirect indebtedness,  guaranty, endorsement,
claim, loss, damage,  deficiency,  cost, expense,  obligation or responsibility,
known  or  unknown,  fixed  or  unfixed,  choate  or  inchoate,   liquidated  or
unliquidated, secured or unsecured.

             Section 3.11   Existing  Condition.  Except as disclosed in Section
                            -------------------
3.11 of the Disclosure Schedule,  since December 31, 1996 in the case of MAA and
MAI and since  the ARDIS  Balance  Sheet  Date in the case of the  Subsidiaries,
neither MAA, MAI nor any of the Subsidiaries has:

                    (a)  declared,  set  aside or paid any  dividend  or made or
agreed to make any other  distribution  or payment  in  respect  of its  capital
shares or  redeemed,  purchased  or  otherwise  acquired  or  agreed to  redeem,
purchase or acquire any of its capital shares;

                    (b)  incurred  any   liabilities,   other  than  liabilities
incurred in the ordinary course of business  consistent  with past practice,  or
discharged or satisfied any lien or encumbrance, or paid any liabilities,  other
than in the ordinary course of business consistent with past practice, or failed
to pay or  discharge  when due any  liabilities  of which the  failure to pay or
discharge  has caused or is  reasonably  expected  to cause a  Material  Adverse
Effect;

                    (c)  sold,  assigned  or  transferred  any of its  assets or
properties  except in the  ordinary  course  of  business  consistent  with past
practice;

                    (d)   created,   incurred,   assumed   or   guaranteed   any
indebtedness for money borrowed, or mortgaged, pledged or subjected to any Lien,
conditional  sales contract or other encumbrance of any nature whatsoever any of
its assets or properties, other than Permitted Liens;

                    (e)  made  or  suffered  any   material   amendment  or  any
termination of any material agreement,  contract,  commitment,  lease or plan to
which it is a party or by which it is bound,  or  cancelled,  modified or waived
any debts or claims held by it,  other than in the  ordinary  course of business
consistent with past practice;

                    (f) suffered any damage, destruction or loss, whether or not
covered by  insurance  which has had a Material  Adverse  Effect or suffered any
repeated, recurring or prolonged shortage, cessation or interruption of supplies
or utility services required to conduct its business and operations;

                    (g) suffered any Material  Adverse  Change after taking into
account all disclosures set forth on the Disclosure Schedule;

                    (h)  received  notice  or has  knowledge  of any  actual  or
threatened labor, union organizing effort, strike or other occurrence,  event or
condition or any similar character which has had or could reasonably be expected
to have a Material Adverse Effect;

                    (i)  received  any notice or has any  knowledge of any basis
for  assertions  of  liability,   claims,  causes  of  action,  charges,  suits,
complaints,    administrative   proceedings,    government   investigations   or
proceedings,  arbitrations or other  proceedings  pending or threatened  against
MAA, MAI or any of the  Subsidiaries  relating to any current or former employee
or director of MAA, MAI or any of the  Subsidiaries,  or any  federal,  state or
local laws and  regulations  thereunder or the common law relating to employment
or employment practices of MAA, MAI or any of the Subsidiaries;

                    (j) made any  capital  expenditure  or capital  addition  or
betterment  except such as may be involved in ordinary  repair,  maintenance and
replacement of its assets;

                    (k) increased the salaries or other compensation of, or made
any advance (excluding advances for ordinary and necessary business expenses) or
loan to, any of its shareholders, partners, directors, officers or employees, or
made any increase  in, or any  addition  to, other  benefits to which any of its
shareholders,  partners,  directors, officers or employees may be entitled other
than in the ordinary cause of business;

                    (l) changed any of the accounting  principles followed by it
or the methods of applying such principles; or

                    (m) entered into any transaction  other than as contemplated
by this  Agreement or in the ordinary  course of business  consistent  with past
practice.

             Section 3.12 Title to Properties; Leasehold Interests. MAA, MAI and
                          ----------------------------------------
each of the  Subsidiaries  has valid title to all of its  properties and assets,
real,  personal  and  mixed,  including  all  Real  Property,  and  all of  such
properties and assets free and clear of all Liens,  except  Permitted  Liens and
those items  disclosed in Section 3.12 of the Disclosure  Schedule.  All leases,
licenses,  permits  and  authorizations  in any  manner  related  to the real or
personal  properties used by MAA, MAI or any of the  Subsidiaries  and all other
instruments,  documents and agreements  pursuant to which MAA, MAI or any of the
Subsidiaries has obtained the right to use any real or personal  property are in
good standing,  valid and effective in accordance with their  respective  terms,
and there is not under any of such  instruments,  documents  or  agreements  any
existing  default or event  which with notice or lapse of time,  or both,  would
constitute a default and in respect of which MAA, MAI or any of the Subsidiaries
has not taken adequate steps to prevent a default from occurring.

               Section  3.13  Condition  of  Tangible  Assets.  All  buildings,
                              -------------------------------
structures,   facilities,   automobiles,   trucks,  other  vehicles,  machinery,
equipment  and other  material  items of  tangible  personal  property  owned or
operated by MAA,  MAI or any of the  Subsidiaries  are usable in the regular and
ordinary course of business of MAA, MAI or the  Subsidiaries  and conform in all
material  respects  to  all  applicable  laws,  ordinances,   codes,  rules  and
regulations relating to their construction,  use and operation.  The failure, if
any, of such  buildings,  structures,  facilities,  automobiles,  trucks,  other
vehicles,  machinery,  equipment and other material  items of tangible  personal
property  to  be in  good  operating  condition,  subject  to  normal  wear  and
maintenance, is not reasonably expected to have a Material Adverse Effect.

             Section  3.14  Books of  Account.  The  books  of  account of ARDIS
                            -----------------
reflect  all  of its  items  of  income  and  expense,  and  all of its  assets,
liabilities and accruals  required to be reflected  therein,  in accordance with
GAAP.

             Section  3.15  Litigation.  Except as listed in Section 3.15 of the
                            ---------- 
Disclosure  Schedule,  no  litigation,   arbitration,   investigation  or  other
proceeding  of or before any court,  arbitrator  or  governmental  or regulatory
official,  body  or  authority  is  pending  or,  to the  knowledge  of  Seller,
threatened  against  MAA,  MAI  or  any of the  Subsidiaries  or  their  assets,
properties or business,  or the  transactions  contemplated  by this  Agreement.
Other than as listed in Section 3.15 of the  Disclosure  Schedule,  neither MAA,
MAI nor any of the  Subsidiaries  is a party to or subject to the  provisions of
any judgment, order, writ, injunction,  decree or award of any court, arbitrator
or governmental or regulatory official, body or authority.

             Section  3.16  Compliance  with  Law.  MAA,  MAI  and  each  of the
                            ---------------------
Subsidiaries  has  complied  with each,  and is not in  violation  of any,  law,
ordinance,  or governmental  rule or regulation to which they or their business,
operations,  assets or properties are subject and has not failed to obtain or to
adhere to the requirements of any license,  permit or authorization necessary to
the  ownership of its assets and  properties  or to the conduct of its business,
which  noncompliance,  violation  or  failure  to  obtain  or  adhere  to  would
reasonably be expected to have a Material Adverse Effect.  Neither MAA, MAI, any
of the  Subsidiaries nor any officer,  employee or agent thereof,  or consultant
thereto has unlawfully offered,  paid, or agreed to pay, directly or indirectly,
any money or anything of value to, or for the benefit of, any  individual who is
or was a  candidate  for  public  office,  or an  official  or  employee  of any
governmental  or  regulatory  body or authority or an officer or employee of any
client, customer or supplier of MAA, MAI or any of the Subsidiaries.

             Section 3.17 Environmental Matters.  Section 3.17 of the Disclosure
                          ---------------------
Schedule  contains an accurate and  complete  description  of all  Environmental
Liabilities,  investigations, actions, proceedings of whatsoever nature, whether
pending or to Seller's  knowledge  threatened,  involving MAA, MAI or any of the
Subsidiaries or their respective  properties,  assets,  operations or businesses
arising under any Environmental  Law. Except as specified in Section 3.17 of the
Disclosure  Schedule:  (a) the  business of MAA, MAI and the  Subsidiaries,  the
methods and means  employed by MAA, MAI and the  Subsidiaries  in the  operation
thereof (including all operations and conditions at or in the properties of MAA,
MAI and the  Subsidiaries),  and the assets owned,  leased,  held or operated by
MAA,  MAI and  the  Subsidiaries,  comply  in all  material  respects  with  all
Environmental  Laws; (b) MAA, MAI and the Subsidiaries have obtained all permits
under Environmental Laws necessary to their operations, and all such permits are
in good standing and MAA, MAI and the  Subsidiaries  are in compliance  with all
material terms and conditions of such permits;  and (c) neither MAA, MAI nor any
of the  Subsidiaries  has received (i) any written claim or notice of violation,
lien, complaint, suit, order or other written claim or notice to the effect that
it is or may be  liable  to any  Person  as a  result  of (A) the  environmental
condition of any of their  respective  properties or any other property,  or (B)
the release or threatened release of any Hazardous Materials, or (ii) any letter
or request for information under Section 104 of CERCLA or comparable state laws,
and  to  Seller's  knowledge,  none  of  the  operations  of  MAA,  MAI  or  the
Subsidiaries  are the subject of any federal or state  investigation  evaluating
whether  any  remedial  action is needed to respond  to a release or  threatened
release,  of any  Hazardous  Material  at  MAA's,  MAI's  or  the  Subsidiaries'
properties or at any other location, including any location to which MAA, MAI or
the Subsidiaries have transported,  or arranged for the  transportation  of, any
Hazardous Materials.

             Section 3.18  Insurance.  Section 3.18 of the  Disclosure  Schedule
                           ---------
contains a correct and  complete  list of all  insurance  policies or binders of
insurance  held by or on behalf  ARDIS  relating  to its  business or any of its
assets or properties  (specifying the insurer,  the amount of the coverage,  the
type of insurance,  the risks insured and any pending  claims  thereunder).  The
policies and binders  listed in Section 3.18 of the Disclosure  Schedule  hereto
are duly in force as of the date hereof. There is no default with respect to any
material  provision  contained in any such policy or binder,  nor has there been
any  failure to give any notice or present  any claim  under any such  policy or
binder in a timely fashion or in the manner or detail  required by the policy or
binder.  There  are no  outstanding  unpaid  premiums  or  claims.  No notice of
cancellation  or nonrenewal with respect to, or disallowance of any claim under,
any  such  policy  or  binder  has  been  received  by  MAA,  MAI  or any of the
Subsidiaries.  Section 3.18 of the Disclosure  Schedule also contains a true and
complete  description  of all  outstanding  bonds and other surety  arrangements
issued or entered into in  connection  with the business and  operations of MAA,
MAI or any of the Subsidiaries.

             Section  3.19   Contracts  and  Commitments.   Except as listed and
                             ---------------------------
described in Section 3.19 of the Disclosure  Schedule,  neither MAA, MAI nor any
of the Subsidiaries is a party to any written or oral:

                    (a)  agreement,  contract or commitment  with any present or
former  shareholder,  director,  officer,  employee  or  consultant  or for  the
employment of any person,  including any  consultant  pursuant to which payments
thereunder are  obligations of MAA, MAI or any Subsidiary  which are not payable
by Seller;

                    (b) agreement,  contract, commitment or arrangement with any
labor union or other representative of employees;

                    (c) agreement,  contract, commitment for the future purchase
of, or payment for, supplies or products,  or for the performance of services by
a third party, involving in any one case $50,000 or more;

                    (d)  agreement,  contract,  commitment  to  sell  or  supply
products or to perform services, having with respect to revenues to be delivered
or potential  liabilities  reasonably to be incurred in any one case $100,000 or
more on an annual basis;

                    (e) agreement,  contract, commitment not otherwise listed on
the Disclosure  Schedule and continuing over a period of more than twelve months
from the date hereof or exceeding $100,000 in value;

                    (f) lease for office  space under  which MAA,  MAI or any of
the Subsidiaries is either the lessor or lessee;

                    (g) agreement,  contract or commitment for any charitable or
political contribution;

                    (h)  agreement,  contract,  or  commitment  for any  capital
expenditure in excess of $100,000;

                    (i)   agreement,   contract   or   commitment   limiting  or
restraining  it from  engaging or  competing  in any lines of business  with any
person,  and  neither  Seller nor any officer or employee of ARDIS is subject to
any such  agreement,  contract  or  commitment  which would  prohibit  them from
continuing their employment in the same capacity as that in which they currently
perform services for ARDIS; or

                    (j) agreement, contract or commitment by or between MAA, MAI
or any of the  Subsidiaries  and Seller or any  Affiliate of Seller  (other than
MAA, MAI or any of the Subsidiaries).

             Except  as may be  disclosed  in  Section  3.19  of the  Disclosure
Schedule, to Seller's knowledge, each of the agreements, contracts, commitments,
leases  and  other  instruments,   documents  and  undertakings  listed  on  the
Disclosure  Schedule  is in full  force  and  effect;  Seller,  MAI,  MAA or the
Subsidiaries  which are parties  thereto,  and, to the knowledge of Seller,  all
other parties thereto are in compliance with the provisions  thereof and are not
in  default  in the  performance,  observance  or  fulfillment  of any  material
obligation,  covenant or condition  contained  therein and no event has occurred
which with or  without  the  giving of notice or lapse of time,  or both,  would
constitute  a default  thereunder  by MAI,  MAA or the  Subsidiaries  or, to the
knowledge  of  Seller,  by any  other  parties  thereto;  and,  except as may be
disclosed  on the  Disclosure  Schedule,  to the  knowledge  of Seller,  no such
agreement,  contract,  commitment,  lease  or  other  instrument,   document  or
undertaking,  in the  reasonable  opinion of Seller,  contains  any  contractual
requirement  with  which  there  is  a  reasonable   likelihood  MAA,  MAI,  the
Subsidiaries or any other party thereto will be unable to comply,  assuming that
MAA, MAI and the  Subsidiaries  continue in all  material  respects to be in the
same financial condition as they are as of the date hereof.

             Section  3.20   Additional   Information.    Section  3.20  of  the
                             ------------------------
Disclosure  Schedule,  to the extent not described  elsewhere in the  Disclosure
Schedule, contains accurate lists and summary descriptions of the following:

                    (a)  all  real  property  and  interests  in  real  property
(including Realty Rights) owned,  leased or otherwise held by MAA, MAI or any of
the Subsidiaries other than antennae and transmitter sites (collectively,  "Real
Property")  as of the date  hereof  which  listing  shall be  updated  as of the
Closing,  specifying  which are owned,  which are  leased  and which  constitute
Realty  Rights  and,  (i) with  respect  to the  owned  Real  Property,  if any,
specifying  its cost or  original  value and the net book  value as of the ARDIS
Balance  Sheet  Date and (ii) with  respect  to leased  or  otherwise  held Real
Property, the current term of ownership and rental rate applicable thereto;

                    (b) all machinery,  vehicles and equipment owned by MAA, MAI
or the Subsidiaries  which has an original cost of at least $50,000,  specifying
the cost thereof and the net book value  thereof as of the ARDIS  Balance  Sheet
Date;

                    (c) the names of all present  officers and directors of MAA,
MAI and each of the Subsidiaries;

                    (d)  the  names  and  addresses  of  every  bank  and  other
financial institution in which MAA, MAI or any of the Subsidiaries  maintains an
account (whether checking, savings or otherwise),  lock box or safe deposit box,
and the account  numbers and names of persons having signing  authority or other
access thereto;

                    (e) the names of all persons  authorized  to borrow money or
incur  indebtedness  for  borrowed  money on  behalf  of MAA,  MAI or any of the
Subsidiaries or obligate MAA, MAI or any of the Subsidiaries as a guarantor with
respect to indebtedness for borrowed money; and

                    (f) the names of all persons holding powers of attorney from
MAA,  MAI or any  of the  Subsidiaries  and a  summary  statement  of the  terms
thereof.

             Section 3.21  Intellectual Property.
                           ---------------------

                    (a) Section  3.21(a) of the Disclosure  Schedule  accurately
lists  all  of  the  Intellectual  Property  owned  by  MAA,  MAI  or any of the
Subsidiaries  which has been duly registered with, filed in or issued by, as the
case may be, the United  States  Patent and  Trademark  Office,  U.S.  Copyright
Office, or any similar  governmental agency in any foreign country, as indicated
in Section 3.21(a) of the Disclosure  Schedule.  Unless  otherwise  indicated in
such Section 3.21(a),  MAA, MAI or the Subsidiaries own the entire right,  title
and  interest  in  and  to  such  Intellectual   Property  (including,   without
limitation,  the  exclusive  right to use and license  the same).  Except as set
forth in Section 3.21(a) of the Disclosure Schedule, neither MAA, MAI nor any of
the  Subsidiaries  has granted,  any license or other right with respect to such
Intellectual  Property  which does or which  will,  subsequent  to the  Closing,
permit or enable any Person other than MAA, MAI or the  Subsidiaries to use such
Intellectual Property. To the knowledge of Seller, no such Intellectual Property
or MAA's,  MAI's or the  Subsidiaries'  use  thereof,  infringes or violates the
rights of third  parties.  To the  knowledge of Seller,  MAA and MAI,  except as
indicated in Section 3.21(a) of the Disclosure Schedule, no Person is infringing
upon  any  of  the  Intellectual  Property  listed  in  Section  3.21(a)  of the
Disclosure Schedule.

                    (b) Set forth in Section 3.21(b) of the Disclosure  Schedule
is a list of all Intellectual  Property owned by third parties which is licensed
to, or otherwise  used in the business of, MAA, MAI or any of the  Subsidiaries.
All such Intellectual Property is licensed pursuant to valid written agreements.
MAA's, MAI's or the Subsidiaries use of such listed Intellectual  Property owned
by Seller or any of its  Affiliates  (other than MAA, MAI or the  Subsidiaries),
does not  infringe  or violate the rights of third  parties.  Except only as set
forth in Section  3.21(b)  of the  Disclosure  Schedule,  there is no pending or
threatened  written  claim  against MAA, MAI or any of the  Subsidiaries,  or to
Seller's  knowledge,  the  licensors  of  such  licensed  Intellectual  Property
asserting that any of such licensed  Intellectual  Property,  or MAA's, MAI's or
the Subsidiaries' use thereof, infringes or violates the rights of third parties
or that MAA, MAI or any of the Subsidiaries is in breach of any such agreement.

                    (c)  To  the   knowledge   of  Seller,   MAA,  MAI  and  the
Subsidiaries  own or have the  right to use all  Intellectual  Property  used in
their  businesses  as  conducted on the date hereof.  Upon  consummation  of the
transactions  contemplated by this Agreement, MAA, MAI and the Subsidiaries will
be entitled to continue to use all Intellectual Property used in the business of
MAA, MAI or the  Subsidiaries  as it is used to conduct their business as of the
Closing  Date  without any  limitation,  impairment  or  alteration  thereof and
without the payment of any fees or license or other payments. Section 3.21(c) of
the Disclosure Schedule lists all written notices or claims received by MAA, MAI
or  any  of  the  Subsidiaries  which  claim  infringement  by  MAA,  MAI or the
Subsidiaries  of any  Intellectual  Property which is claimed to be owned by any
other person.  To the knowledge of Seller,  there is no basis for any such claim
listed in Section 3.21(c) of the Disclosure Schedule.

              Section  3.22 No  Third  Party  Options.  There  are  no  existing
                            -------------------------
agreements,  options, commitments or rights with, to or in any person to acquire
any of MAA, MAI or any of the Subsidiaries' assets or properties or any interest
therein,  except for this  Agreement  and those  contracts  entered  into in the
normal  course of business  consistent  with past practice for the sale of MAA's
MAI's or any Subsidiary's products or services.


             Section 3.23  Tariffs; FCC Licenses; Non-FCC Authorizations.
                           ---------------------------------------------

                    (a) Section  3.23(a) of the  Disclosure  Schedule lists each
tariff  applicable to MAA, MAI or any of the Subsidiaries as of the date hereof,
a true  and  correct  copy of each of  which  has  been or will be  provided  to
Purchaser.  Except as otherwise set forth in Section  3.23(a) of the  Disclosure
Schedule,  (i) such  tariffs  stand in full  force and  effect,  and there is no
outstanding notice of cancellation or termination or, to Seller's knowledge, any
threatened  cancellation  or termination in connection  therewith,  (ii) neither
MAA,  MAI nor  any of the  Subsidiaries  is  subject  to,  any  restrictions  or
conditions applicable to such tariffs that limit or would limit the operation of
its business  (other than  restrictions  or conditions  generally  applicable to
tariffs  of that  type).  Neither  MAA,  MAI nor any of the  Subsidiaries  is in
violation  under the terms and  conditions  of any of its  tariffs in any manner
which could  reasonably be expected to result in a Threshold Amount with respect
to MAA, MAI or any of the  Subsidiaries.  Except as set forth in Section 3.23(a)
of the Disclosure Schedule,  there are no applications by MAA, MAI or any of the
Subsidiaries or to Seller's knowledge,  complaints, filings, orders or petitions
by others or proceedings pending or threatened before the appropriate regulatory
authority  relating to the business or operations or regulatory  tariffs of MAA,
MAI or any of the Subsidiaries as of the date hereof.

                    (b) Section  3.23(b) of the  Disclosure  Schedule lists each
FCC License  held by MAA, MAI or any of the  Subsidiaries  as of the date hereof
which list shall be updated as of the  Closing  Date.  Except as  otherwise  set
forth  in  Section  3.23(b)  of  the  Disclosure  Schedule,  such  FCC  Licenses
constitute  all FCC Licenses  necessary  for the conduct of the business of MAA,
MAI and each of the  Subsidiaries as conducted and as anticipated as of the date
hereof to be  conducted  in the 12 month  period  following  the date hereof and
thereafter as contemplated in material  respects under the UPS Contract.  Except
as otherwise set forth in Section 3.23(b) of the Disclosure Schedule,  each such
FCC License is in full force and effect,  and there is no outstanding  notice of
cancellation   or  termination  or,  to  Seller's   knowledge,   any  threatened
cancellation or termination in connection  therewith.  None of such FCC Licenses
is  subject to any  restrictions  or  conditions  except as set forth on Section
3.23(b) of the Disclosure  Schedule that limit the operations of MAA, MAI or any
of the Subsidiaries (other than restrictions or conditions  generally applicable
to  licenses  of that  type).  Subject  to the  Communications  Act of 1934,  as
amended,  and the  regulations  thereunder,  the FCC  Licenses are free from all
security  interests,  liens,  claims, or encumbrances of any nature  whatsoever.
Except as set forth in Section 3.23(b) of the Disclosure Schedule,  there are no
applications by MAA, MAI or any of its Subsidiaries  or, to Seller's  knowledge,
complaints or petitions by others or  proceedings  pending or threatened  before
the FCC  relating  to the  business or FCC  Licenses  of MAA,  MAI or any of the
Subsidiaries  as of the date  hereof or which  could  reasonably  be expected to
result in a Threshold Amount with respect to MAA, MAI or any of the Subsidiaries
as of the Closing Date.

                    (c) Section  3.23(c) of the  Disclosure  Schedule  lists all
material  Non-FCC  Authorizations  necessary  for the conduct of the business of
MAA, MAI and each of the  Subsidiaries as of the date hereof which list shall be
updated as of the Closing Date. Except as otherwise set forth in Section 3.23(c)
of the Disclosure Schedule,  each such material Non-FCC Authorization is in full
force and  effect.  No event has  occurred  with  respect  to any such  material
Non-FCC  Authorization  which (i)  permits,  or after notice or lapse of time or
both would permit,  revocation or termination  thereof,  or (ii) would result in
any other impairment of the rights of the holder of such Non-FCC Authorization.

             Section 3.24  Officer and Employee Compensation.  Section 3.24 of 
                           ---------------------------------
the Disclosure  Schedule lists each officer and employee of MAA, MAI and each of
the  Subsidiaries  and  such  officer's  or  employee's   corresponding   annual
compensation  amount  payable by any of MAA,  MAI or any such  Subsidiary  as of
December 31, 1997.


             Section  3.25  Indebtedness.  Neither  MAA,  MAI  nor  any  of  the
                            ------------
Subsidiaries  is  subject  to any note,  debenture,  bond,  conditional  sale or
equipment trust agreement,  letter of credit agreement, loan agreement, or other
contract or commitment for the borrowing or lending of money (including, without
limitation, loans to or from officers,  directors,  shareholders, or any members
of their immediate families),  any non-vendor financing  arrangement with Seller
or any  Affiliate of Seller (other than the  Subsidiaries),  or any agreement or
arrangement  for a line of credit,  or guarantee,  pledge or  undertaking of the
indebtedness of any other Person.

             Section 3.26  Access; Sophistication; etc.
                           ----------------------------

                    (a)  Purchaser  and AMSC have  furnished to Seller copies of
their  respective  most recent  financial  statements  and Seller in agreeing to
accept the AMSC Common Stock has reviewed such  documents and has relied only on
(i)  the   statements   and   information   contained   therein   and  (ii)  the
representations, warranties, terms and conditions of this Agreement.

                    (b)  Seller  acknowledges  that  all  documents,  books  and
records  requested by Seller  pertaining  to  Purchaser  and AMSC have been made
available  for  inspection  by Seller and its agents and  representatives;  that
Seller and its agents and representatives  have had a reasonable  opportunity to
ask  questions  of and receive  answers from  Purchaser  and AMSC or officers or
employees  acting on  behalf  of  Purchaser  and AMSC  concerning  the terms and
conditions  of the AMSC Common Stock and the business and prospects of Purchaser
and  AMSC.  Seller  and its  respective  agents  and  representatives  have such
knowledge and experience in financial and business  matters as to enable them to
utilize  the  information   made  available  to  them  in  connection  with  the
transactions  contemplated hereby, to evaluate the merits and risks of accepting
the AMSC Common Stock and to make an informed  decision with respect thereto and
such an evaluation and informed decision have been made.

             Section 3.27  Investment  Representation.  Seller is acquiring  the
                           --------------------------
shares of AMSC Common  Stock to be received by Seller upon  consummation  of the
sale of Seller's Shares to Purchaser for its own account for investment only and
not with a view to making a  distribution  thereof  within  the  meaning  of the
Securities  Act of 1933,  as  amended.  Seller  agrees  that it will not sell or
transfer such shares of AMSC Common Stock,  except in accordance  with the terms
of the legend set forth below, unless such shares are subsequently registered or
an exemption from registration is available.  Seller is aware that the shares of
AMSC Common Stock it is receiving have not been registered  under the Securities
Act of 1933, as amended, or any state or other  jurisdiction's  securities laws,
and that the  shares  of AMSC  Common  Stock  must be held  indefinitely  unless
subsequently  registered or an exemption  from such  registration  is available.
Seller is aware that it will not be readily able to liquidate its shares of AMSC
Common Stock. Seller understands and agrees that the shares of AMSC Common Stock
to be received by Seller will bear legends substantially to the effect set forth
below and that a stop transfer order may be placed with respect thereto.


             THE SHARES OF COMMON STOCK  REPRESENTED  BY THIS  CERTIFICATE  HAVE
BEEN ACQUIRED FOR INVESTMENT AND HAVE NOT BEEN  REGISTERED  UNDER THE SECURITIES
ACT OF 1933 OR THE  SECURITIES  LAWS OF ANY STATE,  AND MAY NOT BE  OFFERED  FOR
SALE, SOLD OR OTHERWISE  TRANSFERRED UNLESS  REGISTRATION  STATEMENTS UNDER SUCH
LAWS  ARE  THEN  IN  EFFECT  OR  UNLESS  AN  EXEMPTION  FROM  THE   REGISTRATION
REQUIREMENTS THEREOF IS THEN APPLICABLE TO SUCH OFFER OR SALE.

             The shares of Common Stock  represented  by  this  certificate  may
not be sold, transferred,  assigned, pledged, hypothecated or otherwise disposed
of except in  accordance  with the terms of the  Registration  Rights  Agreement
dated as of , 1998, a copy of which is on file at the office of the Corporation.



        ARTICLE 4. REPRESENTATIONS AND WARRANTIES OF AMSC AND PURCHASER

             AMSC and Purchaser each hereby represents and warrants to Seller as
follows:

             Section  4.1   Organization  and  Good  Standing.  Each of AMSC and
                            ---------------------------------
Purchaser is a corporation duly organized, validly existing and in good standing
under the laws of Delaware and has full corporate  power to conduct its business
as presently or then  conducted and to own and operate the assets and properties
now or then owned and operated by it.


             Section  4.2  Authority;   No  Required  Consents  or  Governmental
                           -----------------------------------------------------
Authorizations or Breach of Statute or Contract; Enforceability.
- ---------------------------------------------------------------

                    (a) Each of AMSC and Purchaser has the full corporate  power
and lawful authority to execute and deliver this Agreement and to consummate and
perform the transactions  contemplated hereby in the manner herein provided. The
execution  and  delivery  of  this  Agreement  by  AMSC  and  Purchaser  and the
consummation   and  performance  by  AMSC  and  Purchaser  of  the  transactions
contemplated  hereby in the manner  herein  provided  has been duly and  validly
authorized by all necessary corporate or other action.

                    (b) The AMSC Common Stock when issued to Seller will be duly
authorized,  validly  issued  free and  clear  of all  liens,  pledges,  claims,
security interests, options or other encumbrances of any nature whatsoever.

                    (c) Except for the applicable  requirements  of the HSR Act,
the AMSC Shareholder  Approval and, to the knowledge of AMSC and Purchaser,  the
Required  Consents,  neither the execution and delivery by AMSC and Purchaser of
this Agreement nor the consummation and performance by AMSC and Purchaser of the
transactions  contemplated hereby in the manner herein provided (i) requires the
approval,  consent or  authorization  of, or any  filing  with or notice to, any
federal,  state,  provincial,  local or other governmental agency or body or any
other third party, other than (A) approvals, consents,  authorizations,  filings
or notices of a character such that a failure to obtain, file or give them would
not  singly  or in the  aggregate  have a  material  adverse  effect on AMSC and
Purchaser  or  otherwise  impair or affect the  validity  of this  Agreement  or
prevent or hinder the consummation of the transactions  contemplated  hereby and
(B)  approvals,  consents,  authorizations,  filings or notices  which have been
obtained,  made or given,  or (ii)  conflicts with or will result in the uncured
and unwaived  breach or violation of any term or  provision  of,  constitutes  a
default under or will cause the acceleration of any payments pursuant to (A) the
Certificates of Incorporation or By-laws of AMSC and Purchaser, (B) any material
indenture,  mortgage,  deed of trust, lease, note or note agreement or any other
agreement or instrument to which either AMSC or Purchaser is a party or by which
either AMSC or Purchaser or any of their  respective  assets or  properties  are
bound,  (C) any  material  governmental  license,  franchise,  permit  or  other
authorization held by either AMSC or Purchaser or (D) any law, judgment,  order,
writ, injunction,  decree, award, rule or regulation of any court, arbitrator or
governmental agency or body applicable to either AMSC or Purchaser.

                    (d) This  Agreement,  when executed and delivered by Seller,
MAA and MAI and assuming the  enforceability  of this Agreement upon Seller will
be the  valid  and  binding  obligations  of AMSC  and  Purchaser,  and  will be
enforceable against AMSC and Purchaser in accordance with its terms,  subject to
bankruptcy,   insolvency  or  other  laws  affecting  the  rights  of  creditors
generally.

                    (e) Except as set forth on  Schedule  4.2,  there are no (i)
statutory,  contractual or other preemptive  rights with respect to the issuance
or transfer of any shares of AMSC Common Stock or other securities of AMSC; (ii)
outstanding  options,  warrants or rights to purchase,  repurchase  or otherwise
subscribe  for  any  equity  securities,  any  securities  convertible  into  or
exchangeable  for its capital stock or other ownership  interests of AMSC (other
than the  issuance  of AMSC Common  Stock  pursuant  to this  Agreement);  (iii)
obligations of AMSC, whether absolute or contingent,  to issue or repurchase any
shares of equity securities or other ownership interests or to share or make any
payments  based on its revenues,  profits or net income;  (iv)  indebtedness  or
securities  directly or  indirectly  convertible  into any equity  securities of
AMSC; or (v) voting trusts,  proxies,  or any other agreements,  restrictions or
understandings  with  respect to the voting of the capital  shares of AMSC or to
any other aspect of AMSC's affairs (including any registration rights).

               Section  4.3  Broker's  or  Finder's  Fees.  No  agent,   broker,
                             ----------------------------
investment banker,  person or firm acting on behalf of Purchaser,  AMSC or under
their authority is or will be entitled,  directly or indirectly, to collect from
or otherwise hold Seller, MAA, or MAI liable for any broker's or finder's fee or
any other  commission or similar fee in connection with any of the  transactions
contemplated herein.


             Section 4.4  Access; Sophistication; etc.
                          ----------------------------

                    (a) Seller, MAA and MAI have furnished to AMSC and Purchaser
copies  of  their  respective  most  recent  financial  statements  and AMSC and
Purchaser  in agreeing to accept the Shares  reviewed  such  documents  and have
relied only on (i) the statements and information contained therein and (ii) the
representations, warranties, terms and conditions of this Agreement.

                    (b)  Each  of  AMSC  and  Purchaser  acknowledges  that  all
documents,  books and records requested by AMSC or Purchaser  pertaining to MAA,
MAI and the  Subsidiaries  have been made  available for  inspection by AMSC and
Purchaser  and their agents and  representatives;  that AMSC and  Purchaser  and
their  agents  and  representatives  have had a  reasonable  opportunity  to ask
questions of and receive answers from Seller,  MAA, MAI and the  Subsidiaries or
officers or employees  acting on behalf of Seller,  MAA, MAI or the Subsidiaries
concerning the terms and conditions of the Shares and the business and prospects
of MAI, MAA and the Subsidiaries. AMSC and Purchaser and their respective agents
and representatives have such knowledge and experience in financial and business
matters as to enable them to utilize the  information  made available to them in
connection with the transactions contemplated hereby, to evaluate the merits and
risks of  accepting  the Shares and to make an informed  decision  with  respect
thereto and such an evaluation and informed decision have been made.

             Section 4.5 Investment  Representation.  Purchaser is acquiring the
                         --------------------------
Shares  to be  received  by  Purchaser  upon  consummation  of the  transactions
contemplated  herein for its own account for investment only and not with a view
to making a  distribution  thereof  within the meaning of the  Securities Act of
1933,  as  amended.  Purchaser  agrees  that it will not sell or  transfer  such
Shares,  except in  accordance  with the terms of the  legend  set forth  below.
Purchaser  is aware that the  Shares it is  receiving  have not been  registered
under  the  Securities  Act  of  1933,  as  amended,   or  any  state  or  other
jurisdiction's  securities  laws, and that the Shares must be held  indefinitely
unless  subsequently  registered  or an  exemption  from  such  registration  is
available.  Purchaser is aware that it will not be readily able to liquidate its
Shares.  Purchaser  understands  and agrees  that the Shares to be  received  by
Purchaser  will bear a legend  substantially  to the effect set forth  below and
that a stop transfer order may be placed with respect thereto.

             THESE SHARES HAVE NOT BEEN  REGISTERED  UNDER THE SECURITIES ACT OF
             1933,  AS  AMENDED,  OR  ANY  APPLICABLE   SECURITIES  LAW  OF  ANY
             JURISDICTION  AND MAY NOT BE  TRANSFERRED  UNTIL (A) A REGISTRATION
             STATEMENT UNDER SUCH SECURITIES ACT AND SUCH APPLICABLE  SECURITIES
             LAWS SHALL HAVE BECOME  EFFECTIVE WITH REGARD THERETO OR (B) IN THE
             OPINION  OF  COUNSEL   REASONABLY   ACCEPTABLE   TO  THE   COMPANY,
             REGISTRATION   UNDER  SUCH   SECURITIES  ACT  AND  SUCH  APPLICABLE
             SECURITIES  LAWS IS NOT REQUIRED IN  CONNECTION  WITH SUCH PROPOSED
             TRANSFER.

             Section 4.6  SEC Filings; Financial Statements.
                          ---------------------------------

                    (a)  AMSC has  made  available  to  Seller  a  complete  and
accurate copy of each report,  schedule,  registration  statement and definitive
proxy  statement  filed by AMSC  with the SEC on or after  January  1, 1996 (the
"AMSC SEC Reports"),  which are all the forms, reports and documents required to
be filed by AMSC with the SEC since such  date.  The AMSC SEC  Reports  complied
with the requirements of the Securities Act or the Exchange Act, as the case may
be at the times they were filed (or if amended or  superseded  by a filing prior
to the date of this Agreement then or the date of such filing).

                    (b) Each of the sets of  consolidated  financial  statements
(including,  in case, any notes  thereto)  contained in the AMSC SEC Reports was
prepared in accordance  with GAAP applied on a consistent  basis  throughout the
periods  involved and fairly presents in all material  respects the consolidated
financial  position of AMSC and its material  subsidiaries  as at the respective
dates thereof and the  consolidated  results of their  operations and cash flows
for  the  periods  indicated,   except  that  the  unaudited  interim  financial
statements were or are subject to normal year-end audit adjustments.

                    (c) AMSC has  previously  furnished to Seller a complete and
correct copy of any  amendments  or  modifications  that have not yet been filed
with the SEC but that are  required  to be filed in  agreements,  documents,  or
other  instruments which previously had been filed by AMSC with the SEC pursuant
to the Securities Act or the Exchange Act.

             Section 4.7  Absence of Certain Changes or Events.  Since September
                          ------------------------------------
30, 1997,  there has not been (a) any change,  or any development or combination
of  developments  of which  management of AMSC has  knowledge,  which has had or
would  reasonably be expected to have a material  adverse  effect on AMSC or (b)
any damages,  destruction or loss, whether or not covered by insurance which has
had or would reasonably be expected to have a material adverse effect on AMSC.

             Section  4.8   Absence  of   Undisclosed  Liabilities.   Except  as
                            --------------------------------------
disclosed in the AMSC SEC Reports or in this Agreement,  neither AMSC nor any of
its  Subsidiaries  has  liabilities or obligations,  either  accrued,  absolute,
contingent or otherwise,  except: 

                    (a) those liabilities or obligations set forth on the latest
balance sheet in the AMSC SEC Reports and not heretofore paid or discharged;

                      (b) liabilities arising in the ordinary course of business
under any agreement, contract, commitment, lease or plan; and

                    (c) those liabilities or obligations incurred,  consistently
with past business practice, in or as a result of the normal and ordinary course
of business since the date of the latest balance sheet set forth in the AMSC SEC
Reports.  For purposes of this Section,  the term  "liabilities"  shall include,
without limitation, any direct or indirect indebtedness,  guaranty, endorsement,
claim, loss, damage,  deficiency,  cost, expense,  obligation or responsibility,
known  or  unknown,  fixed  or  unfixed,  choate  or  inchoate,   liquidated  or
unliquidated, secured or unsecured.

             Section 4.9   Litigation.   Except  as  described  in  the AMSC SEC
                           ----------
Reports, no material litigation, arbitration, investigation, or other proceeding
of or before any court,  arbitrator or governmental or regulatory official, body
or authority is pending or, to the knowledge of AMSC, threatened against AMSC or
any of its Subsidiaries. Other than as so described, neither AMSC nor any of its
Subsidiaries is a party to or subject to the provisions of any judgment,  order,
writ, injunction or decre

                          ARTICLE 5. CERTAIN AGREEMENTS

             Section 5.1 Conduct of the Business. From the date hereof until the
                         ----------------------- 
Closing Date, except as otherwise contemplated by this Agreement or disclosed in
the Disclosure Schedule,  Seller shall, and shall cause MAA, MAI, ARDIS and each
of the  Other  Subsidiaries  to,  conduct  their  respective  businesses  in the
ordinary  course  consistent  with past practice and in such manner that, at the
Closing,  the representations and warranties of Seller shall be true and correct
in all  material  respects,  and  until  issuance  of a Final  Order,  AMSC  and
Purchaser  shall conduct the business of ARDIS in good faith.  Without  limiting
the  generality  of the  foregoing,  except as  otherwise  contemplated  by this
Agreement,  from the date  hereof  until the  Closing  Date,  without  the prior
written consent of AMSC and Purchaser, Seller will not permit MAA, MAI or any of
the Subsidiaries to:

                    (a) issue,  deliver,  sell,  dispose of, pledge or otherwise
encumber, or authorize or propose the issuance,  sale,  disposition or pledge or
other encumbrance of (x) any additional partnership interests or shares of their
capital  stock of any  class,  or any  securities  or rights  convertible  into,
exchangeable  for, or  evidencing  the right to  subscribe  for any  partnership
interests or shares of their capital stock,  or any rights,  warrants,  options,
calls,  commitments  or any other  agreements  of any  character  to purchase or
acquire  any  partnership  interests  or  shares of their  capital  stock or any
securities or rights convertible into, exchangeable for, or evidencing the right
to subscribe for, any partnership interests or shares of their capital stock, or
(y) any other  securities  in respect  of, in lieu of, or in  substitution  for,
partnership interests or shares outstanding on the date hereof;

                    (b) redeem,  purchase or  otherwise  acquire,  or propose to
redeem,  purchase or otherwise acquire, any of their outstanding  securities or,
in the case of MAA or MAI, to pay any dividends  (except for cash  dividends) or
make any other distributions to their respective shareholders;

                    (c) split,  combine,  subdivide or reclassify  any shares of
their capital stock;

                    (d) (i) grant any  increases in the  compensation  of any of
their  directors,  officers  or  employees,  except  in the  ordinary  course of
business,  (ii) pay or agree to pay any pension,  retirement  allowance or other
material  employee  benefit  not  required  by  any  of  the  existing  benefit,
severance,  pension or employment plans, agreements or arrangements as in effect
on the date hereof to any such director, officer or key employees,  whether past
or present, (iii) enter into any new or materially amend any existing employment
agreement with any such director,  officer or key employee,  (iv) enter into any
new or materially amend any existing severance agreement with any such director,
officer  or key  employee,  or (v)  except as may be  required  to  comply  with
applicable law, become obligated under any new Multiemployer Plan, Benefit Plan,
severance plan or arrangement,  which was not in existence on the date hereof or
amend by any such plan or  arrangement  in  existence  on the date hereof if the
effect thereof would be to enhance benefits thereunder;

                    (e)  adopt  a  plan  of  complete  or  partial  liquidation,
dissolution,  merger,  consolidation,  restructuring,  recapitalization or other
reorganization of MAA, MAI or any of the Subsidiaries;

                    (f) make any  acquisition by means of merger,  consolidation
or otherwise;

                    (g) adopt any  amendments  to their  Partnership  Agreement,
Certificate of Incorporation, charter or By-Laws;

                    (h) incur any  indebtedness  for borrowed money or guarantee
any such indebtedness or make any loans,  advances or capital  contributions to,
or investments  in, any other Person (other than to any of the  Subsidiaries  or
loans to their respective employees, in the ordinary course of business);

                    (i)  engage  in the  conduct  of  any  business  other  than
telecommunications and related businesses;

                    (j) enter into any agreement  providing for  acceleration of
payment or performance  or other  consequence as a result of a change of control
of MAA, MAI or any of the Subsidiaries;

                    (k) operate in other than the usual,  regular  and  ordinary
course and in accordance with past practices and, to the extent  consistent with
such operation and with the other covenants  contained  herein,  to use its good
faith  efforts to continue  normal  purchasing,  payments  of accounts  payable,
rental, leasing, renewal,  financing,  marketing,  advertising,  promotional and
maintenance  expenditures  with  respect  to the  business  of MAA,  MAI and the
Subsidiaries;  provided,  Seller  shall not on behalf of MAA,  MAI or any of the
Subsidiaries,  and shall not  permit  MAA,  MAI or any of the  Subsidiaries  to,
accelerate  or delay any payment of accounts  payable,  or bill any  customer in
advance beyond existing and usual contractual terms for services to be performed
after the date hereof;

                    (l) except as otherwise contemplated in this Agreement, fail
to maintain all authorizations and licenses materially necessary for the conduct
by MAA, MAI or the  Subsidiaries  of their  respective  businesses in accordance
with past custom and  practice,  including but not limited to failure to proceed
with any actions  necessary to ensure the  build-outs  referenced in the two FCC
orders,  each  dated  June 5,  1996,  granting  extensions  of time to  commence
services (No. 7110-02);

                    (m) fail to  maintain  all  insurance  policies  and binders
shown in Section  3.18 of the  Disclosure  Schedule  unless  new or  replacement
insurance policies or binders with similar coverage are obtained;

                    (n) submit or file with, except as otherwise contemplated in
this  Agreement,  or  otherwise  voluntarily  participate  as  a  party  to  any
stipulation, pleading, filing or other proceeding with the FCC, any state public
service  commission,  public utility  commission or similar state agency, or any
other regulatory  authority with  jurisdiction over MAA, MAI or the Subsidiaries
where such stipulation, pleading, filing or other proceeding could reasonably be
expected to result in a Threshold  Amount with respect to MAA, MAI or any of the
Subsidiaries or fail to notify AMSC promptly of any involuntary participation in
any of the foregoing;

                    (o) enter into any contract, agreement,  commitment or other
binding  arrangement  that would result in a liability  or financial  commitment
which in the aggregate exceeds $25,000, other than amounts reflected on MAA, MAI
or any Subsidiary's capital or operating budgets; or

                    (p) authorize,  recommend,  propose or announce an intention
to do any of the foregoing, or enter into any contract, agreement, commitment or
arrangement to do any of the foregoing.

             Section 5.2   Access  to  Information.   Subject to applicable law,
                           -----------------------
Seller,  MAA and MAI will  give AMSC and  Purchaser,  their  counsel,  financial
advisors, auditors and other authorized representatives reasonable access during
business hours after  reasonable  notice to the offices,  properties,  books and
records  of MAA,  MAI  and  each  of the  Subsidiaries  and  will  instruct  the
employees,   counsel  and  financial  advisors  of  Seller,  MAA,  MAI  and  the
Subsidiaries  to cooperate with AMSC and Purchaser in  theinvestigation  of MAA,
MAI and the Subsidiaries.


             Section 5.3  Efforts; Further Assurances; Permits.
                          ------------------------------------

                    (a) Subject to the terms and  conditions of this  Agreement,
each party will use all commercially  reasonable efforts to take, or cause to be
taken,  all  actions  and to do, or cause to be done,  all things  necessary  or
desirable under  applicable laws and regulations to consummate the  transactions
contemplated by this Agreement,  including,  without  limitation,  preparing and
making any filings required to be made under applicable law. Each of the parties
shall furnish to the other parties such  necessary  information  and  reasonable
assistance as such other party may request in connection with the foregoing.

                    (b) In case at any time after the  Closing  Date any further
action is necessary  or  desirable to carry out the purposes of this  Agreement,
AMSC,  Purchaser  and Seller shall,  and Seller shall cause the proper  officers
and/or directors of MAA, MAI and the Subsidiaries to, take all such necessary or
desirable action.

                    (c) Upon AMSC's or Purchaser's request, Seller will use, and
will cause MAA, MAI and the Subsidiaries to use, commercially reasonable efforts
to assist  AMSC and  Purchaser  in  obtaining  any  permits,  licenses  or other
authorizations  necessary for AMSC's and  Purchaser's  operation of MAA, MAI and
the Subsidiaries consistent with past practice after the Closing Date.

                    (d) In the event  that at any  time,  any  order,  decree or
injunction  shall be entered which prevents or delays the consummation of any of
the transactions  contemplated by this Agreement,  each party shall promptly use
its best  efforts to cause such  order,  decree or  injunction  to be  reversed,
vacated  or  modified  in  order to  permit  such  transactions  to  proceed  as
expeditiously as possible.

             Section 5.4 Books and Records.  AMSC, Purchaser and Seller agree to
                         -----------------  
retain for a period of three years or longer if otherwise  required by law after
the Closing  Date,  any and all Books and  Records  (hard  copy,  electronic  or
otherwise)  related to MAA, MAI and the  Subsidiaries  and in the  possession of
Seller, MAA, MAI or the Subsidiaries for all periods through the Closing Date or
related to the transactions contemplated hereby.  Notwithstanding the foregoing,
either  party may  notify the other of its desire to  discontinue  retention  of
specified documents in accordance with applicable record retention  requirements
during such period upon thirty days' written  notice and such party may elect to
assume  custody  thereof.  In the event any party needs access to such Books and
Records for purposes of verifying any representations  and warranties  contained
in  this  Agreement,   responding  to  inquiries  from  Governmental   Entities,
indemnifying, defending and holding harmless other parties hereto, in accordance
with applicable  provisions of this Agreement or any other  legitimate  business
purpose,  each party will allow  representatives  of the other parties access to
such books and records upon reasonable  notice during regular business hours for
the sole purpose of obtaining  information  for use as aforesaid and will permit
such other party to make such extracts and copies thereof as may be necessary or
convenient  and, if required for such purpose,  to have access to and possession
of original documents. 

Within 15  Business  Days  after the  Closing  Date,  Seller  shall  provide  to
Purchaser the Closing Financial Statements.

             Section 5.5  Governmental  Regulatory  Approvals.   As  promptly as
                          -----------------------------------
practicable after the date hereof,  AMSC, Purchaser and Seller shall, and Seller
shall cause MAA, MAI and the Subsidiaries to, file the required applications and
notices with the appropriate Governmental Entities as necessary for consummation
of the transactions contemplated by this Agreement (the "Regulatory Approvals").
To  the  extent   transferable,   Seller  will  transfer  any  existing  Non-FCC
Authorizations to Purchaser. Each party agrees to use its best efforts to obtain
the  Regulatory  Approvals  and the parties  agree to cooperate  fully with each
other and with all Governmental  Entities to obtain the Regulatory  Approvals at
the earliest practicable date.

             Section 5.6  FCC Consent.  As  promptly  as  practicable  after the
                          -----------
execution of this Agreement, the parties shall file all appropriate applications
and requests  with the FCC seeking,  and shall use their best efforts to obtain,
(i) the FCC's consent to the transfer of control of the licensed Subsidiaries to
Purchaser under the FCC Licenses (as listed in Section 3.23(b) of the Disclosure
Schedule),  and (ii) any necessary FCC waivers (all such consents or waivers are
collectively referred to as "FCC Consents").

             Section 5.7 HSR Act Review.  As promptly as  practicable  after the
                         --------------
execution  of this  Agreement,  the  parties  will make such  filings  as may be
required by the HSR Act with respect to the sale contemplated by this Agreement.
Thereafter,  the parties will file as promptly as practicable  any  supplemental
information  that may be requested by the U.S.  Federal Trade  Commission or the
U.S.  Department  of  Justice  pursuant  to the HSR Act.  The  parties  agree to
cooperate in seeking early termination of the waiting periods under the HSR Act.

             Section 5.8  Registration Rights. The Seller and AMSC shall execute
                          -------------------
a registration  rights  agreement,  substantially in the form attached hereto as
Exhibit B (the "Registration Rights Agreement").

             Section 5.9 Lock-up.  Seller hereby agrees not to transfer,  except
                         ------- 
to a  wholly-owned  Affiliate  of Seller  and  except  pursuant  to a  Piggyback
Registration  under the  Registration  Rights Agreement (as defined therein) and
except pursuant to Section 1 of that certain  Participation  Rights Agreement of
even date  herewith,  any  shares of AMSC  Common  Stock now owned or  hereafter
acquired by Seller during the one year period beginning on the Closing Date (the
"Lock-up Period"). Seller further agrees, during the Lock-up Period, not to (nor
will it permit  any  agent or  Affiliate  of Seller  to)  solicit,  initiate  or
encourage any  Acquisition  Proposal or furnish any information to, or cooperate
with,  any  Person,  corporation,  firm,  or other  entity  with  respect  to an
Acquisition Proposal,  unless Seller obtains prior written consent from AMSC. As
used  herein,  "Acquisition  Proposal"  means a  proposal  for a merger or other
business  combination  involving  AMSC or for the  acquisition  of a substantial
equity  interest in, or a  substantial  portion of the assets of,  AMSC.  Seller
shall promptly  communicate to AMSC the terms of any Acquisition  Proposal which
it may receive during such Lock-up Period.

             Section 5.10  Nonsolicitation.  During the period  beginning on the
                           ---------------
date hereof and ending on the  one-year  anniversary  of the  Closing  Date (the
"Nonsolicitation  Period"), Seller shall not, nor shall Seller permit any of its
officers,   directors,   employees,   Person  it   Controls,   agents  or  other
representatives  to,  directly or indirectly,  without prior written  consent of
AMSC,  (i)  actively  solicit  any  employee  of, or (ii)  actively  solicit any
employee who,  within the six months prior to the date of such  solicitation  or
hiring, had been an employee of, MAA, MAI or any of the Subsidiaries unless such
employee's  employment  was  terminated  by or at the request of MAA, MAI or any
Subsidiary.  It is  understood  that generic  advertising  shall not  constitute
"active  solicitation" for purposes of this Section 5.10. AMSC and Purchaser may
seek injunctive relief to prevent any such violations during the Nonsolicitation
Period and also may seek monetary  damages in respect of any  violations of this
Section 5.10.

Nothing in this Section 5.10 shall prevent Seller or any Person it controls from
hiring  any  such  employee  so long as such  hiring  is not the  result  of the
solicitation prohibited under this Section 5.10.

             Section 5.11  IBM Contract Renewal.   Seller shall  deliver to AMSC
                           --------------------
and Purchaser a fully executed  renewal of the services  contract by and between
ARDIS and  International  Business  Machines in  substance  and form  reasonably
satisfactory to Purchaser.


             Section 5.12  UPS  Contract.  Seller  shall  deliver  to  AMSC  and
                           -------------
Purchaser a fully  executed  services  contract by and between  ARDIS and United
Parcel  Service,  substantially  in  substance  and  form as  signed  by UPS and
previously provided to Purchaser (the "UPS Contract").

             Section 5.13  Escrow Agreement.  AMSC,  Purchaser  and Seller shall
                           ----------------
have executed the Escrow Agreement.

             Section 5.14 Employee  Transition.  Purchaser  shall provide,  as a
                          --------------------
general  matter,  compensation,  benefits  and  continued  employment  generally
comparable in the aggregate to those received by the employees of ARDIS prior to
the Closing,  consistent with Purchaser and AMSC's financial,  structuring,  and
organizational  considerations,  including  existing AMSC employee  compensation
considerations.  Promptly after the date hereof and prior to the Closing,  these
compensation  benefits and employment provisions will be presented to Seller. In
the event that  Purchaser  terminates  the  employment of a Management  Employee
within 12 months after the Closing Date, Purchaser shall provide such Management
Employee with the Severance Package (as defined below).  Promptly after the date
hereof and prior to the Closing,  the substantial terms of the severance package
for  Management  Employees  shall (i) be presented  to Seller and be  reasonably
acceptable to Seller and (ii) shall contain standard terms generally  offered to
management employees of similarly situated companies (the "Severance Package").

             Section 5.15   Updated Disclosure Schedule.   From  the date hereof
                            ---------------------------
until the Closing Date,  Seller shall  disclose to Purchaser and AMSC in writing
any material  variances from the  representations  and  warranties  contained in
Article  3 or  Article  8  hereof  promptly  upon  discovery  thereof,  and such
disclosures  shall update the Disclosure  Schedule for purposes of Articles 3, 7
and 8.


             Section 5.16  Nextel Proceeds.   ARDIS  has  entered  into an Asset
                           ---------------

Purchase  Agreement by and between  ARDIS and Nextel West Corp.,  dated July 11,
1997, which provides for the acquisition of certain ARDIS business  assets.  The
right of ARDIS to receive any and all  proceeds  under such  agreement  shall be
deemed for all  purposes to be assigned to Seller and (i) prior to the  Closing,
Seller  shall be entitled to collect and keep such  proceeds for its own account
(and cause ARDIS to cooperate in such regard) and (ii) prior to Closing,  Seller
may cause the Company to assign to Seller for payment from Nextel West Corp. the
proceeds from such agreement.


             Section 5.17 Non-Vendor  Intercompany Financing  Arrangements.  Any
                          ------------------------------------------------
non-vendor  financing  arrangement  existing as of the Closing between Seller or
any Seller Affiliate (other than the Subsidiaries),  on the one hand, and MAA or
MAI, on the other hand, is hereby cancelled and extinguished without any further
obligations related thereto on the part of MAA or MAI. I.

             Section 5.18  Intercompany Agreements.  Notwithstanding anything to
                           -----------------------
the contrary in any agreement between Ardis or Motorola entered into at any time
prior to the Closing Date:

                    (a) For the purpose of each such  agreement,  Seller  hereby
consents to the transactions contemplated by this Agreement.

                    (b) All such  agreements  shall  continue  in full force and
effect notwithstanding the transactions contemplated by this Agreement.  Without
limiting the generality of the foregoing, any provision limiting the application
of any such  agreement to ARDIS while it remains a subsidiary of Seller shall be
without force or effect.

                    (c) After the Closing  Date,  ARDIS may assign or  otherwise
transfer  any or all of its  rights  under  any such  agreements  to AMSC or any
Affiliate of AMSC that holds substantially all the assets of ARDIS, and if ARDIS
does so, such agreements shall continue in full force and effect notwithstanding
such transfer.



                                 ARTICLE 6. CONDITIONS TO CLOSING

             Section 6.1  Conditions to Obligation of Purchaser.  The obligation
                          -------------------------------------
of  Purchaser to purchase  the Shares  shall be subject to the  satisfaction  or
waiver by Purchaser of the following conditions:

                    (a) Representations and Warranties of Seller to be True.
                        ---------------------------------------------------
The  representations and warranties of Seller herein contained shall be true and
correct in all material respects on the date hereof and at the Closing Date with
the same effect as though  made at such time,  except (i) insofar as any of such
representations  and  warranties  are given as of a  particular  date and relate
solely  to a  particular  date or  period,  and (ii) to the  extent  any of such
representations  and  warranties  have been waived  hereunder or affected by the
transactions  contemplated or permitted herein. Seller shall have performed,  or
caused MAA, MAI and the  Subsidiaries to perform,  in all material  respects all
obligations  and  complied  in all  material  respects  with all  covenants  and
conditions  required by this  Agreement to be performed or complied with by them
at or prior to the Closing Date.

                    (b) No  Injunction  or  Other  Governmental  Action.  (i) No
                        -----------------------------------------------
preliminary or permanent  injunction,  decree or other order issued by any court
of competent  jurisdiction  or by any  governmental  or  regulatory  body or any
statute,  rule,  regulation  or executive  order  promulgated  or enacted by any
Governmental  Entity  after  the  date of this  Agreement  which  prohibits  the
consummation of the  transactions  contemplated  hereby shall be in effect;  and
(ii) no governmental  agency or body shall have instituted any suit,  action, or
legal or administrative proceeding to restrain, enjoin or otherwise question the
validity or legality of the  transactions  contemplated by this Agreement and no
order or  decree so  restraining  or  enjoining  such  transactions  shall be in
effect.

                    (c)   Statutory    Requirements;    Regulatory    Approvals;
                          ------------------------------------------------------
Contractual  Consents.  (i) All required waiting periods under the HSR Act shall
- ---------------------
have expired or been  terminated;  (ii) all  Regulatory  Approvals and all other
authorizations,  consents,  orders or approvals of, or  declarations  or filings
with, or expirations or terminations of waiting periods imposed by, the FCC, any
state public  service  commission,  public  utility  commission or similar state
agency,  or other  Governmental  Entities  necessary to effect the  transactions
contemplated by this Agreement shall have occurred,  been filed or been obtained
and become  Final  Orders,  provided,  that nothing in this  paragraph  shall be
deemed to prohibit  Closing upon issuance of the FCC  Authorization  pursuant to
the terms set forth in Section  2.6(a);  and (iii) all other  Required  Consents
shall have been obtained and shall be in full force and effect.

                    (d) Certificate.  Seller shall have delivered to Purchaser a
                        -----------
certificate to the effect that each of the conditions specified above in Section
6.1(a)-(c) has been satisfied in all respects; 

                    (e) Escrow Agreement. Seller and the Escrow Agent shall have
                        ----------------
executed the Escrow Agreement.

                    (f) IBM  Contract  Renewal.  Seller  shall have  delivered a
                        ----------------------
fully  executed  renewal  of the  services  contract  by and  between  ARDIS and
International Business Machines in substance and form reasonably satisfactory to
Purchaser. 

                    (g)  UPS  Contract.  Seller  shall  have  delivered  a fully
                         -------------
executed  services  contract  by and  between  ARDIS and United  Parcel  Service
substantially in substance and form as signed by UPS and previously  provided to
Purchaser.

                    (h) Directors and Non-Employee Officers.  Purchaser and AMSC
                        -----------------------------------
shall have  received  the  resignations,  effective  as of the  Closing,  of all
directors and non-employee officers of MAA, MAI and each of the Subsidiaries.

                    (i) AMSC Shareholder Approval. Purchaser shall have received
                        -------------------------
AMSC Shareholder Approval as and to the extent required.

                      (j)  Deliveries.   All actions to be taken by Seller,  MAA
                           ----------
and MAI in connection with consummation of the transactions  contemplated hereby
and all certificates,  opinions,  instruments,  and other documents  required to
effect the transactions  contemplated hereby will be reasonably  satisfactory in
form and substance to Purchaser.  Each of the deliveries  required under Section
2.7(b) shall have been prepared to the reasonable  satisfaction of Purchaser and
AMSC and their counsel.


                      (k) No  Material  Adverse  Change.  Since the date of this
                          -----------------------------
Agreement, there shall not have been any Material Adverse Change.

                    (l) Financing.  Purchaser shall have obtained,  on terms and
                        ---------
conditions  reasonably  satisfactory  to it,  financing  in the capital  markets
sufficient to consummate the transactions contemplated hereby.


             Purchaser may waive any condition  specified in this Section 6.1 if
Purchaser executes a writing so stating at or prior to Closing.

             Section 6.2  Conditions to Obligations of Seller.   The  obligation
                          -----------------------------------
of Seller to sell the Shares shall be subject to the  satisfaction  or waiver by
Seller of the following conditions:


                    (a)  Representations and Warranties of Purchaser and AMSC to
                         -------------------------------------------------------
Be True.  The  representations  and  warranties  of  Purchaser  and AMSC  herein
- -------
contained shall be true and correct in all material  respects on the date hereof
and at the Closing Date with the same effect as though made at such time, except
(i)  insofar as any of such  representations  and  warranties  are given as of a
particular  date and relate solely to a particular  date or period,  and (ii) to
the extent any of such representations and warranties have been waived hereunder
or affected by the  transactions  contemplated  or  permitted  herein.  AMSC and
Purchaser  shall have  performed in all material  respects all  obligations  and
complied in all material respects with all covenants and conditions  required by
this  Agreement  to be  performed  or  complied  with by them at or prior to the
Closing Date.

                    (b) No  Injunction  or  Other  Governmental  Action.  (i) No
                        -----------------------------------------------
preliminary  or  permanent  injunction  or other  order  issued  by any court of
competent  jurisdiction  or by any  governmental  or  regulatory  body  nor  any
statute,  rule,  regulation  or executive  order  promulgated  or enacted by any
Governmental  Entity  after  the  date of this  Agreement  which  prohibits  the
consummation of the  transactions  contemplated  hereby shall be in effect;  and
(ii) no governmental  agency or body shall have instituted any suit,  action, or
legal or administrative proceeding to restrain, enjoin or otherwise question the
validity or legality of the  transactions  contemplated by this Agreement and no
order or  decree so  restraining  or  enjoining  such  transactions  shall be in
effect.

                    (c) Statutory  Requirements;  Regulatory Approvals.  (i) All
                        ----------------------------------------------
required  waiting  periods  under  the  HSR  Act  shall  have  expired  or  been
terminated;   (ii)  all  Regulatory  Approvals  and  all  other  authorizations,
consents,   orders  or  approvals  of,  or  declarations  or  filings  with,  or
expirations or  terminations  of waiting  periods imposed by, the FCC, any state
public service commission, public utility commission or similar state agency, or
other Governmental Entities necessary to effect the transactions contemplated by
this Agreement shall have occurred, been filed or been obtained and become Final
Orders,  provided,  that nothing in this  paragraph  shall be deemed to prohibit
Closing upon issuance of the FCC  Authorization  pursuant to the terms set forth
in  Section  2.6(a);  and (iii)  all other  Required  Consents  shall  have been
obtained and shall be in full force and effect.

                    (d) Certificate.  Purchaser shall have delivered to Seller a
                        -----------
certificate to the effect that each of the conditions specified above in Section
6.2(a)-(c) has been satisfied in all respects.

                    (e)  Registration  Rights.  AMSC  shall  have  executed  the
                         --------------------
Registration Rights Agreement.

                    (f) Escrow Agreement.  Purchaser,  AMSC and the Escrow Agent
                        ----------------
shall have executed the Escrow Agreement on or prior to the date hereof.

                    (g)  Deliveries.  All actions to be taken by  Purchaser  and
                         ----------
AMSC in connection with consummation of the transactions contemplated hereby and
all certificates,  opinions, instruments, and other documents required to effect
the transactions contemplated hereby will be reasonably satisfactory in form and
substance to Seller.  The  deliveries  required  under Section 2.7(a) shall have
been prepared to the reasonable satisfaction of Seller and its counsel.


                    (h) Minimum  Stock  Price.  The Market  Value of AMSC Common
                        ---------------------
Stock as of the Closing Date shall be at least 70% of the Market Value as of the
date hereof,  after taking into account all stock  splits,  reverse stock splits
and similar adjustments to the number of shares of AMSC Common Stock outstanding
on the date hereof.





                           ARTICLE 7. INDEMNIFICATION

             Section 7.1  Indemnification by Seller.   Seller  shall  indemnify,
                          -------------------------
defend and hold Purchaser and their Affiliates harmless from and against any and
all liabilities,  losses, damages, costs and expenses  (collectively,  "Losses")
asserted against, imposed on, or incurred or suffered by Purchaser,  MAA, MAI or
the Subsidiaries as a result of any of the following:

                    (a) the  inaccuracy of any  representation  or the breach of
any warranty set forth in Article 3 or in any agreement or certificate  executed
and delivered by Seller pursuant to this Agreement;

                    (b)  the   non-fulfillment   of  any  unwaived  covenant  or
agreement on the part of Seller set forth in this  Agreement or in any agreement
or certificate executed and delivered pursuant to this Agreement; and

                    (c)  any  and  all  actions,  suits,  claims,   proceedings,
investigations,  audits, examinations,  demands, assessments,  fines, judgments,
settlements,  interest,  penalties,  costs,  remedial actions and other expenses
(including  without  limitation  reasonable audit,  engineering,  consulting and
legal fees) pertaining to or arising out of any of the foregoing.

             Section 7.2  Indemnification by AMSC.  AMSC shall indemnify, defend
                          -----------------------
and hold Seller and its Affiliates  harmless from and against any and all Losses
asserted  against,  imposed  on,  or  incurred  or  suffered  by  Seller or such
Affiliates as a result of any of the following:

                    (a) the  inaccuracy of any  representation  or the breach of
any warranty set forth in Article 4 or in any agreement or certificate  executed
and delivered by AMSC or Purchaser pursuant to this Agreement;

                    (b) the nonfulfillment of any unwaived covenant or agreement
on the part of AMSC or Purchaser set forth in this Agreement or in any agreement
or certificate executed and delivered pursuant to this Agreement; and

                    (c)  any  and  all  actions,  suits,  claims,   proceedings,
investigations,  audits, examinations,  demands, assessments,  fines, judgments,
settlements,  interest,  penalties,  costs,  remedial actions and other expenses
(including  without  limitation  reasonable audit,  engineering,  consulting and
legal fees) pertaining to or arising out of any of the foregoing.

              Section  7.3   Limitations  on  Indemnification  for  Breaches  of
                             ---------------------------------------------------
Representations and Warranties.
- ------------------------------

             The  following  indemnification   provisions  shall  apply  to  all
breaches of representations,  warranties or covenants by Seller (including those
in Article 8), except those  contained in Sections 3.1, 3.2, 3.3, 3.4, or 3.5 or
as  otherwise  specifically  provided  in this  Agreement,  and all  breaches of
representations,  warranties or covenants of Purchaser and AMSC (including those
in Article 8),  except  those  contained in Sections 4.1 and 4.2 or as otherwise
specifically provided in this Agreement:

                    (a) No Indemnitor shall be liable for indemnification  until
the total amount of Losses  incurred by the  Indemnitee  exceeds  $300,000  (the
"Indemnification   Threshold  Amount")  provided  that  if  the  Indemnification
Threshold  Amount is exceeded with respect to Losses for which an Indemnitor has
an  indemnification  obligation  under  this  Article 7 or  Article 8, then such
Indemnitor's  obligation  shall include the full amount of such Losses as if the
limitation contained in this subsection (a) did not exist.

                    (b) Except as provided under Section  7.3(c),  no Indemnitor
shall be  liable  for  indemnification  payments  under  any  provision  of this
Agreement  to  the  extent  such  aggregate  indemnification  payments  by  such
Indemnitor exceed $10,000,000.

                    (c)  Notwithstanding  any other provision in this Agreement,
there shall be no limit for indemnification  payments with respect to any breach
of the representations  and warranties  contained in Section 3.25 or pursuant to
Section 8.7(i) hereof.

               Section  7.4  Survival of  Representations  and  Warranties.  The
                             ---------------------------------------------
representations  and  warranties of the parties hereto shall survive the Closing
and shall, except as otherwise specifically set forth in this Agreement,  expire
two years after the Closing Date, except as otherwise  specifically  provided in
this  Agreement.   Notwithstanding   the  preceding,   the  representations  and
warranties   set  forth  in  Sections  3.7,  3.8,  3.9,  3.10  (except  for  the
representations  and  warranties  pursuant to the first sentence of such Section
3.10, the survival period of which shall be two years),  3.11, 3.12, 3.13, 3.14,
3.15, 3.17, 3.18, 3.20, 3.24, 3.25, 3.26, 3.27, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8 and
4.9 shall expire one year after the date hereof.

               Section  7.5  Method  of   Asserting   Claims.   All  claims  for
                             -------------------------------
indemnification   by  a  party   entitled  to  be   indemnified   hereunder  (an
"Indemnitee")  by  another  party  hereto (an  "Indemnitor"),  except for claims
relating to Taxes which shall be governed by the  provisions of Article 8, shall
be asserted and resolved as follows:

                    (a) In the  event  that any  claim or  demand  for  which an
Indemnitee  may claim  indemnity  is asserted  against or sought to be collected
from an Indemnitee by a third party,  the Indemnitee shall notify the Indemnitor
within 20 days  following the receipt by the Indemnitee of such claim or demand,
specifying  the nature of such  claim or demand and the amount or the  estimated
amount  thereof  to the  extent  then  feasible  (which  estimate  shall  not be
conclusive  of the final amount of such claim and demand) (the "Claim  Notice").
Failure of an Indemnitee  to so notify an  Indemnitor  within such 20-day period
shall not relieve an  Indemnitor of its  obligation to indemnify the  Indemnitee
for such claim or demand except to the extent that the delay in giving notice of
such claim or demand in fact materially prejudices (i) the defense of such claim
or demand  where the  Indemnitor  has the right to control  such defense or (ii)
participation  in the defense of such claim or demand where the Indemnitor has a
right of  participation.  Any  party  hereto  against  whom a claim or demand is
asserted  by  a  third  party   shall,   without   prejudice  to  any  right  of
indemnification  hereunder,  appropriately  respond  to  such  claim  or  demand
(whether by answer,  denial,  request for  extension of time or other action) to
such claim or demand within any  applicable  time period,  so as to preserve any
rights or remedies it or any other party may have against the person making such
claim or demand.

                    (b) An Indemnitor  shall have thirty (30) days from the date
on which the Claim  Notice is duly  given  (the  "Notice  Period")  to notify an
Indemnitee (i) whether or not it disputes the liability of the Indemnitor to the
Indemnitee  hereunder  with  respect to such claim or demand and (ii) whether or
not the  Indemnitor  desires,  at its  sole  cost and  expense,  to  defend  the
Indemnitee  against such claim or demand.  If an  Indemnitor  does not notify an
Indemnitee  within the Notice  Period  that it  disputes  its  liability  to the
Indemnitee,  the  Indemnitor  shall be liable  for the  amount of any  resulting
Losses.

                    (c) In the event an Indemnitor notifies an Indemnitee within
the Notice Period that it desires to defend the Indemnitee  against such a claim
against or demand from the Indemnitee,  then except as hereinafter  provided the
Indemnitor  shall  defend,  at its sole  cost and  expense,  the  Indemnitee  by
appropriate proceedings,  shall use its best efforts to settle or prosecute such
proceedings  to a final  conclusion in such a manner as to avoid any risk of the
Indemnitee (or MAA, MAI or the  Subsidiaries,  if a Purchaser is the Indemnitee)
becoming  subject to any  injunctive  or other  equitable  order or relief or to
liability for any other  matter,  and shall control the conduct of such defense;
provided,  however,  that the  Indemnitor  shall not,  without the prior written
consent of the  Indemnitee,  consent to the entry of any  judgment  against  the
Indemnitee or enter into any settlement or compromise which does not include, as
an  unconditional  term thereof,  the giving by the claimant or plaintiff to the
Indemnitee of a release,  in form and substance  reasonably  satisfactory to the
Indemnitee,  from all liability in respect of such claim or  litigation.  If the
Indemnitee  desires to  participate  in, but not  control,  any such  defense or
settlement, it may do so at its sole cost and expense.

                    (d) Prior to an  Indemnitor's  settling  any claim or demand
the defense of which it has assumed  control,  the  Indemnitor  shall obtain the
Indemnitee's  approval,  confirmed  in  writing  in  accordance  with the notice
provisions hereof, which approval shall not be unreasonably withheld or delayed.
If an Indemnitee  notifies an Indemnitor of its disapproval of such  settlement,
the Indemnitee  shall  thereupon  become liable,  from and after the date of its
disapproval, for the amount of any award, judgment, costs or expenses (including
attorney  fees) in excess of the proposed  settlement  amount and shall have the
right  to  elect to  control  the  defense  of such  claim at its sole  cost and
expense.

                    (e) In the event an  Indemnitee  should have a claim against
an Indemnitor  hereunder which does not involve a claim or demand being asserted
against  or sought  to be  collected  from the  Indemnitee  (or MAA,  MAI or the
Subsidiaries, if a Purchaser is the Indemnitee) by a third party, the Indemnitee
shall promptly send a Claim Notice with respect to such claim to the Indemnitor.
If the Indemnitor  does not notify the Indemnitee  within the Notice Period that
it disputes  such claim,  the  Indemnitor  shall be liable for the amount of any
resulting Losses.

             Section  7.6  Method of  Payment.  Any  indemnification  payment by
                           ------------------
Purchaser  to Seller  pursuant  to this  Article 7 or Article 8 shall be made in
immediately available funds. Any indemnification  payment by Seller to Purchaser
pursuant to this Article 7 or Article 8 shall be made (i) first,  in AMSC Common
Stock received by Seller  pursuant to this  Agreement,  and (ii) second,  to the
extent such indemnification payment amount exceeds the aggregate Market Value of
the AMSC Common Stock held by Seller, in immediately available funds;  provided,
however,  that any indemnification  payments by Seller to Purchaser with respect
to any breach of the representations and warranties contained in Section 3.25 or
pursuant to Section 8.7(i) shall be made in  immediately  available  funds.  For
purposes  of  any  indemnification  payment  made  by  Seller  pursuant  to  the
immediately preceding sentence,  the Market Value of the AMSC Common Stock shall
be calculated  as the higher of (A) the Market Value as of the date hereof,  and
(B) the Market Value as of the date of such indemnification payment.

             Section 7.7  Limitation of Recourse.
                          ----------------------

                    (a)  Following  the  Closing,  except with respect to claims
based upon fraud, the  indemnification  provided by Article 7 or Article 8 shall
be the sole and exclusive remedy for any Losses of any party hereto with respect
to any  misrepresentation or inaccuracy in, or breach of, any representations or
warranties  or any  breach or  failure  in  performance  prior to Closing of any
covenants or agreements made by any party in this Agreement or in any exhibit or
schedules hereto or any certificate delivered hereunder.

                    (b) No  claim  shall be  brought  or  maintained  by AMSC or
Purchaser  or their  respective  successors  or  permitted  assigns  against any
officer,  director or employee  (present or former) of any of the  Companies  or
Seller,  or by Seller or its respective  successors or permitted assigns against
any officer,  director or employee (present or former) of Purchaser or AMSC, and
no recourse shall be brought or granted  against any such persons,  by virtue of
or based upon any alleged misrepresentation or inaccuracy in or breach of any of
the  representations,  warranties or covenants of any of the Companies or Seller
on the one hand, or Purchaser or AMSC on the other hand,  set forth or contained
in this Agreement or any exhibit or schedule hereto or any certificate delivered
hereunder,  except to the  extent  that the same  shall  have been the result of
fraud by any such Person (and in the event of such fraud, such recourse shall be
brought or granted solely against the Person or Persons committing such fraud).

             Section 7.8  Acknowledgment by Seller,  Purchaser and AMSC. Seller,
                          ---------------------------------------------
Purchaser  and  AMSC  each  hereby  acknowledges  that it has  conducted  to its
satisfaction,  an independent  investigation  and  verification of the financial
condition, results of operations, assets, liabilities,  properties and projected
operations  of  AMSC  and  the  Companies,  respectively,  and in  making  their
respective  determination to proceed with the transactions  contemplated by this
Agreement,  (i)  Seller  has  relied  on  the  results  of its  own  independent
investigation  and verification and the  representations  and warranties of AMSC
and Purchaser  expressly and specifically set forth in this Agreement,  and (ii)
Purchaser  and AMSC have each  relied on the  results  of their own  independent
investigation and verification and the  representations and warranties of Seller
and the Companies  expressly and specifically set forth in this Agreement.  SUCH
REPRESENTATIONS  AND WARRANTIES BY SELLER AND THE COMPANIES ON THE ONE HAND, AND
BY AMSC AND  PURCHASER  ON THE OTHER  HAND,  CONSTITUTE  THE SOLE AND  EXCLUSIVE
REPRESENTATIONS  AND  WARRANTIES  OF  SUCH  PARTIES  TO  THE  OTHER  PARTIES  IN
CONNECTION  WITH  THE   TRANSACTIONS   CONTEMPLATED   HEREBY,   AND  EACH  PARTY
UNDERSTANDS,   ACKNOWLEDGES  AND  AGREES  THAT  ALL  OTHER  REPRESENTATIONS  AND
WARRANTIES  OF ANY KIND OR  NATURE  EXPRESSED  OR  IMPLIED  (INCLUDING,  BUT NOT
LIMITED  TO, ANY  RELATING  TO THE  FUTURE OR  HISTORICAL  FINANCIAL  CONDITION,
RESULTS OF OPERATIONS,  ASSETS OR LIABILITIES OF THE COMPANIES) ARE SPECIFICALLY
DISCLAIMED BY SELLER AND THE COMPANIES AND OF AMSC ARE  SPECIFICALLY  DISCLAIMED
BY AMSC AND PURCHASER.


                             ARTICLE 8. TAX MATTERS

             Section 8.1   Seller's Tax Representations and Warranties.   Seller
                           -------------------------------------------
hereby represents and warrants to AMSC that:

                    (a)  For the  period  from  its  incorporation  through  the
Closing  Date,  MAI was and will remain a member of the Seller Group and was and
will be included in the  consolidated  federal  income tax returns of the Seller
Group.

                    (b)  For the  period  from  its  incorporation  through  the
Closing  Date,  MAA was and will remain a member of the Seller Group and was and
will be included in the  consolidated  federal  income tax returns of the Seller
Group.

                    (c) For the period from their formation  through the Closing
Date,  each of ARDIS  Holding  and ARDIS was and will remain a  partnership  for
federal and State income Tax purposes.

                    (d) Except as set forth on Section  8.1(d) of the Disclosure
Schedule,  all Tax Returns  required to have been filed by the Companies and any
affiliated, consolidated, combined, unitary or other groups of which any Company
is, will be (at any time on or prior to the  Closing  Date) or was a member have
been or will be filed  timely  and are or will be  accurate  and  correct in all
material respects insofar as they relate to the Companies,  and, insofar as they
relate to the Companies,  all Taxes due and payable (for taxable  periods ending
on or before the Closing Date and for that portion of any Split Period ending on
the Closing  Date) by any Company and any  affiliated,  consolidated,  combined,
unitary  or other  groups of which any  Company  is,  will be (at any time on or
prior to the Closing Date) or was a member (i) have been or will be paid or (ii)
adequate  reserves and/or  liabilities have been or will be established for such
Taxes on the financial books and records of the Companies.

                    (e) Each of the Companies has  established  (and through the
Closing Date will  establish) on its Financial  Statements  and other  financial
books and records reserves and/or  liabilities that are adequate for the payment
of all Taxes not yet due and payable for taxable periods ending on or before the
Closing  Date and for that  portion of any Split  Period  ending on the  Closing
Date.

                    (f) Prior to the Closing Date,  each of the  Companies  will
pay Taxes at such  times  and in such  manner  as are  consistent  with its past
practices.

                    (g) Except as set forth on Section  8.1(g) of the Disclosure
Schedule, no waivers of statutes of limitation have been given or requested with
respect to any Tax  Returns  covering  any  Company or any Taxes  payable by any
Company.

                    (h) Except as set forth on Section  8.1(h) of the Disclosure
Schedule or for matters that have been resolved, no deficiency or adjustment for
any unpaid Taxes of any Company has been proposed, asserted or assessed.

                    (i) There are no Liens  with  respect to Taxes  (except  for
such Liens for Taxes as are disclosed in Section 3.12 of the Disclosure Schedule
and except for Liens for Taxes,  assessments or other  governmental  charges not
yet delinquent) upon any of the properties or assets,  real,  personal or mixed,
tangible or intangible, of the Companies.

                    (j) Except as set forth on Section  8.1(j) of the Disclosure
Schedule,  no Company (i) is or will become a party to any  agreement  providing
for the allocation or sharing of, or  indemnification  for, Taxes, or (ii) is or
prior to the Closing will become required to include in income any adjustment in
tax periods  ending  after the Closing  Date  pursuant to Section  481(a) of the
Code.

                    (k) No  formal  or  informal  plan of  liquidation  has been
adopted by any Company.

                    (l) Except as set forth on Section  8.1(l) of the Disclosure
Schedule,  neither Seller nor any Company:  (i) has filed a consent  pursuant to
Section 341(f) of the Code or agreed to have Section 341(f)(2) of the Code apply
to any disposition of a subsection (f) asset (as such term is defined in Section
341(f)(4) of the Code) owned by a Company; and (ii) has executed or entered into
a closing agreement  affecting a Company pursuant to Section 7121 of the Code or
any predecessor  provision thereof or any similar  provision of State,  local or
foreign law.

                    (m)  Within   twenty  (20)  days  after  the  date  of  this
Agreement,  Seller shall  provide to AMSC a schedule of all tax  elections  that
have been made with  respect to any Company (or any  predecessor  thereof)  that
would have any effect on such Company after  December 31, 1996,  but only to the
extent that such elections were made  affirmatively  by the filing of a separate
document  evidencing  any such  election.  In  addition,  Seller  shall  use all
commercially  reasonable  efforts to  identify  to AMSC in writing  within  such
twenty  (20)  day  period  any  other  such  tax  elections  that  were not made
affirmatively  by  the  filing  of  a  separate  document  evidencing  such  tax
elections.

                    (n) Except as set forth on Section  8.1(n) of the Disclosure
Schedule,  neither  Seller nor any Company has  received  written  notice to the
effect that the  Company is subject to any  penalty by reason of a violation  of
any Tax order, Tax rule or Tax regulation or with respect to any Tax Return.


               Section  8.2  AMSC's Tax  Representations  and  Warranties.  AMSC
                             --------------------------------------------
hereby represents and warrants to Seller that:

                    (a)  Except  for  any   transaction   contemplated  by  this
Agreement (e.g., an election under Section  338(h)(10) of the Code),  AMSC shall
cause the Companies not to engage in any transaction outside the ordinary course
of  business on the Closing  Date after the  Closing if such  transaction  would
increase  the tax  liability  of any of the  Companies  for any Taxable  Year or
portion  thereof ending on the Closing Date.  AMSC and Seller agree to treat any
transaction  of the  Companies  which is (i) - - outside the ordinary  course of
business and (ii) occurs on the Closing Date but after the Closing as occurring,
for federal  income Tax purposes,  at the beginning of the day after the Closing
Date, in accordance with Treasury Regulations Section 1.1502-76(b)(1)(ii)(B).

                    (b) To the  knowledge of AMSC,  the fair market value of the
shares of AMSC Common Stock and other consideration  received by Seller pursuant
to the Merger will be  approximately  equal to the fair market  value of the MAA
Shares surrendered pursuant to the Merger in exchange therefor.

                    (c) To the knowledge of AMSC, following the Merger, MAA will
hold at least 90 percent of the fair market value of Merger Sub's net assets and
at least 70 percent of the fair market  value of Merger  Sub's gross assets held
immediately prior to the Merger.  For purposes of this  representation,  amounts
used by Merger Sub to pay Merger-related  expenses will be included as assets of
Merger Sub immediately prior to the Merger.

                    (d) Immediately prior to the Merger, AMSC will be in control
of Merger Sub within the meaning of Section 368(c) of the Code.

                    (e) AMSC has no plan or intention  to  reacquire  any of the
shares of AMSC Common Stock issued in the Merger.

                    (f)  As of the  date  of  this  Agreement  and at all  times
through and including the effective time of the Merger, AMSC had and has no plan
or intention of causing or permitting  MAA to issue  additional  shares of stock
that would result in AMSC (or any permissible transferee thereof) losing control
of MAA within the meaning of Section  368(c) of the Code.  Except as provided in
the next  sentence,  at any time during the eighteen  (18) months  following the
Closing Date, if AMSC causes or permits MAA to issue additional  shares of stock
such that AMSC (or any  permissible  transferee  thereof)  loses  control of MAA
within the  meaning of Section  368(c) of the Code,  AMSC  shall,  prior to such
issuance,  provide an opinion of Arnold & Porter,  or other  counsel  reasonably
acceptable to Seller, that such issuance of additional shares will not cause the
Merger  to  fail  to  qualify  as  a  tax-free   reorganization   under  Section
368(a)(2)(E)  of the Code. The second  sentence of this Section 8.2(f) shall not
apply if, prior to such issuance of additional  shares of MAA stock,  Seller and
its  Affiliates do not own at least fifty percent (50%) of the AMSC Common Stock
received  by  Seller in the  Merger.  (g) AMSC has no plan or  intention  (i) to
liquidate  MAA,  (ii) to sell or otherwise  dispose of the MAA Shares except for
transfers of such shares to  corporations  controlled by AMSC, or (iii) to cause
MAA to sell or  otherwise  dispose  of any of its assets or of any of the assets
acquired from Merger Sub, except for dispositions made in the ordinary course of
business or transfers of assets to a  corporation  controlled  by MAA within the
meaning of Section 368(c) of the Code.

                    (h) Merger Sub will have no liabilities  assumed by MAA, and
will not transfer to MAA any assets subject to liabilities, in the Merger.

                    (i)  Following  the Merger,  MAA will  continue its historic
business  or use a  significant  portion of its  historic  business  assets in a
business.

                    (j) AMSC and Merger Sub will pay their respective  expenses,
if any, incurred in connection with the Merger.

                    (k) There is no intercorporate indebtedness existing between
AMSC and MAA or between Merger Sub and MAA that was issued, acquired, or will be
settled at a discount.

                    (l) AMSC does not own, nor has it owned during the past five
years, any shares of the stock of MAA.

                    (m) Neither AMSC nor Merger Sub is an investment  company as
defined in Section 368(a)(2)(F)(iii) and (iv) of the Code.

                    (n) AMSC shall cause each of the  representations  contained
in Section  8.2(a)  through  (m) to be true  through the  effective  time of the
Merger.

               Section 8.3 Tax Returns, Audits, Contests, Etc.; Tax Cooperation;
                           -----------------------------------------------------
Tax Sharing Agreements; Tax Records.
- -----------------------------------

                    (a)  Seller  shall  prepare  and file  timely or cause to be
prepared  and filed  timely (i) all Tax Returns of or  including  any Company or
Benefit Plan for any Taxable Year  (including  any Short  Taxable  Year) the due
date (including extensions) for which is on or before the Closing Date, (ii) the
federal income Tax Returns of the Companies (e.g., Forms 1065 and separate Forms
1120 for inclusion in the consolidated  federal income Tax Returns of the Seller
Group) for any Taxable Year - - (including  any Short Taxable Year) ending on or
before  the  Closing  Date,  and  (iii)  all Tax  Returns  for  any  affiliated,
consolidated,  combined,  unitary or other group of which any Company is, was or
will be a member  prior to the  Closing  Date  (other  than any Tax Return for a
Taxable Year ending after the Closing Date for such a group that consists solely
of two or more of the  Companies).  In addition  to the Tax  Returns  that it is
required to file under the  immediately  preceding  sentence,  Seller may, on or
before the Closing Date, file any Tax Return of or including any Company for any
Taxable  Year  (including  any Short  Taxable  Year)  that ends on or before the
Closing Date.

                    (b) (i) AMSC shall be responsible  for the  preparation  and
filing of all Tax Returns of the Companies that are due  (including  extensions)
after the Closing  Date,  other than (A) Tax Returns  that Seller is required to
file under the first  sentence of Section 8.3(a) and (B) Tax Returns that Seller
has filed on or before the  Closing  Date  pursuant  to the second  sentence  of
Section 8.3(a), provided, however, that AMSC shall have no obligation to prepare
any Tax Return for any affiliated, consolidated, unitary or other group of which
any  Company is, was or will be a member  prior to the Closing  Date (other than
any Tax Return that is due  (including  extensions)  after the Closing  Date for
such a group that consists solely of two or more of the Companies).

                         (ii) At the Closing,  Seller shall  provide AMSC with a
list of all unfiled Tax Returns for or including  any Company for Taxable  Years
ending on or before the Closing Date.

                         (iii) If, pursuant to Section 8.7(a),  Seller is liable
to  indemnify  AMSC for any Taxes shown on a Tax Return that AMSC is required to
file under Section 8.3(b)(i), AMSC shall use all commercially reasonable efforts
to provide  Seller with a copy of any such Tax Return  (along with a computation
of the amount of Tax shown on such Tax Return for which Seller is responsible) a
reasonable  time prior to the filing  thereof.  AMSC shall use all  commercially
reasonable  efforts to provide  any such  income Tax Return at least  sixty (60)
days prior to the due date thereof.  AMSC will consider any  suggestion  made by
Seller with respect to the calculations and positions taken in such Tax Returns.
Failure by AMSC to comply with the provisions of this Section  8.3(b)(iii)  will
in no way eliminate, limit or restrict Seller's indemnification  obligations set
forth in Section 8.7.

                    (c) (i)  Seller  shall pay or cause to be paid (A) all Taxes
of the Companies or Taxes for which any Company may be liable that are due on or
before the  Closing  Date,  and (B) the federal  and State  income  Taxes of the
Companies for any Taxable Year  (including  any Short Taxable Year) ending on or
before the Closing Date.

                         (ii) No later than 180 days following the Closing Date,
AMSC  shall  provide  to Seller a federal  income Tax  computation  and  related
schedules  and data for each Company  having a Short  Taxable Year ending on the
Closing Date,  which Tax computation  shall be consistent with Tax Returns filed
for prior  Taxable  Years and shall  reflect  the  income,  gain or loss of such
Company for that Short Taxable Year other than any income,  gain or loss arising
or resulting from any election described in Section 8.4.

                         (iii)  Seller  shall  use all  commercially  reasonable
efforts to complete  prior to the Closing Date all necessary  federal income Tax
computations  and related  schedules  and data for each  Company for the Taxable
Years of the Companies  ending on December 31, 1997. To the extent necessary for
Seller to  complete  such  computations,  schedules  and data,  AMSC shall allow
Seller and its agents  reasonable access after the Closing Date to the books and
records of the Companies.

                         (iv)  Except as  provided  in Section  8.3(c)(i),  AMSC
shall pay or cause to be paid all Taxes of the Companies  that are due after the
Closing Date.

                         (v) The  provisions of this Section 8.3(c) shall not be
construed  or applied to limit or broaden  the  indemnification  obligations  of
either Seller or AMSC under Section 8.7 except as specifically provided therein.
All Tax Returns and computations referred to in this Article 8 shall be prepared
in a manner  consistent with prior Tax Returns,  insofar as such Tax Returns and
computations referred to in this Article 8 relate solely to the Companies.

                    (d) AMSC and Seller  shall use all  commercially  reasonable
efforts to provide each other with copies of Tax Returns  (including amended Tax
Returns)  of or  including  any  Company to the extent any such Tax  Returns are
relevant  in  determining  either  party's  obligations  under  this  Agreement,
including,  but not limited to, the  indemnification  obligations in Section 8.7
and the  procedural  obligations  in this Section 8.3.  The  provisions  of this
Section  8.3  shall  not be  construed  or  applied  to  limit  or  broaden  the
indemnification obligations of either Seller or AMSC under Section 8.7 except as
specifically provided therein.

                    (e)  Seller  and AMSC  shall  provide  prior  notice to, and
cooperate fully with,  each other in connection  with any audit  examinations of
any Company by any  governmental  taxing  authority  with  respect to any Taxes,
including  but not limited to the  furnishing  or making  available  of records,
books of account or other  materials  reasonably  necessary  or helpful  for the
defense  against  the  assertions  of any  taxing  authority  as to any Taxes or
deficiencies thereof.

                    (f) Seller and AMSC shall  cooperate  with one  another  and
their respective  representatives,  in a prompt and timely manner, in connection
with the preparation, signing, and filing of, and any administrative or judicial
proceeding involving, any Tax Return filed or required to be filed by or for (i)
the Seller  Group,  any member  thereof,  or any Company  for any  Taxable  Year
(including any Short Taxable Year) ending on or before the Closing Date, or (ii)
the AMSC  Group,  any  member  thereof,  or any  Company  for any  Taxable  Year
(including  any Short Taxable Year) ending after the Closing Date,  with respect
to any item or issue  affecting the property or operations of any Company.  Such
cooperation shall include,  but not be limited to, making available to the other
party,  during normal business hours,  all books,  records  (including,  but not
limited to, working papers and schedules),  information,  officers and employees
(without  substantial  interruption  of  employment)  reasonably  requested  and
necessary or useful in connection  with any Tax inquiry,  audit,  investigation,
dispute,  litigation  or any other  matter  requiring  any such books,  records,
information,   officers  or  employees  for  any  reasonable  business  purpose.
Notwithstanding the foregoing, neither party shall be required to furnish to the
other Tax Returns or drafts thereof of the Seller Group,  the AMSC Group, or any
affiliated,  consolidated, combined, unitary or other group of which any Company
is, will be or was a member,  as the case may be, for any Taxable  Year,  except
that each party shall furnish to the other the  applicable  portions of such Tax
Returns reporting the operations of the Companies and the applicable portions of
all reports  relating to the examination by the IRS or any other federal,  State
or local governmental  agency. Any information obtained pursuant to this Article
8 shall be held in strict confidence and shall be used solely in connection with
the reason for which it was requested.

                    (g) As of the  Closing  Date,  any and all  Tax  sharing  or
allocation  agreements shall terminate as between any Company,  on the one hand,
and  Seller  or any  Affiliates  thereof,  on the  other  hand,  for  all  Taxes
regardless  of the  Taxable  Year for  which  such  Taxes are  imposed,  and the
provisions of this Agreement shall apply thereafter.

                    (h) (i) AMSC  shall  not,  and  shall not  permit  any other
person or entity to, dispose of or destroy any of the business records and files
of any Company in existence on the Closing Date  relating to Taxes without first
offering to turn over  possession  thereof to Seller by written notice to Seller
at least 30 days prior to the proposed date of such disposition or destruction.

                         (ii) Seller  shall not,  and shall not permit any other
person or entity to,  dispose  of or  destroy  any  business  records  and files
relating  to Taxes of any  Company  now in the  possession  of, or  subsequently
acquired by, either  Seller,  any member of the Seller Group or any Affiliate of
Seller without first offering to turn over possession thereof to AMSC by written
notice to AMSC at least 30 days prior to the proposed  date of such  disposition
or destruction.

             Section 8.4  Asset Purchase Treatment for MAI Shares.
                          ---------------------------------------

                    (a) (i) At the sole  election of  Purchaser,  Purchaser  and
Seller  shall elect for federal Tax  purposes to treat the  purchase and sale of
the MAI Shares  pursuant to this  Agreement as a purchase and sale of the assets
of MAI in accordance  with the provisions of Code Section 338 generally and Code
Section 338(h)(10) specifically. If an election is to be made as provided in the
preceding  sentence,  Purchaser  and Seller  agree to make timely all  elections
necessary to carry out the  provisions  of this Section  8.4(a)(i) and to report
the purchase and sale of the MAI Shares  consistent with the preceding  sentence
and in accordance with the provisions of this Article 8.

                         (ii) If  Purchaser  and  Seller  make the  election  in
Section  8.4(a)(i),  then Purchaser and Seller shall elect, for State income Tax
purposes,  to treat the  purchase  and sale of the MAI Shares as a purchase  and
sale of the assets of MAI to the  extent  permitted  by  applicable  law.  If an
election is to be made as  provided in the  preceding  sentence,  Purchaser  and
Seller agree to make timely all elections  necessary to carry out the provisions
of this Section 8.4(a)(ii) and to report the purchase and sale of the MAI Shares
consistent with the preceding  sentence and in accordance with the provisions of
this  Article 8. In any  State(s)  where it is unclear  whether  applicable  law
permits the  purchase and sale of the MAI Shares to be treated as a purchase and
sale of assets, Purchaser and Seller agree to treat the purchase and sale of the
MAI Shares as a purchase and sale of the assets of MAI provided  that Seller and
Purchaser otherwise make the election described in Section 8.4(a)(i).

                         (iii) The  provisions of Section  8.4(b),  (c), (d) and
(e) below shall apply if Seller and  Purchaser  make an  election  described  in
Section 8.4(a)(i) or (ii).

                    (b) Seller  shall pay or  otherwise be liable for (and shall
indemnify and hold harmless AMSC, its  subsidiaries  and the Companies  against)
any and all Taxes and Other Tax Costs  attributable to the recognition of income
by Seller or any Company  (and  Seller  shall  receive the tax benefit  from any
loss)  from  the  treatment  of the  purchase  and sale of the MAI  Shares  as a
purchase  and sale of the assets of MAI in  accordance  with the  provisions  of
Section 8.4(a).

                    (c)  Purchaser and Seller hereby agree to determine the fair
market value of the assets,  both  tangible and  intangible,  of MAI (and of any
partnership Affiliates of MAI and MAA) (the "Assets") for purposes of allocating
the  consideration  to be paid for, and the amount  realized on the sale of, the
Assets. This determination,  which shall be binding upon Purchaser and Seller in
accordance with the provisions of Section 1060(a) of the Code,  shall be made as
follows:

                         (i) No later  than  sixty (60) days (or such later date
as the parties mutually agree) following the Closing Date, Purchaser shall cause
an appraiser (the "Appraiser"),  which shall be reasonably acceptable to Seller,
to provide to Purchaser and Seller an appraisal of the fair market valuations of
the Assets (the  "Appraisal").  For purposes of this Section  8.4(c),  the "fair
market  value" of an Asset shall mean the amount a willing  buyer would pay to a
willing  seller for the actual  property in question (and not  calculated  based
solely  upon  the  replacement  cost  for  such  property)  in an  arm's  length
transaction  where  each  party to the  transaction  has full  knowledge  of all
relevant information concerning such property.

                         (ii) Each of  Seller  and  Purchaser  may  provide  the
Appraiser  with such  information as it believes will be useful to the Appraiser
in preparing  the  Appraisal.  Copies of any written  materials  provided to the
Appraiser by either Seller or Purchaser shall  simultaneously be provided to the
other party.  All oral  communication  with the Appraiser  shall be made through
Purchaser, which shall provide Seller with reasonable opportunities to speak and
meet with the  Appraiser  to express any views  Seller  reasonably  believes are
pertinent to the preparation of the Appraisal.

                         (iii)   Purchaser  shall  pay  the  basic  fee  of  the
Appraiser as set at the time the Appraiser is initially engaged by Purchaser. To
the extent that any additional  fees, costs or expenses are incurred as a result
of documents provided by Seller,  communications initiated by Seller or meetings
held at Seller's request, Seller shall pay such fees, costs or expenses.

                         (iv)  The  fair   market   valuations   of  the  Assets
determined  by the Appraiser  pursuant to this Section  8.4(c) shall be the fair
market  valuations  of the Assets  for Tax  purposes  and shall be binding  upon
Seller and Purchaser as provided in this Agreement.

               (d) Neither  Seller nor  Purchaser nor any Affiliate of Seller or
Purchaser  shall take a position in any Tax  proceeding,  Tax audit or otherwise
inconsistent  with the fair market  value  determinations  described  in Section
8.4(c);  provided,  however,  that (i) nothing  contained  herein shall  require
Seller or Purchaser to contest any  challenge to such  determinations,  and (ii)
nothing  contained  herein  shall  prevent  Seller,  Purchaser,  or any of their
Affiliates  from  filing  protective  amended  Tax Returns or claims for refunds
after a Tax authority has challenged such determinations.  In the event that any
claim shall be made by any taxing  authority  against  either  Purchaser  or any
Company (or any successor  thereto),  on the one hand,  or Seller,  on the other
hand,  that, if  successful,  would have the effect of altering such fair market
value  determinations,  then  the  party  that  is the  subject  of  such  claim
("Involved  Party") shall give notice thereof to the other party ("Other Party")
in writing  within 30 business days thereof.  Thereafter,  except as provided in
the next sentence, the Involved Party shall have control of any contest relating
thereto,  but the  Involved  Party  shall  consider in good faith any request or
suggestion by the Other Party for any conference, hearing or proceeding relating
to such contest,  shall (to the extent it is feasible to do so) permit the Other
Party to participate  therein at such Other Party's expense and shall not object
to such  Other  Party's  submission  of briefs  and  memoranda  of law  relating
thereto,  and  shall  provide  the Other  Party  with any  relevant  information
reasonably requested by such Other Party.  Notwithstanding the provisions of the
preceding  sentence,  the Other Party shall have control of any contest relating
to the fair market valuations if the Involved Party has notified the Other Party
that the  Other  Party is  obligated  under the  provisions  of  Section  8.7 to
indemnify  the  Involved  Party for any Tax  liability  relating to the proposed
adjustments  to the fair  market  valuations  and the  Other  party  shall  have
provided  to the  Involved  Party  the  written  notice  and  acknowledgment  of
financial responsibility referred to in the first sentence of Section 8.7(g).

               (e)  Purchaser  and Seller  each  agrees to prepare  and file all
Internal  Revenue  Service  forms and the  required  schedules  thereto  and all
requisite State and local forms and schedules  ("Forms") required to be filed by
either or both of them  providing  for the treatment of the purchase and sale of
the MAI  Shares as  purchases  and sales of the  Assets in  accordance  with the
provisions of Section 8.4(a). Purchaser shall request in writing from Seller, or
Seller shall  request in writing from  Purchaser,  any  information  (reasonably
within the knowledge or possession of the person from whom requested)  necessary
to complete the Forms, which information shall be provided no later than 30 days
following any such request. All such Forms shall be prepared consistent with the
fair market valuations of the Assets determined under Section 8.4(c),  provided,
however,  that Seller and Purchaser each recognize that appropriate  adjustments
will be made for  transaction  and other costs and as required by any applicable
laws or regulations in determining  the amount  realized upon the disposition of
the Assets or the amount paid for the Assets.

             Section 8.5   Tax-Free Reorganization Treatment for the MAA Merger.
                           ----------------------------------------------------
Seller  and AMSC agree that they  intend  that the Merger  qualify as a tax-free
reorganization  described in Section  368(a)(2)(E)  of the Code,  and Seller and
AMSC  shall  file all Tax  Returns in a manner  consistent  with such  treatment
(including  satisfying  all  reporting  requirements  necessary  to obtain  such
treatment).  Neither  Seller nor AMSC nor any  Affiliate of Seller or AMSC shall
take a position in any Tax proceeding,  Tax audit or otherwise inconsistent with
the  treatment  of the  Merger as a  tax-free  reorganization  qualifying  under
Section  368(a)(2)(E) of the Code;  provided,  however,  that nothing  contained
herein  shall  prevent  Seller,  AMSC,  or any of their  Affiliates  from filing
protective  amended Tax Returns or claims for refund after a Tax  authority  has
challenged such treatment.

             Section 8.6  Transfer Taxes.  Notwithstanding  any other  provision
                          --------------
in this  Agreement,  Seller  and  AMSC  shall  each be  responsible  for and pay
one-half of any transfer  taxes,  recording  taxes,  bulk sale taxes and similar
transaction taxes resulting from the transfer of the MAI Shares,  the MAA Shares
or the deemed  transfer of the equity  interests in or the assets of any Company
as a result of the  transactions  contemplated  by this  Agreement.  Each  party
hereto hereby shall pay all such taxes and file all necessary  documentation  as
required  under the  applicable  statutory  provisions  with respect to all such
taxes in a timely  manner.  Not later than fifteen (15) business days  following
receipt  of  written  notice  from  AMSC or  Seller  that it has paid any  Taxes
described  in this  Section  8.6,  the  other  party  shall pay to the payor its
one-half share of such Taxes.

             Section  8.7  General Tax Indemnifications.
                           ----------------------------

               (a)  Seller  shall  indemnify  and  hold  harmless  AMSC  and its
Affiliates  (including  the  Companies)  from and against any and all Taxes with
respect to which any Company or any entity as successor thereto may be liable to
the extent  such  Taxes are (i)  attributable  to any breach of any of  Seller's
representations,  warranties  or  covenants  contained  in this  Article 8, (ii)
payable with respect to any Taxable Year ending on or prior to the Closing Date,
or (iii)  payable with respect to that portion of any Split Period that is prior
to and including the Closing Date. Seller shall also indemnify and hold harmless
AMSC and its Affiliates  (including the Companies) from and against (iv) any and
all Other Tax Costs relating to any Taxes described in this Section 8.7(a),  and
(v) any and all Taxes and Other Tax Costs  arising in any  Taxable  Year  ending
after the Closing Date that result from any  adjustment  to any Tax Return of or
including the Company for any Taxable Year ending on or before the Closing Date,
provided,  however, that the indemnification  pursuant to this Section 8.7(a)(v)
shall not apply to the extent that such adjustment  relates to whether any asset
is depreciable or  amortizable,  and further  provided that any Tax or Other Tax
Cost  indemnifiable  under any other  provision  of this  Article 8 shall not be
indemnifiable a second time under this Section  8.7(a)(v),  and further provided
that any  indemnification  pursuant to this Section 8.7(a)(v) shall not apply to
any  adjustment  involving  any agreement  with a tax authority  unless it has a
Material   Adverse   Effect  on  any   Company  (or  any   successor   thereto).
Notwithstanding  the preceding,  Seller shall not be obligated to indemnify AMSC
or any of its Affiliates  (including  the  Companies)  for, in the case of taxes
described  in clauses  (ii),  (iii),  (iv) and (v),  any Taxes that  result from
AMSC's breach of any representation or warranty contained in this Article 8.

               (b)  AMSC  shall  indemnify  and  hold  harmless  Seller  and its
Affiliates from and against any and all Taxes with respect to which Seller,  any
of Seller's  Affiliates,  any Company or any entity as successor  thereto may be
liable to the  extent  such Taxes are (i)  attributable  to any breach of any of
AMSC's  representations or warranties  contained in this Article 8, (ii) insofar
as they relate to any Company or any entity as successor  thereto,  payable with
respect to any Taxable  Year  beginning  and ending after the Closing  Date,  or
(iii) insofar as they relate to any Company or any entity as successor  thereto,
payable  with  respect to that portion of any Split Period that begins after the
Closing  Date.  AMSC  shall  also  indemnify  and hold  harmless  Seller and its
Affiliates  from and  against  (iv) any and all Other Tax Costs  relating to any
Taxes  described in this Section  8.7(b).  Notwithstanding  the preceding,  AMSC
shall not be obligated to indemnify  Seller or any of its Affiliates for, in the
case of taxes  described in clauses (ii),  (iii) and (iv), any Taxes that result
from Seller's breach of any representation or warranty contained in this Article
8. For purposes of this Section  8.7(b),  if AMSC's  obligation to indemnify for
Taxes  arises as a result of the Merger  failing to qualify as a  reorganization
under Section 368(a) of the Code, such obligation  shall be limited to an amount
that reflects the value of the timing  difference  between (x) the year in which
such  Taxes  are  actually  payable  and (y) the year or  years in which  Seller
disposes of the AMSC Common Stock received by Seller in the merger,  adjusted to
take into account any Tax benefit Seller may realize from the early payment.

               (c) If the Seller's indemnification obligation under this section
8.7  arises  in  respect  of any  adjustment  (i) for  which  AMSC or any of its
Affiliates  (including any of the Companies) receives  indemnification  from the
Seller and (ii) which  results in any Tax  benefit to AMSC or any  Affiliate  of
AMSC  (including  any of the  Companies)  thereof for any Taxable  Year or Split
Period  beginning  after  the  Closing  Date  which  would  not,  but  for  such
adjustment,  be  available,  AMSC shall pay, or shall  cause to be paid,  to the
Seller an amount equal to the actual Tax saving  produced by such Tax benefit at
the time such Tax saving is realized by AMSC or any of its Affiliates (including
any of the Companies).  The amount of any such Tax saving for any Taxable period
shall be the amount of the reduction in Taxes  payable to a taxing  authority by
AMSC or any of its  Affiliates  (including  any of the  Companies)  thereof with
respect to such Taxable Year or Split Period as compared to the Taxes that would
have  been  payable  to a  taxing  authority  by AMSC  or any of its  Affiliates
(including  any of the  Companies)  with  respect to such  Taxable Year or Split
Period in the absence of such Tax benefit.

               (d) For  purposes of this  Section  8.7, in the case of any Taxes
that are  payable  with  respect to a Split  Period,  the  portion of such Taxes
allocable to Seller or to the portion of the Split Period  ending on the Closing
Date  shall be equal to (i) in the case of Taxes  imposed on the basis of income
or receipts,  an amount  determined on the basis of a closing of the books as of
the end of the Closing Date and (ii) in the case of any other Taxes, the product
of the total Taxes for the period  multiplied  by a fraction  the  numerator  of
which is the number of days in the Split  Period  from the  commencement  of the
Split Period through and including the Closing Date and the denominator of which
is the number of days in the entire Split Period  (provided,  however,  that for
purposes of this clause (ii)  appropriate  adjustments  shall be made to reflect
specific events that can be identified and  specifically  allocated as occurring
on or prior to the Closing Date (in which case Seller shall be  responsible  for
any Taxes  related  thereto) or occurring  after the Closing Date (in which case
AMSC shall be responsible for any Taxes related thereto)).  Notwithstanding  any
other provision in this Section 8.7(d), Section 8.2(a) or any other provision in
this Agreement,  any income,  gain, gross receipts,  net receipts or similar Tax
item  recognized  by any  Company as a result of any  transaction  described  in
Section 5.17 shall be treated as recognized by such Company for all Tax purposes
exclusively in (x) Taxable Years ending on or prior to the Closing Date,  and/or
(y) those  portions of Split Periods that are prior to and including the Closing
Date.

               (e)  Seller or AMSC,  as the case may be (the "Tax  Indemnitee"),
shall notify the other party (the "Tax  Indemnitor")  in writing in a reasonably
prompt  fashion  of any  written  inquiries,  notices  of audit,  assertions  of
liability,  or other written  communications  from or with a Tax authority  that
relate to Taxes with  respect to which the Tax  Indemnitor  may be liable  under
this Article 8 (a "Tax Claim").  Failure by the Tax Indemnitee to notify the Tax
Indemnitor  as  required  by  this  Sectio  8.7(e)  shall  not  relieve  the Tax
Indemnitor of its liability and obligation to indemnify the Tax Indemnitee under
this Agreement unless such failure  precludes the Tax Indemnitor from contesting
the Taxes giving rise to its indemnification  obligation and there is at least a
reasonable   possibility  that  the  Tax  Indemnitor  would  have  prevailed  in
challenging such Taxes.

               (f) Seller and AMSC shall take all  reasonable  steps and actions
necessary or  appropriate  to minimize any  indemnification  obligations  either
party may have under this Section 8.7.

               (g) Except as provided in the next  sentence,  within thirty (30)
days of receiving  notice of a Tax Claim,  the Tax Indemnitor,  at its sole cost
and expense, may elect, by written notice to the Tax Indemnitee,  to assume sole
responsibility for defending such Tax Claim, but only if, in such written notice
to the Tax  Indemnitee,  the  Tax  Indemnitor  acknowledges  full  and  complete
financial  responsibility  for all Taxes covered by such Tax Claim and all Other
Tax Costs  related  thereto.  Notwithstanding  the  provisions  of the preceding
sentence,  Seller shall not have the rights to settle or litigate any Tax Claim,
or to control and  determine  the timing and amount of any payment or deposit of
an amount relating to any Tax Claim, the submission or content of documentation,
returns or other Tax forms,  protests,  memoranda of law and briefs, the conduct
of  oral  arguments  or  presentations,  the  selection  of  witnesses  and  the
negotiation  of  stipulations  of fact with  respect to any Taxable  Year ending
after  the  Closing  Date.  If the Tax  Indemnitor  assumes  responsibility  for
defending a Tax Claim  pursuant to this  Section  8.7(g),  it shall keep the Tax
Indemnitee  reasonably  informed  of the status of such Tax  Claim,  and the Tax
Indemnitee and its  representatives  shall be entitled to attend any meetings or
hearings involving the Tax Claim at its own expense.  If the Tax Indemnitor does
not elect to assume  control of defending any Tax Claim,  the Tax Indemnitee may
settle  or defend  such Tax  Claim.  In such a case,  if the Tax  Indemnitor  is
responsible  for the  asserted  Taxes under this  Article 8, the Tax  Indemnitor
shall  indemnify the Tax Indemnitee for the reasonable  cost of its defense,  in
addition to the underlying Taxes.

               (h)  Any   unresolved   dispute   relating  to  any  payments  or
indemnification  obligations  of either Seller or AMSC to the other  pursuant to
the  provisions of this Article 8 shall be submitted to an  arbitrator  mutually
acceptable  to Seller and AMSC (or,  if the  parties are unable to agree upon an
arbitrator,  to an arbitrator selected by the American Arbitration Association).
Any such  arbitration  shall be  conducted in  accordance  with the rules of the
American Arbitration Association in effect at the time of the arbitration. Where
any dispute  relates to a position to be taken on any Tax Return of or including
a Company,  the  parties  shall use  reasonable  efforts to resolve  the dispute
informally or pursuant to  arbitration  prior to filing such Tax Return.  In the
event the  parties  are  unable to  resolve  any  dispute  prior to filing a Tax
Return,  the position  taken on the Tax Return shall have no impact or influence
on the  resolution  of the  underlying  dispute,  and in no way shall  prejudice
either  party's  rights  or  obligations  under  this  Article  8, nor shall any
resolution of any dispute have any impact on how a Tax Return must be filed.  In
the event an  indemnification  dispute arises that is based on a disagreement as
to  how  a  Tax  Return  of  or  including  a  Company  should  be  filed,   the
indemnification  obligations  of the  indemnifying  party under this Section 8.7
shall be determined  consistent with the filing position  advanced by such party
if such  position is not  inconsistent  with prior Tax  Returns  and  accounting
conventions and is proper and legal. If a Tax authority subsequently  determines
that  the  position  advanced  by  the  indemnifying  party  is  incorrect,  the
indemnifying party's obligation to indemnify the other party shall be determined
consistent with the determination of the Tax authority.

               (i) Notwithstanding Section 8.7(b), AMSC shall not be responsible
for,  and Seller  shall  indemnify  and hold  harmless  AMSC and its  Affiliates
(including the Companies)  from and against any and all Taxes or Other Tax Costs
with  respect to which any  Company or any entity as  successor  thereto  may be
liable to the extent such Taxes arise in any Taxable Year ending  after  Closing
Date that result from any income, net receipts,  gross receipts, gain or similar
items recognized by any Company as a result of the transactions  contemplated in
Section 5.16.

               (j) AMSC and Seller  agree to cooperate in good faith in carrying
out the provisions of this Article 8.

               (k) This  Article 8 shall be  construed  and applied to avoid any
double  counting of any payments,  credits or other benefits with respect to any
representation, warranty, covenant or indemnity set forth herein.

             Section 8.8  Exclusive Remedy for Taxes.   Except  as  provided  in
                          --------------------------
Section 7.3, this Article 8 provides the  exclusive  agreement  between  Seller,
AMSC and their respective  Affiliates regarding  responsibility for the Taxes of
the Companies.


             Section  8.9  Survival and Purchase Price Adjustment.
                           --------------------------------------

                    (a)  Notwithstanding  any other provision of this Agreement,
the covenants,  promises,  indemnifications and other obligations of the parties
hereto set forth in this Article 8 shall survive the Closing until fully carried
out and the expiration of any applicable statute of limitations  relating to the
Taxes covered thereby.

                    (b) In the event any payments are made to Seller pursuant to
the provisions of this Article 8, such payments are  adjustments to the purchase
price paid for the MAI Shares as set forth in Section 2.2(B).


                 ARTICLE 9. TERMINATION OF AGREEMENT; PAYMENT OF
                               EXPENSES; WAIVER OF CONDITIONS

               Section  9.1  Termination  Pre-Closing.  Anything  herein  to the
                             ------------------------
contrary  notwithstanding,  this  Agreement may be terminated at any time before
the Closing Date as follows  (such date of  termination  being the  "Termination
Date"), and in no other manner:


                    (a) Mutual  Consent.  By mutual written consent of Purchaser
                        ---------------
and Seller.

                    (b) Expiration Date. By either  Purchaser or Seller,  if the
                        ---------------
Closing shall not have occurred on or before June 30, 1998.

                    (c) Early Expiration Date. By Seller, if the Purchaser shall
                        ---------------------
have not  provided  to Seller a waiver or evidence  (satisfactory  to Seller) of
satisfaction  of the  condition  set forth in Section  6.1(l) on or prior to the
later of (i) 60 days after the end of the initial FCC comment period relating to
the  transactions   contemplated   hereby,  and  (ii)  14  days  after  the  FCC
Authorization,  for any reason  other than the breach or  inaction  of the party
seeking to exercise its termination rights under this Section 9.1.

                    (d)  Prohibition.  By  written  notice of  either  Seller or
                         -----------
Purchaser  if there shall have been entered a Final Order or  injunction  of any
Governmental   Entity   restraining  or  prohibiting  the  consummation  of  the
transactions  contemplated  hereby,  including but not limited to the failure of
the parties to obtain an FCC Authorization.
                        

                    (e) Breach;  Failure of  Condition.  Purchaser may terminate
                        ------------------------------
this  Agreement  by giving  written  notice  to Seller at any time  prior to the
Closing in the event Seller is (and AMSC and Purchaser are not) in breach in any
material  respect,  and Seller may terminate  this  Agreement by giving  written
notice to Purchaser  at any time prior to the Closing in the event  Purchaser or
AMSC  is  (and  Seller  is  not)  in  breach  in any  material  respect,  of any
representation, warranty, or covenant contained in this Agreement and, in either
case, such breach has not been fully cured by the breaching party within 30 days
after written notice of such breach has been delivered to the breaching party by
the terminating party;

                    (f) Share Price.  Seller may terminate this Agreement on the
                        -----------
Closing Date if the Market Value of a share of AMSC Common Stock  calculated  as
of the Closing  Date has  declined  by more than 30% from the Market  Value of a
share of AMSC Common Stock  calculated as of the date hereof,  after taking into
account all stock splits,  reverse stock splits and similar  adjustments  to the
number of shares of AMSC Common Stock outstanding on the date hereof.

                    (g) FCC Final Order.  Seller or Purchaser may terminate this
                        ---------------
Agreement in the event that a Final Order of the FCC has not been received when,
under the terms of the Escrow  Agreement,  any period of time  applicable to the
Escrowed Funds has expired  thereby  causing a return of the Escrowed  Funds, by
providing notice to such other party within 30 Business Days of such expiration.
In the event a termination occurs pursuant to this Section 9.1(g):


                         (i) Purchaser shall return the Shares to Seller;

                         (ii) Seller shall  return to Purchaser  the AMSC Common
Stock  issued to Seller  for the MAA  Shares  pursuant  to the terms of  Section
2.1(a); and

                         (iii) each of the parties  shall have only those rights
and obligations held by such party prior to the Closing Date.


               Section  9.2  Termination  Post-Closing.  In the  event  that the
                             -------------------------
Closing proceeds upon receipt of an FCC Authorization that is not a Final Order,
and an adverse Final Order of the FCC is received that will not permit Purchaser
to  operate  MAA,  MAI and  the  Subsidiaries  as  contemplated,  Purchaser  may
terminate this  Agreement by providing  notice to Seller within 30 Business Days
of  receipt  of the  adverse  Final  Order  of the  FCC.  In  the  event  that a
termination occurs pursuant to this Section 9.2:


                    (a) the Escrow Agent shall return the MAI Purchase  Price to
the Purchaser;

                    (b) Purchaser shall return the Shares to Seller;

                    (c) Seller shall  return to Purchaser  the AMSC Common Stock
issued to Seller for the MAA Shares pursuant to the terms of Section 2.1(a); and

                    (d)  each   parties   shall  have  only  those   rights  and
obligations held by such party prior to the Closing Date.


             Section 9.3 Payment of Expenses;  Waiver of Conditions.  (a) Except
                         ------------------------------------------
as set forth in  Section  9.3(b),  in the event  that  this  Agreement  shall be
terminated  pursuant to this Article 9, all  obligations  of the parties  hereto
under this  Agreement  shall  terminate  and there shall be no  liability of any
party to any other  party  hereto and each party  hereto  will pay all costs and
expenses  incident to its  negotiation  and preparation of this Agreement and to
its performance of and compliance  with all agreements and conditions  contained
herein  on its part to be  performed  or  complied  with,  including  the  fees,
expenses  and  disbursements  of its counsel,  its  auditors and its  actuaries;
provided,  however,  that if this  Agreement  shall be  terminated  pursuant  to
Section  9.1(b),  such  termination  shall not release any party hereto from any
liability  that  such  party  may have  for any  breach  occurring  prior to the
Termination Date of any representation,  warranty or covenant made by such party
in this Agreement.

                    (b) In the event this  Agreement is  terminated  pursuant to
Section 9.1(c),  then Seller shall be entitled to be reimbursed by Purchaser for
its expenses  incurred in connection  with the  negotiation and execution of and
otherwise in connection with this Agreement which expenses shall be deemed to be
equal to  $4,000,000  in  immediately  available  funds,  which  funds  shall be
delivered to Seller not later than two days after the Termination Date.


                            ARTICLE 10. MISCELLANEOUS

               Section  10.1   Amendments.   Subject  to  applicable  law,  this
                               ----------
Agreement and any exhibit or schedule attached hereto may be amended at any time
prior to the  Closing  Date by an  instrument  in writing  duly  signed by or on
behalf of each of the parties hereto.


             Section 10.2  Further Instruments and Assurances.   At  or prior to
                           ----------------------------------
and after the Closing, each party shall from time to time, at the request of any
other party and without further cost or expense to such other party, execute and
deliver  such  other  instruments  and  take  such  other  actions  as  shall be
reasonably  required by any other party in order to carry out the  transactions,
agreements and covenants contained in or contemplated by this Agreement.

             Section 10.3 Public Announcements.  Press releases and other public
                          --------------------
communications  of any  sort  relating  to this  Agreement  or the  transactions
contemplated hereby shall be subject to the prior written consent of all parties
to this Agreement as to the contents of any such public disclosure, such consent
not being unreasonably withheld, conditioned or delayed; provided, however, each
party  hereto  shall be entitled  to make any  disclosure  as is required  under
applicable law, subpoena or final,  nonappealable court order, in the reasonable
judgment of such disclosing party.

            Section 10.4  Governing  Law. THIS AGREEMENT AND THE LEGAL RELATIONS
                          --------------
BETWEEN THE PARTIES SHALL BE GOVERNED BY AND  CONSTRUED IN  ACCORDANCE  WITH THE
LAWS OF THE  STATE OF NEW  YORK,  WITHOUT  REFERENCE  TO THE  CONFLICTS  OF LAWS
PROVISIONS THEREOF.

             Section 10.5 Notices. All communications under this Agreement shall
                          -------  
be in  writing  and shall be  deemed to have been duly  given (i) on the date of
receipt  if  served  personally  or by  confirmed  facsimile  or  other  similar
communication,  (ii) on the first day after sending if sent for guaranteed  next
day delivery by a next-day  courier  service or (iii) on the fourth Business Day
after mailing if mailed to the party or parties to whom notice is to be given by
registered or certified mail,  return receipt  requested,  postage prepaid,  and
properly addressed as follows:

             If to Purchaser:

                      American Mobile Satellite Corporation
                      10802 Parkridge Boulevard
                      Reston, Virginia  20191-5416
                      Attention:  General Counsel
                      Facsimile:  (703) 758-6134

                      and

                      American Mobile Satellite Corporation
                      10802 Parkridge Boulevard
                      Reston, Virginia  20191-5416
                      Attention:  Chief Executive Officer
                      Facsimile:  (703) 758-6106


             With a copy to:

                      Arnold & Porter
                      555 12th Street, N.W.
                      Washington, D.C. 20004
                      Attention:  Samuel A. Flax, Esq.
                      Facsimile:  (202) 942-5999

             If to Seller:

                      Motorola, Inc.
                      1303 East Algonquin Road
                      Schaumburg, Illinois 60196
                      Attention:  General Counsel
                      Facsimile:  (847) 576-3628

             With a copy to:

                      Kirkland & Ellis
                      200 East Randolph Drive
                      Chicago, Illinois 60601
                      Attention:  Mark B. Tresnowski
                      Facsimile:  (312) 861-2200

Any party may change its address for purposes of this Section 10.5 by giving the
other parties hereto notice of the new address in the manner set forth above.

              Section 10.6  Assignment and Binding  Effect.  This  Agreement may
                            ------------------------------
not be assigned by any party  hereto  without the prior  written  consent of the
other parties. Subject to the foregoing, all of the terms and provisions of this
Agreement  shall be binding upon and inure to the benefit of and be  enforceable
by the successors and assigns of the parties hereto.


              Section 10.7  Entire Agreement.  This  Agreement, the exhibits and
                            ----------------
schedules hereto,  the Disclosure  Schedule dated as of even date herewith,  and
other documents  delivered  pursuant hereto,  referred to herein or executed and
delivered in connection with the transactions  contemplated hereby,  contain the
entire  agreement  among  Purchaser,  Seller,  MAA and MAI with  respect  to the
transactions  contemplated herein and, except as provided herein,  supersede all
previous negotiations, commitments and writings.

              Section 10.8  Severability.  Whenever  possible, each provision of
                            ------------
this  Agreement  will be interpreted in such manner as to be effective and valid
under  applicable  law,  but if any  provision  of this  Agreement is held to be
prohibited  by  or  invalid  under   applicable  law,  such  provision  will  be
ineffective  only to the  extent  of such  prohibition  or  invalidity,  without
invalidating the remainder of such provision or the remaining provisions of this
Agreement.


              Section 10.9  Counterparts.  This  Agreement  may  be executed and
                            ------------
delivered  in two or more  counterparts,  each  of  which  shall  be  deemed  an
original.
 

              Section 10.10  No  Third  Party  Beneficiaries.  Nothing  in  this
                             -------------------------------
Agreement  is  intended  to confer any rights or  remedies,  whether  express or
implied,  under or by reason of this  Agreement,  on any persons  other than the
parties hereto and their respective  successors and assigns,  nor is anything in
this  Agreement  intended to relieve or discharge the obligation or liability of
any third persons to any party to this Agreement. Notwithstanding the preceding,
any other provision  herein or in any Collateral  Agreement,  Purchaser and AMSC
shall be entitled to assign this Agreement, to third party lenders as collateral
for their loans from such entities.

             Section 10.11 Delays or Omissions. No delay or omission to exercise
                           -------------------
any right, power or remedy accruing to Purchaser, AMSC or Seller upon any breach
or default of Purchaser,  AMSC or Seller,  respectively,  under this  Agreement,
shall  impair  any such  right,  power or remedy  of such  party nor shall it be
construed  to be a waiver of any such  breach  or  default,  or an  acquiescence
therein, or in any similar breach or default thereafter occurring; nor shall any
waiver of any single breach or default be deemed a waiver of any other breach or
default theretofore or thereafter occurring.

             Section 10.12  Construction.  This  Agreement  is  to  be deemed to
                            ------------
have been prepared jointly by the parties hereto after arms length negotiations,
and any  uncertainty  or  ambiguity  existing  herein  shall not be  interpreted
against  any  party,   but  according  to  the   application  of  the  rules  of
interpretation of contracts.


             Section 10.13  Knowledge Standard.  The term "knowledge," "best  of
                            ------------------ 
knowledge," "know" and any similar term when used with respect to Seller, MAA or
MAI means actual (and not  constructive)  knowledge of any director,  officer or
employee of Seller or an Affiliate of Seller,  including but not limited to MAA,
MAI and the Subsidiaries.



             Section 10.14 Expenses.  Except as otherwise  provided herein,  all
                           --------
costs,  fees and expenses  incurred in connection  with this Agreement  shall be
paid by the party  incurring such cost, fee or expense,  except that filing fees
related to the FCC Consents shall be shared jointly by Seller and Purchaser. All
costs  and  expenses  of MAA,  MAI  and the  Subsidiaries  associated  with  the
negotiation,  execution,  delivery and  consummation  of the Agreement  shall be
deemed to be the  responsibility  of Seller and at or before the Closing Sellers
shall reimburse MAA, MAI and the Subsidiaries therefor.








<PAGE>





             IN WITNESS  WHEREOF,  each of Seller,  MAA, MAI, AMSC and Purchaser
has caused this  Agreement to be duly executed on its behalf,  as of the day and
year first above written.

                                           MOTOROLA, INC.


                                           By:/s/James G. Roseland
                                                 -----------------
                                              Name:  James G. Roseland
                                                     -----------------
                                              Title: Vice President
                                                     --------------


                                           MOTOROLA ARDIS ACQUISITION, INC.


                                           By:/s/James G. Roseland
                                                 -----------------
                                              Name:  James G. Roseland
                                                     -----------------
                                              Title: Vice President
                                                     --------------



                                           MOTOROLA ARDIS, INC.


                                           By:/s/Theodore W. Schaffner
                                                 ---------------------
                                              Name:  Theodore W. Schaffner
                                                     ---------------------
                                              Title:  Corporate Vice President 
                                                       and Director of Business 
                                                       Development
                                                      --------------------------


                                           AMERICAN MOBILE SATELLITE CORPORATION


                                           By:/s/Gary M. Parsons
                                                 ---------------
                                              Name:  Gary M. Parsons
                                                     ---------------
                                              Title:  CEO and President
                                                      -----------------








<PAGE>






                                           AMSC ACQUISITION COMPANY, INC.



                                           By:/s/Gary M. Parsons
                                                 ---------------
                                              Name:  Gary M. Parsons
                                                     ---------------
                                              Title:  CEO and President
                                                      -----------------


<PAGE>
                                   EXHIBIT A

THIS  SECURITY HAS NOT BEEN  REGISTERED  UNDER THE  SECURITIES  ACT OF 1933,  AS
AMENDED,  OR ANY STATE SECURITIES LAWS AND MAY NOT BE TRANSFERRED OR SOLD EXCEPT
IN COMPLIANCE THEREWITH OR PURSUANT TO AN EXEMPTION THEREFROM.


                               AMERICAN MOBILE SATELLITE CORPORATION


                               Warrant for the Purchase of Shares of
                       Common Stock of American Mobile Satellite Corporation

No. ___                                                      Warrant to Purchase
                                                            ____________  Shares

             FOR  VALUE  RECEIVED,  AMERICAN  MOBILE  SATELLITE  CORPORATION,  a
Delaware corporation (the "Company"),  hereby certifies that MOTOROLA, INC., its
successor  or  permitted  assigns (the  "Holder"),  is entitled,  subject to the
provisions of this Warrant, to purchase from the Company, at the times specified
herein,  _______________  (___________)  (the "Warrant Share Amount") fully paid
and  non-assessable  shares of Common Stock of the  Company,  par value $.01 per
share (the "Common Stock"),  at a purchase price per share equal to the Exercise
Price (as hereinafter defined).  The Warrant Share Amount and the Exercise Price
are subject to adjustment from time to time as hereinafter set forth.

                    1.  DEFINITIONS.  The following terms, as used herein,  have
the following meanings:

             "Accepted Alien Ownership  Percentage  Limitation" means 24.99% or,
in the event of a modification of the Alien Ownership Restrictions subsequent to
the date hereof,  such percentage  limitation upon the Company's Alien ownership
as may







<PAGE>


be in effect from time to time as a result of such modification, less 0.01%.

             "Alien" means any alien or a representative  thereof,  or a foreign
              -----
government  or a  representative  thereof,  or a  corporation  or  other  entity
organized under the laws of any foreign government.

             "Alien Ownership Percentage" means, with respect to any Person, the
              -------------------------- 
percentage  of total  ownership in such Person  owned of record,  as well as the
percentage of total ownership in such Person voted, by Aliens; provided, that if
under the Alien  Ownership  Restrictions  such Person  would be deemed to have a
percentage of total  ownership owned of record or voted by Aliens other than the
actual  percentage  so  owned or  voted,  then  such  Person's  Alien  Ownership
Percentage shall be such deemed percentage.

             "Alien  Ownership   Restrictions"   means  Section  310(b)  of  the
              ------------------------------- 
Communications  Act, as modified by any  interpretation,  ruling or order of the
Federal  Communications  Commission (or any successor agency)  applicable to the
Company or any of its subsidiaries.

             "AMSC" means AMSC Acquisition Company, Inc., a Delaware corporation
              ----
and a wholly-owned subsidiary of the Company.

             "Board of Directors" means the Board of Directors of the Company.
              ------------------

             "Business Day" means any day except a Saturday, Sunday or other day
              ------------
on which  commercial  banks in the  City of New  York are  authorized  by law to
close.

             "Closing Price" has the meaning set forth in Section 10.D.
              -------------

             "Common Stock" has the meaning set forth in the preamble hereof.
              ------------

             "Communications  Act"  means  the  Communications  Act  of 1934, as
              -------------------
amended, or any successor statute.

             "Company" has the meaning set forth in the preamble hereof.
              -------

             "Constituent Person" has the meaning set forth in Section 11.
              ------------------

             "Current Market Price Per  Common Share" has  the meaning set forth
              --------------------------------------
in Section 10.D.

             "Exercise  Date"  means the  applicable  date of  exercise  of this
              --------------
Warrant, as indicated on the Warrant Exercise Notice delivered by the Holder.

             "Exercise  Price"  means  initially  $0.01 per  Warrant  Share,  as
              ---------------
adjusted from time to time.

             "Exercising Holder" has the meaning set forth in Section 3.A.
              -----------------

             "Expiration Date" means ______ __, 200_, at 5:00 p.m. New York City
              ---------------
 time.

             "FCC"  means  the  Federal  Communications   Commission,   or  such
              ---
successor agency of the Federal government with responsibility for administering
the Communications Act.

             "MAA" means Motorola ARDIS Acquisition, Inc.
              ---

             "MAI" means Motorola ARDIS, Inc.
              ---

             "NASDAQ" means the  National Market  of the National Association of
              ------
Securities Dealers, Inc. Automated Quotation System.

             "NASD Limit" has the meaning set forth in Section 4.
              ----------

             "NYSE" means the New York Stock Exchange Inc.
              ----

             "Non-Electing Share" has the meaning set forth in Section 11.
              ------------------

             "Person" means an  individual,  corporation,  partnership,  limited
              ------
liability  company,  association,  trust or any  other  entity  or  organization
including a government or political  subdivision or an agency or instrumentality
thereof.

             "Registration  Rights  Agreement"  has  the  meaning  set  forth in
              -------------------------------    
Section 16.

             "Securities Act" means the Securities Act of 1933, as amended,  and
              --------------
the rules and regulations promulgated thereunder.

             "Stock Purchase  Agreement"  means the Stock Purchase  Agreement by
              -------------------------
and among the Company,  AMSC, the Holder, MAA and MAI, dated as of December ___,
1998.

             "Warrant Exercise Notice" means the Warrant Exercise Notice forming
              -----------------------
a part hereof.

             "Warrant  Margin"  means,  on any date,  the  difference of (x) the
              ---------------
greater of (A) the average of the Closing Prices (as defined in Section 10.D) on
each of the 20 trading days immediately  preceding such date and (B) the Closing
Price [on the  trading  days]  prior to the such  date,  minus (y) the  Exercise
Price.

             "Warrant Share  Amount"  has the  meaning set forth in the preamble
              ---------------------
hereof.

             "Warrant Shares" means the shares of Common Stock  deliverable upon
              --------------
exercise of this Warrant, as adjusted from time to time.

                    2. EXERCISE OF WARRANT.

                    A.  Subject to Section 15 hereof,  the Holder is entitled to
exercise  this Warrant in whole or in part at any time, or from time to time, to
and including the Expiration Date or, if such day is not a Business Day, then on
the next  succeeding day that shall be a Business Day. To exercise this Warrant,
the Holder shall  execute and deliver to the Company at its address set forth in
Section 12 hereof a Warrant  Exercise Notice  substantially  in the form annexed
hereto and shall deliver to the Company (x) this Warrant,  including the Warrant
Exercise  Subscription  Form forming a part hereof duly  executed by the Holder,
and (y) subject to Section 2.B, payment of the Exercise Price then in effect for
such Warrant Shares. Upon such delivery and payment,  the Holder shall be deemed
to be the  holder of record of the  Warrant  Shares  subject  to such  exercise,
notwithstanding  that the stock  transfer  books of the  Company  shall  then be
closed or that  certificates  representing such Warrant Shares shalL not then be
actually delivered to the Holder.

                    B. The Exercise Price may be paid in cash or by certified or
official bank check or bank cashier's  check payable to the order of the Company
or by wire transfer of immediately  available funds to an account  designated by
the  Company or by  cancellation  of  indebtedness  owed to the Holder or by any
combination  of such methods.  In the  alternative,  the Holder may exercise its
right to  receive  Warrant  Shares (i) on a net basis,  such that,  without  the
exchange of any funds,  the Holder will  receive  that number of Warrant  Shares
(and such other consideration)  otherwise issuable (or payable) upon exercise of
this Warrant  less that number of Warrant  Shares  having an  aggregate  Current
Market  Price Per  Common  Share on the  Exercise  Date  equal to the  aggregate
Exercise Price that would otherwise have been paid by the Holder for the Warrant
Shares or (ii) delivery to the Company,  together with appropriate stock powers,
of  certificates  evidencing  shares of Common Stock having an aggregate Current
Market  Price  Per  Common  Share  on the  Exercise  Date of not  less  than the
aggregate  Exercise Price. The Company shall pay any and all documentary,  stamp
or similar  issue or transfer  taxes payable in respect of the issue or delivery
of this Warrant and the issue and delivery of the Warrant Shares.

                    C. If the  Holder  exercises  this  Warrant  in  part,  this
Warrant shall be  surrendered  by the Holder to the Company and a new Warrant of
the same  tenor  and for the  unexercised  number  of  Warrant  Shares  shall be
executed by the Company.  The Company shall register the new Warrant in the name
of the Holder or in such name or names of its transferee(s)  pursuant to Section
8 hereof as may be directed in writing by the Holder and deliver the new Warrant
to the Person or Persons entitled to receive the same.

                    D. Except as otherwise provided in Section 3, upon surrender
of this Warrant in conformity with the foregoing  provisions,  the Company shall
transfer to the Holder of this Warrant appropriate  evidence of ownership of the
shares of Common Stock or other securities or property  (including any money) to
which the Holder is entitled,  registered or otherwise  placed in, or payable to
the order of,  the name or names of the  Holder or its  transferee(s)  as may be
directed in writing by the Holder,  and shall deliver such evidence of ownership
and any other  securities  or  property  (including  any money) to the Person or
Persons entitled to receive the same, together with an amount in cash in lieu of
any fraction of a share as provided in Section 7 below.

                    3. OWNERSHIP LIMITATION.  If at any time the exercise of any
Warrants  pursuant  to  Section 2 would  cause  the  Company's  Alien  Ownership
Percentage to exceed the Accepted Alien Ownership Percentage Limitation, then in
lieu of issuing shares of Common Stock pursuant to Section 2:

                    A.  the  Company  shall  issue  to  each  Holder  exercising
               Warrants at such time (each an  "Exercising  Holder") whose Alien
                                                ------------------
               Ownership  Percentage is less than or equal to the Accepted Alien
               Ownership  Percentage  Limitation  the number of shares of Common
               Stock to which such  Exercising  Holder is  entitled  pursuant to
               Section 2;

                    B. the Company shall issue to each  Exercising  Holder whose
               Alien  Ownership  Percentage  is greater than the Accepted  Alien
               Ownership  Percentage  Limitation (each, an "Affected  Exercising
               Holder") a number of shares of Common Stock equal to the quotient
               of (x) the  product of (A) the  number of shares of Common  Stock
               that,  immediately after giving effect to any issuances of Common
               Stock pursuant to the foregoing Section 3.A, could be issued to a
               Person with a 100% Alien Ownership Percentage without causing the
               Company's Alien Ownership Percentage to exceed the Accepted Alien
               Ownership Percentage Limitation,  multiplied by (B) the number of
               shares of Common Stock to which such Affected  Exercising  Holder
               would be entitled  pursuant to Section 2 but for the  application
               of  this  Section  3,  divided  by (y)  the  product  of (A)  the
               aggregate  number of shares of Common Stock to which all Affected
               Exercising  Holders  would be entitled  pursuant to Section 2 but
               for the  application  o this  Section 3,  multiplied  by (B) such
               Affected Exercising Holder's Alien Ownership Percentage; provided
               that in no event  shall the  number  of  shares  of Common  Stock
               issuable  to any  Affected  Exercising  Holder  pursuant  to this
               Section 3.B exceed the number of shares of Common  Stock to which
               such Affected Exercising Holder would have been entitled pursuant
               to Section 2 but for the application of this Section 3; and

                    C. the Company shall deliver by wire transfer of immediately
               available funds to the account of each Affected Exercising Holder
               specified in such Affected  Exercising  Holder's Warrant Exercise
               Notice,  an  amount  equal to the  product  of (x) the  number of
               shares of Common Stock to which such Affected  Exercising  Holder
               would  have  been  entitled  pursuant  to  Section 2 that are not
               issuable  to such  Affected  Exercising  Holder  pursuant  to the
               foregoing  Section 3.B,  multiplied by (y) the Warrant  Margin on
               the Exercise Date.

                    4. RESTRICTIVE LEGEND.  Upon original issuance thereof,  and
until such time at the same shall have been registered  under the Securities Act
or sold  pursuant to Rule 144  promulgated  thereunder  (or any similar  rule or
regulation),  each Warrant and any certificates  evidencing Warrant Shares shall
bear a legend  substantially  in the form of the  legend  set forth on the first
page hereof,  unless in the opinion of counsel  reasonably  satisfactory  to the
Company, such legend is no longer required by the Securities Act.

                    5. RESERVATION OF SHARES.  The Company hereby agrees that at
all times it shall  reserve for  issuance  and  delivery  upon  exercise of this
Warrant such number of its  authorized  but  unissued  shares of Common Stock as
will be  sufficient  to permit the  exercise in full of this  Warrant.  All such
shares shall be duly  authorized  and, when issued upon such exercise,  shall be
validly  issued,  fully  paid and  non-assessable,  free and clear of all liens,
security  interests,  charges and other  encumbrances  or  restrictions  on sale
(other than general regulatory  restrictions  under the Communications  Act) and
free and clear of all preemptive rights.

                    6.  FRACTIONAL   SHARES.   No  fractional  shares  or  scrip
representing fractional shares shall be issued upon the exercise of this Warrant
and in lieu of delivery of any such fractional  share upon any exercise  hereof,
the  Company  shall pay to the Holder an amount in cash  equal to such  fraction
multiplied by the Current Market Price Per Common Share on the Exercise Date.

                    7. EXCHANGE, TRANSFER OR ASSIGNMENT OF WARRANT.

                    A. The Company shall from time to time register the exchange
               or transfer of any outstanding  Warrant in a Warrant  register to
               be maintained by the Company upon surrender  thereof  accompanied
               by a  written  instrument  or  instruments  of  transfer  in form
               satisfactory  to the  Company,  duly  executed by the  registered
               Holder  or  Holders  thereof  or  by  the  duly  appointed  legal
               representative  thereof or by a duly  authorized  attorney.  Each
               taker and holder of this  Warrant by taking or holding  the same,
               consents  and agrees  that the  registered  holder  hereof may be
               treated by the Company and all other  Persons  dealing  with this
               Warrant as the  absolute  owner hereof for any purpose and as the
               Person entitled to exercise the rights represented hereby.

                    B. Prior to any  proposed  transfer  of the  Warrants or the
               Warrant  Shares,  unless  such  transfer  is made  pursuant to an
               effective  registration  statement  under the  Securities Act the
               Holder  will  deliver  to the  Company,  if so  requested  by the
               Company,  an opinion of counsel  reasonably  satisfactory in form
               and substance to the Company,  to the effect that the Warrants or
               Warrant  Shares,   as  applicable,   may  be  sold  or  otherwise
               transferred  without   registration  under  the  Securities  Act.
               Subject to the  preceding  sentence,  the Holder of this  Warrant
               shall be entitled,  without obtaining the consent of the Company,
               to assign and transfer this Warrant, at any time in whole or from
               time to time in part,  to any Person or  Persons.  Subject to the
               foregoing,  upon  surrender  of  this  Warrant  to  the  Company,
               together with the attached Warrant Assignment Form duly executed,
               the  Company  shall,  without  charge,  execute and deliver a new
               Warrant in the name of the  assignee or  assignees  named in such
               instrument of assignment  and, if the Holder's entire interest is
               not being assigned,  in the name of the Holder,  and this Warrant
               shall promptly be cancelled.

                    8. LOSS OR  DESTRUCTION  OF  WARRANT.  Upon  receipt  by the
Company  of  evidence  satisfactory  to it (in the  exercise  of its  reasonable
discretion) of the loss, theft,  destruction or mutilation of this Warrant,  and
(if  requested  by the  Company in the case of loss,  theft or  destruction)  of
reasonably satisfactory indemnification,  and upon surrender and cancellation of
this Warrant, if mutilated,  the Company shall execute and deliver a new Warrant
of like tenor and date  representing the right to purchase an equivalent  number
of Warrant Shares.

                    9. ANTI-DILUTION PROVISIONS.

                    A. In case the  Company  shall at any  time  after  the date
               hereof (i)  declare a dividend or make a  distribution  on Common
               Stock  payable in Common Stock or other  shares of the  Company's
               capital   stock,   (ii)   subdivide,   split  or  reclassify  the
               outstanding  Common Stock into a larger  number of shares,  (iii)
               combine or reclassify the outstanding Common Stock into a smaller
               number of shares,  or (iv) issue any shares of its capital  stock
               in  a  reclassification  of  Common  Stock  (including  any  such
               reclassification  in connection with a consolidation or merger in
               which the Company is the  continuing  corporation),  then in each
               such case the Warrant Share Amount shall be adjusted to equal the
               number of shares to which the holder of this  Warrant  would have
               been entitled  upon the  occurrence of such event if this Warrant
               had  been  exercised   immediately   prior  to  such  time.  Such
               adjustment shall be made  successively  whenever any event listed
               above shall occur.

                    B. In case  the  Company  shall  fix a  record  date for the
               making of a  distribution  to holders of Common Stock  (including
               any such  distribution made in connection with a consolidation or
               merger in which the  Company is the  continuing  corporation)  of
               evidences of  indebtedness,  assets or other property  (excluding
               cash dividends, other cash distributions from current or retained
               earnings  or  dividends  payable  in  Common  Stock  for which an
               adjustment  has been made pursuant to Section  9.A),  the Warrant
               Share  Amount to be in effect  after  such  record  date shall be
               determined  by  multiplying  the Warrant  Share  Amount in effect
               immediately  prior  to  such  record  date  by  a  fraction,  the
               numerator  of which shall be the Current  Market Price Per Common
               Share,  and the denominator of which shall be such Current Market
               Price Per Common Share on such record date,  less the fair market
               value  (determined  by the  Board of  Directors  of the  Company;
               provided   that  if  the   Holder   shall   object  to  any  such
               determination, the Board of Directors shall retain an independent
               appraiser reasonably satisfactory to the Holder to determine such
               fair market value) of the portion of the assets,  other  property
               or  evidence  of  indebtedness  so to  be  distributed  which  is
               applicable to one share of Common Stock.  Such adjustments  shall
               be made successively whenever such a record date is fixed; and in
               the event  that such  distribution  is not so made,  the  Warrant
               Share  Amount  shall again be  adjusted  to be the Warrant  Share
               Amount  which would then be in effect if such record date had not
               been fixed.

                    C. If as a result of any event or for any other reason,  any
               adjustment is made which increases the number of shares of Common
               Stock  issuable upon  conversion,  exercise or exchange of, or in
               the conversion or exercise price or exchange ratio applicable to,
               any  outstanding  securities of the Company that are  convertible
               into, or exercisable  or  exchangeable  for,  Common Stock of the
               Company, then a corresponding  adjustment shall be made hereunder
               to increase the Warrant Share Amount, but only to the extent that
               no such  adjustment  has been made  pursuant  to Section 9.A or B
               hereof with respect to such event or for such other reason.

                    D. For the  purpose of any  computation  under  Section 3 or
               Section 9.B hereof, on any determination date the "Current Market
                                                                  --------------
               Price  Per  Common  Share"  shall  be  deemed  to be the  average
               -------------------------
               (weighted  by daily  trading  volume) of the  Closing  Prices (as
               defined  below) per share of Common Stock for the 20  consecutive
               trading  days  immediately  prior to such date.  "Closing  Price"
               means (1) if shares of Common Stock then are listed and traded on
               the    NYSE,    the    closing    price    on    such    day   as
               reported, on the NYSE Composite  Transactions Tape; (2) if shares
               of Common  Stock then are not listed and traded on the NYSE,  the
               closing price on such day as reported by the  principal  national
               securities  exchange  on which the shares are listed and  traded;
               (3) if shares of Common  Stock  then are not listed and traded on
               any such  securities  exchange,  the last  reported sale price on
               such day on the NASDAQ; or (4) if shares of Common Stock then are
               not  traded on the NASDAQ  National  Market,  the  average of the
               highest  reported bid and lowest reported asked price on such day
               as reported  by NASDAQ.  If on any  determination  date shares of
               Common Stock are not quoted by any such organization, the Current
               Market  Price Per Common  Share shall be the fair market value of
               such shares on such determination  date as reasonably  determined
               by the Board of  Directors.  If the  Holder  shall  object to any
               determination  by the Board of  Directors  of the Current  Market
               Price Per Common Share, the Current Market Price Per Common Share
               shall be the fair  market  value  per  share of  Common  Stock as
               determined by an independent appraiser retained by the Company at
               its expense and reasonably acceptable to the Holder. For purposes
               of any computation  under this Section 9, the number of shares of
               Common  Stock  outstanding  at any given time  shall not  include
               shares owned or held by or for the account of the Company.

                    E. No adjustment in the Warrant Share Amount or the Exercise
               Price shall be required unless such  adjustment  would require an
               increase  or  decrease  of at least one  percent of such  amount;
               provided that any adjustments which by reason of this Section 9.F
               are not  required  to be made shall be carried  forward and taken
               into account in any subsequent adjustment. All calculations under
               this  Section 9 shall be made to the  nearest one tenth of a cent
               or to the nearest  hundredth of a share as the case may be.

                    G.  In the  event  that,  at any  time  as a  result  of the
               provisions  of this  Section 9, the holder of this  Warrant  upon
               subsequent  exercise shall become  entitled to receive any shares
               of capital  stock of the  Company  other than Common  Stock,  the
               number of such other shares so  receivable  upon exercise of this
               Warrant shall  thereafter  be subject to adjustment  from time to
               time in a manner and on terms as nearly equivalent as practicable
               to the provisions contained herein.

                    H.  Upon any  adjustment  pursuant  to this  Section  9, the
               Company shall promptly  thereafter (i) cause to be filed with the
               Company a certificate of an officer of the Company  setting forth
               the Warrant Share Amount and Exercise Price after such adjustment
               and setting forth in reasonable  detail the method of calculation
               and the facts upon which such  calculations  are based,  and (ii)
               cause to be given to each  registered  Holder of this  Warrant at
               the  address as set forth in  Section  11 written  notice of such
               adjustments.  Where  appropriate,  such  notice  may be  given in
               advance  and  included  as a part of the  notice  required  to be
               delivered pursuant to Section 12.B.

                    10.  REORGANIZATION,   CONSOLIDATION,  MERGER,  OR  SALE  OF
ASSETS.  In  case  of any  reclassification,  redesignation,  reorganization  of
recapitalization  by the  Company  (other  than as set  forth in  Section  9) or
consolidation  of the Company  with,  or merger of the Company  into,  any other
Person, any merger of another Person into the Company (other than a merger which
does not result in any reclassification, conversion, exchange or cancellation of
outstanding shares of Common Stock) or any sale or transfer of all substantially
all of the assets of the Company or of the Person  formed by such  consolidation
or resulting from such merger or which acquires such assets, as the case may be,
the Holder shall have the right thereafter to exercise this Warrant for the kind
and  amount  of  securities,  cash  and  other  property  receivable  upon  such
reclassification,      redesignation,     reorganization,      recapitalization,
consolidation,  merger,  sale or transfer by a holder of the number of shares of
Common Stock for which this Warrant may have been exercised in full  immediately
prior to such reclassification, redesignation, reorganization, recapitalization,
consolidation,  merger,  sale or  transfer,  assuming  (i) such holder of Common
Stock is not a Person  with  which the  Company  consolidated  or into which the
Company  merged  or which  merged  into the  Company  or to which  such  sale or
transfer was made, as the case may be ("Constituent Person"), or an Affiliate of
a Constituent  Person and (ii) in the case of a consolidation,  merger,  sale or
transfer  which includes an election as to the  consideration  to be received by
the  holders,  such  holder of Common  Stock  failed to  exercise  its rights of
election,  as to the kind or  amount  of  securities,  cash and  other  property
receivable upon such  consolidation,  merger, sale or transfer (provided that if
the kind or amount of securities,  cash and other property  receivable upon such
consolidation, merger, sale or transfer is not the same for each share of Common
Stock held immediately prior to such consolidation,  merger, sale or transfer by
other than a Constituent  Person or an Affiliate thereof and in respect of which
such rights of election  shall not have been exercised  ("Non-electing  share"),
then for the purpose of this Section 10 the kind and amount of securities,  cash
and other property receivable upon such consolidation,  merger, sale or transfer
by each  Non-electing  share  shall  be  deemed  to be the kind  and  amount  so
receivable per share by a plurality of the Non-electing shares.  Adjustments for
events subsequent to the effective date of such reclassification, redesignation,
reorganization, recapitalization, consolidation, merger and sale of assets shall
be as nearly equivalent as may be practicable to the adjustments provided for in
this  Warrant.  In any such  event,  effective  provisions  shall be made in the
certificate  or  articles  of   incorporation  of  the  resulting  or  surviving
corporation,  in any  contract  of  sale,  conveyance,  lease  or  transfer,  or
otherwise  so that the  provision  set forth  herein for the  protection  of the
rights of the Holder shall  thereafter  continue to be applicable;  and any such
resulting or surviving  corporation  shall  expressly  assume the  obligation to
deliver,  upon  exercise,  such  shares of  stock,  other  securities,  cash and
property.  The provisions of this Section 11 shall similarly apply to successive
consolidations, mergers, sales, leases or transfers.

                    11. NOTICES.  Any notice,  demand or delivery  authorized or
required by this Warrant shall be in writing and shall be given to the Holder or
the Company, as the case may be, at its address (or telecopier number) set forth
below, or such other address (or telecopier number) as shall have been furnished
to the party giving or making such notice, demand or delivery:

             If to the Company:

                      American Mobile Satellite Corporation
                      10802 Parkridge Blvd.
                      Reston, VA  22091
                      Telecopy:  (703) 758-6134
                      Attention:    Randy Segal,
                                    General Counsel

             With a copy to:

                      Arnold & Porter
                      555 - 12th Street, N.W.
                      Washington, D.C.  20004
                      Telecopy: (202) 942-5999
                      Attention:    Samuel A. Flax, Esq.

             If to the Holder:

                      Motorola, Inc.
                      Law Department, IL01/11
                      1303 E. Algonquin Road
                      Schaumburg, IL  60196
                      Telecopy: (847) 576-3628
                      Attention:    Linda Valentine,
                                    Corporate Vice President and General Counsel

             With a copy to:

                      Kirkland & Ellis
                      200 E. Randolph Avenue
                      Chicago, IL  60601
                      Telecopy: (312) 861-2200
                      Attention:    Mark Tresnowski, Esq.

Each  such  notice,  demand  or  delivery  shall  be  effective  (i) if given by
telecopy,  when such telecopy is  transmitted to the telecopy  number  specified
herein and the intended  recipient confirms the receipt of such telecopy or (ii)
if given by any other means, when received at the address specified herein.

                    12. NOTICES TO WARRANT HOLDERS.

                    A. The Company shall  provide to the Holder,  at its address
               and in the manner set forth in Section 12, a notice of expiration
               of this  Warrant not less than 90 nor more than 120 days prior to
               the Expiration Date.

                    B. In the event:

                         (a) the Company shall authorize the issuance to holders
                    of shares of Common Stock of rights,  options or warrants to
                    subscribe  for or purchase  shares of Common Stock or of any
                    other subscription rights or warrants; or

                         (b) the Company  shall  authorize the  distribution  to
                    holders of shares of Common Stock of assets, including cash,
                    evidences of its indebtedness, or other securities; or

                         (c) of any  reorganization,  consolidation or merger to
                    which the  Company is a party and for which  approval of any
                    shareholders   of  the  Company  is  required,   or  of  the
                    conveyance or transfer of the  properties  and assets of the
                    Company   substantially   as  an   entirety,   or   of   any
                    reclassification  or change of Common  Stock  issuable  upon
                    exercise  of the  Warrants,  or a tender  offer or  exchange
                    offer for shares of Common Stock; or

                         (d)  of  the  voluntary  or  involuntary   dissolution,
                    liquidation or winding up of the Company; or




                                      - 2 -



                         (e) the Company  proposes to take any action that would
                    require an  adjustment  to the Warrant  Share  Amount or the
                    Exercise Price pursuant to Section 10 hereof;

then the  Company  shall  cause to be given  to the  registered  Holder  of this
Warrant,  at  least 20 days  prior to the  applicable  record  date  hereinafter
specified,  or 20 days  prior to the date of the event in the case of events for
which there is no record date a written  notice stating (i) the date as of which
the  holders of record of shares of Common  Stock  entitled  to receive any such
rights,  options,  warrants or  distribution  are to be determined,  or (ii) the
initial  expiration  date set forth in any tender  offer or  exchange  offer for
shares of  Common  Stock,  or (iii)  the date on which any such  reorganization,
reclassification,  consolidation,  merger,  conveyance,  transfer,  dissolution,
liquidation or winding up is expected to become  effective or  consummated,  and
the date as of which it is expected  that  holders of record of shares of Common
Stock  shall be  entitled  to  exchange  such  shares  for  securities  or other
property,  if  any,  deliverable  upon  such  reorganization,  reclassification,
consolidation, merger, conveyance, transfer, dissolution, liquidation or winding
up. The failure to give the notice  required by this  Section 13.B or any defect
therein  shall not affect the legality or validity of any  distribution,  right,
option,  warrant,  consolidation,  merger,  conveyance,  transfer,  dissolution,
liquidation or winding up, or the vote upon any action.

                         13. RIGHTS OF THE HOLDER.  Prior to the exercise of any
Warrant,  the Holder shall not, by virtue hereof, be entitled to any rights of a
stockholder of the Company, including, without limitation, the right to vote, to
receive dividends or other distributions, to exercise any preemptive right or to
receive any notice of meetings of  stockholders or any notice of any proceedings
of the  Company  except as may be  specifically  provided  for  herein.  Nothing
contained  herein  shall  impose any  obligation  on the Holder to purchase  any
securities  or impose any  liabilities  on such Holder as a  stockholder  of the
Company,  whether such  obligation or liabilities are asserted by the Company or
by creditors of the Company.

                         14. LIMITATION ON EXERCISE OF WARRANT;  CANCELLATION OF
WARRANTS. Notwithstanding anything to the contrary in this Warrant, this Warrant
shall be  exercisable  at any given time only for the  number of Warrant  Shares
which is equal to the applicable  Warrant Share Amount as in effect from time to
time.

                         15. REGISTRATION  RIGHTS. The Holder of this Warrant is
entitled  to certain  registration  rights with  respect to the  Warrant  Shares
issuable upon the exercise thereof.  Said registration rights are set forth in a
Registration  Rights  Agreement  dated as of December __, 1997, by and among the
Company and the Holder (the "Registration  Rights Agreement").  By acceptance of
this Warrant,  the Holder  hereof agrees that upon exercise of this Warrant,  in
whole or in part, such Holder will be bound by the Registration Rights Agreement
as a holder of Registrable Securities  thereunder.  The Company agrees that upon
transfer of this Warrant, in whole or in part, pursuant to Section 7 hereof, the
transferee  shall be  entitled  to  become a party  to the  Registration  Rights
Agreement  if not already a party  thereto.  A copy of the  Registration  Rights
Agreement  may be obtained  by the Holder  hereof  upon  written  request to the
Company.

                         16.  GOVERNING  LAW  AND  WAIVER  OF JURY  TRIAL.  THIS
WARRANT AND ALL RIGHTS  ARISING  HEREUNDER  SHALL BE CONSTRUED AND DETERMINED IN
ACCORDANCE  WITH THE INTERNAL LAWS OF THE STATE OF NEW YORK, AND THE PERFORMANCE
THEREOF SHALL BE GOVERNED AND ENFORCED IN ACCORDANCE WITH SUCH LAWS. THE PARTIES
HERETO IRREVOCABLY WAIVE ANY RIGHT TO A JURY TRIAL WITH RESPECT TO ANY ACTION OR
PROCEEDING ARISING OUT OF OR RELATING TO THIS AGREEMENT.

                         17. AMENDMENTS;  WAIVERS. Any provision of this Warrant
may be amended or waived if, and only if, such amendment or waiver is in writing
and signed,  in the case of an amendment,  by the Holder and the Company,  or in
the case of a waiver,  by the party  against whom the waiver is to be effective.
No failure or delay by either party in exercising any right,  power or privilege
hereunder  operate as a waiver  thereof or shall any single or partial  exercise
thereof  preclude any other or further  exercise  thereof or the exercise of any
other right,  power of privilege.  The rights and remedies herein provided shall
be cumulative and not exclusive of any rights or remedies provided by law.

                         18.  COUNTERPARTS.  This Warrant may be executed in any
number of counterparts,  each of which shall be deemed to be an original and all
of which together shall constitute one and the same instrument.

                         19. FCC COMPLIANCE.  Notwithstanding  any provisions of
this  Warrant to the  contrary,  in the event that the consent of the FCC to the
exercise of this Warrant is required to be obtained prior to such exercise, this
Warrant  shall not be  exercisable  unless and until such FCC consent shall have
been  obtained.  In the event that this Warrant is intended to be exercised  and
such FCC consent is required to be  obtained,  the Company and the Holder  shall
use commercially reasonable efforts to obtain such FCC consent promptly.

                            (signature page follows)







<PAGE>





                                      - 3 -




             IN WITNESS WHEREOF,  the Company has duly caused this Warrant to be
signed by its duly authorized officer and to be dated as of ________ __, 1998.

                                         AMERICAN MOBILE SATELLITE
                                          CORPORATION



                                         By:____________________________
                                         Name:
                                         Title:

Acknowledged and Agreed:

MOTOROLA, INC.



By:__________________________
Name:
Title:






<PAGE>





                                      - 4 -



                                      WARRANT EXERCISE NOTICE

                         (To be delivered prior to exercise of the Warrant
                      by execution of the Warrant Exercise Subscription Form)


To:          American Mobile Satellite Corporation
             10802 Parkridge Blvd.
             Reston, VA  22091

               The undersigned  hereby notifies you of its intention to exercise
the Warrant to purchase  shares of Common  Stock,  par value $.01 per share,  of
American Mobile Satellite  Corporation.  The undersigned intends to exercise the
Warrant to purchase ______________ shares (the "Shares") at $0.01 per Share (the
"Exercise  Price")  [pursuant to the [net  exercise]  [delivery of Common Stock]
 ---------------
provision of Section 2.B of the Warrant].  [The  undersigned  intends to pay the
aggregate  Exercise  Price for the Share in cash,  certified or official bank or
bank cashier's  check or by wire transfer of immediately  available  funds to an
account to designated by the Company or by cancellation of indebtedness  owed to
the Holder (or a combination of such methods) as indicated below.]

             The undersigned  hereby certifies that to the best of its knowledge
its Alien Ownership Percentage as of the date hereof is ___________.

Date: ________________________

                                         -----------------------------
                                         (Signature of Owner)

                                         ------------------------------
                                         (Street Address)

                                         ------------------------------
                                         (City)    (State)   (Zip Code)

Payment:    $_____________ cash
            $_____________ check
            $_____________ wire transfer
            $_____________ cancellation of indebtedness

[Wire  Transfer  Instructions,  if  required  pursuant  to Section 3 or 4 of the
Warrant: _______________________]





                                


<PAGE>





                                      - 5 -



                       WARRANT EXERCISE SUBSCRIPTION FORM

                (To be executed only upon exercise of the Warrant
                   after delivery of Warrant Exercise Notice)


To:          American Mobile Satellite Corporation
             10802 Parkridge Blvd.
             Reston, VA  22091

             The undersigned  irrevocably exercises the Warrant for the purchase
of _______________________ shares (the "Shares") of Common Stock, par value $.01
per share, of American Mobile Satellite Corporation (the "Company") at $____ per
Share (the "Exercise Price") and [herewith makes payment of $____________,  such
payment  being made in cash or by certified or official  bank or bank  cashier's
check payable to the order of the Company or by wire transfer or by cancellation
of  indebtedness  owed to the Holder or any  combination  of such  methods] [the
undersigned  Holder is  exercising  the Warrant  pursuant to the [net  exercise]
[delivery of shares of Common  Stock]  provision of Section 2.B of the Warrant],
all on the  terms and  conditions  specified  in the  Warrant,  surrenders  this
Warrant  and all right,  title and  interest  therein to the Company and directs
that the Shares  deliverable  upon the exercise of this Warrant be registered or
placed in the name and at the address specified below and delivered thereto.  If
said  number of Shares is less than all of the shares of Common  Stock for which
the  Warrant  is  exercisable,  the  undersigned  requests  that  a new  Warrant
representing  the remaining  balance of such shares be registered in the name of
the  undersigned  or  nominee  hereinafter  set  forth,  and  further  that such
certificate be delivered to the undersigned at the address hereinafter set forth
or to such other person or entity as is hereinafter set forth.

Date:__________________________


                                         -----------------------------
                                         (Signature of Owner)

                                         ------------------------------
                                         (Street Address)

                                         ------------------------------
                                         (City)    (State)   (Zip Code)




                                


<PAGE>





                                      - 6 -



Securities and/or check to be issued to:

Please insert social security or identifying
number:_______________________________________________

Name:  _______________________________________________

Street Address:  _____________________________________

City, State and Zip Code:  ___________________________


Any unexercised  portion of the Warrant  evidenced by the [within] Warrant to be
issued to:

Please insert social security or identifying 
number:_______________________________________________


Name:  _______________________________________________

Street Address:  _____________________________________

City, State and Zip Code:  ___________________________








<PAGE>





                                      - 7 -


                             WARRANT ASSIGNMENT FORM

                                                              Dated:____________


          FOR  VALUE  RECEIVED,   _____________________________   hereby  sells,
assigns and transfers unto  ____________________________________________________
(the "Assignee") (please type or print in block letters),

                           (insert Assignee's address)

            --------------------------------------------------------
           (insert Assignee's social security and taxpayer ID number)

its right to  purchase  up to ____ shares of Common  Stock  represented  by this
Warrant  and  does  hereby  irrevocably   constitute  and  appoint  ____________
Attorney,  to transfer the same on the books of the Company,  with full power of
substitution in the premises.



                                                  ----------------------------
                                                  Signature


Signature Guarantee:









<PAGE>


                                  Exhibit 10.66

                         Participation Rights Agreement

                  THIS PARTICIPATION RIGHTS AGREEMENT (this "Agreement") is made
as of December 31, 1997,  by and among  Motorola,  Inc., a Delaware  corporation
(the "Investor"),  American Mobile Satellite Corporation, a Delaware corporation
(the  "Company"),  and the  parties  listed on  Schedule A attached  hereto (the
"Stockholders").

                  American Mobile Satellite Corporation, a Delaware corporation,
the Investor and certain others are parties to a Stock Purchase  Agreement dated
as of  December  31,  1997 (the  "Purchase  Agreement").  In order to induce the
Investor to enter into the Purchase  Agreement,  the Stockholders have agreed to
the provisions set forth in this Agreement.  Unless  otherwise  provided in this
Agreement,  capitalized  terms used herein  shall have the meanings set forth in
Section 5 hereof.

                  The parties hereto agree as follows:

                  1.  Investor  Participation  Rights.  At any  time  after  the
Closing Date and prior to the date on which the Investor  beneficially owns less
than 5% of the Common Stock on a fully-diluted basis:

                  (a) At least 30 days prior to any transfer,  assignment or any
other disposition of Stockholder Shares (other than a transfer (i) to the public
pursuant  to Rule 144  under the  Securities  Act (or any  similar  rule then in
force) or (ii) in other  sales  through a broker or dealer in the  public  stock
market  over  an  exchange  or the  Nasdaq  Stock  Market  (a  "Transfer"),  the
transferring  Stockholder  (the  "Transferring  Stockholder")  shall  deliver  a
written  notice (the "Sale  Notice") to the  Investor,  specifying in reasonable
detail the identity of the prospective transferee(s),  the number of Stockholder
Shares to be transferred and the terms and conditions of the Transfer (including
the proposed price at which the Stockholder  Shares is to be  transferred).  The
Investor may elect to  participate  in the  contemplated  Transfer by delivering
written notice of such election to the Transferring  Stockholder  within 30 days
after delivery of the Sale Notice. If the Investor elects to participate in such
Transfer,  each of the  Transferring  Stockholder  and  the  Investor  shall  be
entitled to sell in the contemplated Transfer, at the same price and on the same
terms, a number of  Stockholder  Shares equal to the product of (A) the quotient
determined by dividing the number of Stockholder  Shares owned by such Person by
the aggregate number of Stockholder Shares owned by the Transferring Stockholder
and the  Investor  and (B) the  number of  Stockholder  Shares to be sold in the
contemplated Transfer.

          For  example  (by  way  of  illustration  only),  if the  Sale  Notice
          contemplated a sale of 100 shares of Common Stock by the  Transferring
          Stockholder,  and if the  Transferring  Stockholder  at such time owns
          shares which  constitute 30% of all Common Stock which are Stockholder
          Shares and if the Investor  elects to participate in such Transfer and
          the Investor owns shares of Common Stock which  constitutes 10% of all
          of the Common Stock which are  Stockholder  Shares,  the  Transferring
          Stockholder would be entitled to sell 75 shares of Common Stock (30% /
          40% x 100 shares) and the Investor would be entitled to sell 25 shares
          of Common Stock (10% / 40% x 100 shares).


<PAGE>




                  (b) The Transferring  Stockholder will use its best efforts to
obtain the agreement of the prospective  transferee(s)  to the  participation of
the Investor in any contemplated Transfer, and the Transferring Stockholder will
not  Transfer any of its  Stockholder  Shares to the  prospective  transferee(s)
unless (i)  simultaneously  with such Transfer,  the  prospective  transferee(s)
purchases from the Investor at the same price and on the same terms,  the number
of  Stockholder  Shares  which  it is  entitled  to  sell  to  such  prospective
transferee  pursuant  to  Section  1 above  or  (ii)  simultaneously  with  such
Transfer,  the  Transferring  Stockholder  purchases  the number of  Stockholder
Shares  from the  Investor  at the same  price and on the same  terms  which the
Investor would have been entitled to sell pursuant to Section 1 above.

                  2.  Shareholder  Participation  Rights.  At any time after the
Closing Date and prior to the date on which the Investor  beneficially owns less
than 5% of the Common Stock on a fully-diluted basis:

                  (a) At least 30 days prior to any transfer,  assignment or any
other  disposition of Stockholder  Shares by the Investor (other than a transfer
(i) to the public  pursuant to Rule 144 under the Securities Act (or any similar
rule  then in force)  or (ii) in other  sales  through a broker or dealer in the
public stock market over an exchange or the Nasdaq Stock Market) (a "Transfer"),
the  Investor  shall  deliver  a  written  notice  (the  "Sale  Notice")  to the
Stockholders,  specifying in reasonable  detail the identity of the  prospective
transferee(s),  the number of Stockholder Shares to be transferred and the terms
and  conditions  of the  Transfer  (including  the  proposed  price at which the
Stockholder  Shares is to be transferred).  The Stockholders may elect, pro rata
based on the number of  Stockholder  Shares owned by them, to participate in the
contemplated  Transfer  by  delivering  written  notice of such  election to the
Investor  within 30 days after delivery of the Sale Notice.  If any  Stockholder
elects to  participate  in such  Transfer,  the Investor and each such  electing
Stockholder  (an  "Electing  Stockholder")  shall  be  entitled  to  sell in the
contemplated  Transfer,  at the same  price and on the same  terms,  a number of
Stockholder  Shares  equal to the  product  of (A) the  quotient  determined  by
dividing the number of Stockholder  Shares owned by such Person by the aggregate
number of Stockholder Shares owned by the Electing Stockholders and the Investor
and  (B) the  number  of  Stockholder  Shares  to be  sold  in the  contemplated
Transfer.

         For  example  (by  way  of  illustration  only),  if  the  Sale  Notice
         contemplated a sale of 100 shares of Common Stock by the Investor,  and
         if the  Investor at such time owns shares which  constitute  30% of all
         Common Stock which are Stockholder Shares and if Electing  Stockholders
         elect to participate in such Transfer and the Electing Stockholders own
         shares of Common Stock which constitutes 10% of all of the Common Stock
         which are Stockholder Shares, the Investor would be entitled to sell 75
         shares  of  Common  Stock  (30% / 40% x 100  shares)  and the  Electing
         Stockholders would be entitled to sell 25 shares of Common Stock (10% /
         40% x 100 shares).



                                      - 2 -

<PAGE>



                  (b) The  Investor  will use its best  efforts  to  obtain  the
agreement of the prospective  transferee(s) to the participation of the Electing
Stockholders in any  contemplated  Transfer,  and the Investor will not Transfer
any of its  Stockholder  Shares  to the  prospective  transferee(s)  unless  (i)
simultaneously with such Transfer, the prospective  transferee(s) purchases from
the Electing Stockholders at the same price and on the same terms, the number of
Stockholder  Shares  which  they  are  entitled  to  sell  to  such  prospective
transferee  pursuant  to  Section  2 above  or  (ii)  simultaneously  with  such
Transfer,  the Investor will purchase the number of Stockholder  Shares from the
Electing Stockholders at the same price and on the same terms which the Electing
Stockholders would have been entitled to sell pursuant to Section 2 above.

                  3. Agreement to Vote for Transaction.  Each Stockholder agrees
that it shall vote all of its Stockholder Shares in favor of and take such other
action as may be  necessary  to  approve,  and hereby  consents  to the  Company
entering into, all of the transactions  contemplated by the Purchase  Agreement,
including the issuance of shares of Common Stock to the Investor.

                  4.  Registration  Rights  Agreement.  Pursuant to the Purchase
Agreement,  the Company  shall  provide the Investor  with certain  registration
rights  under a  registration  rights  agreement  substantially  in the  form of
Schedule  B  attached  hereto  (the  "Registration   Rights  Agreement").   Each
Stockholder  agrees and acknowledges  that pursuant to the  Registration  Rights
Agreement,  the Company shall provide the Investor with Demand Registrations and
Piggyback  Registrations (each as defined in the Registration Rights Agreement),
for  which  the  Investor  shall  have a  priority  of sale  of its  Registrable
Securities  (as defined in the  Registration  Rights  Agreement)  over all other
unregistered  securities  held by any other  stockholder  of the  Company.  Each
Stockholder  agrees to subordinate any registration  rights granted with respect
to the  unregistered  securities  of the  Company  owned  by it  (including  any
unregistered securities it may acquire in the future), to the Investor under the
Registration  Rights  Agreement,  and agrees  that it shall be bound by Sections
1(b) and 2(c)  therein  until the end of the 42nd month after the month in which
the Closing under the Purchase Agreement occurs (the "Subordination  Termination
Date").  After  the  Subordination   Termination  Date,  the  Investor  and  the
Stockholders  will be pari passu with  respect  to the  priority  of sale in any
piggyback  registration  rights  granted  to such  parties  as set  forth in the
Registration Rights Agreement.

                  5.       Definitions.

                  (a)      "Common Stock" means the Common Stock, par value $.01
                            ------------
per share, of the Company.

                  (b) "Stockholder  Shares" means (i) any shares of Common Stock
                       -------------------  
issued to the Stockholders and the Investor  (including shares issuable upon the
exercise of any AMSC Warrants) and (ii) any equity securities issued or issuable
directly or  indirectly  with respect to the Common Stock  referred to in clause
(i) above  (including  by way of stock  dividend or stock split or in connection
with a combination of shares,  recapitalization,  merger, consolidation or other
reorganization).  As to any particular shares  constituting  Stockholder Shares,
such  shares  will  cease to be  Stockholder  Shares  when  they  have  been (x)
effectively  registered  under the  Securities Act and disposed of in accordance
with the registration statement covering them, or (y) sold to the public through
a broker,  dealer or market maker pursuant to Rule 144 (or by similar  provision
then in force) under the Securities Act.


                                      - 3 -

<PAGE>



                  (c) Unless otherwise stated, other capitalized terms contained
herein have the meanings set forth in the Purchase Agreement.

                  6.       Miscellaneous.

                  (a)  Entire  Agreement;  No  Inconsistent   Agreements.   This
Agreement  contains the entire agreement between the parties hereto with respect
to the transactions contemplated herein and supersede all previous negotiations,
commitments  and  writings.  The  Company  shall not  hereafter  enter  into any
agreement with respect to its securities which is inconsistent  with or violates
the rights granted to the Investor in this Agreement.

                  (b) Remedies.  Any Person having rights under any provision of
this Agreement shall be entitled to enforce such rights  specifically to recover
damages caused by reason of any breach of any provision of this Agreement and to
exercise  all  other  rights  granted  by law.  The  parties  hereto  agree  and
acknowledge  that money damages may not be an adequate  remedy for any breach of
the provisions of this  Agreement and that any party may in its sole  discretion
apply to any court of law or equity of competent  jurisdiction  (without posting
any bond or other security) for specific  performance  and for other  injunctive
relief in order to  enforce  or  prevent  violation  of the  provisions  of this
Agreement.

                  (c)  Amendments  and  Waivers.  Except as  otherwise  provided
herein,  the provisions of this Agreement may be amended or waived only upon the
prior written consent of the Investor and the Stockholders.

                  (d)  Successors  and Assigns.  All covenants and agreements in
this Agreement by or on behalf of any of the parties hereto shall bind and inure
to the benefit of the  respective  successors  and assigns of the parties hereto
whether so expressed or not. In addition,  whether or not any express assignment
has been made,  the  provisions of this  Agreement  which are for the benefit of
purchasers  or holders  of the  Investor's  Stockholder  Shares are also for the
benefit of, and enforceable by, any subsequent holder of such shares.

                  (e) Severability.  Whenever  possible,  each provision of this
Agreement shall be interpreted in such manner as to be effective and valid under
applicable  law, but if any  provision of this  Agreement is held to be invalid,
illegal or  unenforceable in any respect under any applicable law or rule in any
jurisdiction,  such invalidity,  illegality or unenforceability shall not affect
any other  provision or the  effectiveness  or validity of any  provision in any
other jurisdiction, and this Agreement shall be reformed, construed and enforced
in such jurisdiction as if such invalid,  illegal or unenforceable provision had
never been contained herein.

                  (f)    Counterparts.    This   Agreement   may   be   executed
simultaneously  in two or more  counterparts  (including  by means of telecopied
signature pages),  any one of which need not contain the signatures of more than
one party, but all such counterparts taken together shall constitute one and the
same Agreement.

                  (g) Descriptive  Headings.  The  descriptive  headings of this
Agreement are inserted for convenience only and do not constitute a part of this
Agreement.



                                      - 4 -

<PAGE>



                  (h)  Governing  Law.  THIS  AGREEMENT  AND  THE  EXHIBITS  AND
SCHEDULES  HERETO SHALL BE GOVERNED BY, AND  CONSTRUED IN ACCORDANCE  WITH,  THE
LAWS OF THE STATE OF NEW YORK,  WITHOUT  GIVING  EFFECT TO ANY  CHOICE OF LAW OR
CONFLICT  OF LAW RULES OR  PROVISIONS  (WHETHER  OF THE STATE OF NEW YORK OR ANY
OTHER  JURISDICTION)  THAT  WOULD  CAUSE  THE  APPLICATION  OF THE  LAWS  OF ANY
JURISDICTION OTHER THAN THE STATE OF NEW YORK.

                  (i) Notices.  All notices,  demands or other communications to
be given or delivered  under or by reason of the  provisions  of this  Agreement
shall be in writing  and shall be deemed to have been  given when (i)  delivered
personally to the recipient,  (ii) sent to the recipient by reputable  overnight
courier service (charges prepaid),  (iii) sent by facsimile  transmission,  when
transmitted  and  receipt  is  confirmed  or (iv)  mailed  to the  recipient  by
certified or registered mail, return receipt requested and postage prepaid. Such
notices,  demands and other  communications shall be sent to the Stockholders at
their  respective  addresses  listed on  Schedule A  attached  hereto and to the
Investor at the address indicated below:

                  To the Investor:

                  Motorola, Inc.
                  1303 East Algonquin Road
                  Schaumburg, Illinois 60196
                  Attn: General Counsel
                  Facsimile: (847) 576-3628

                  With a copy (which will not constitute notice) to:

                  Kirkland & Ellis
                  200 East Randolph Drive
                  Chicago, Illinois 60601
                  Attn:  Mark B. Tresnowski, Esq.
                  Facsimile:  (312) 861-2200

                  To the Company:

                  American Mobile Satellite Corporation
                  10802 Parkridge Boulevard
                  Reston, Virginia 20191-5416
                  Attn:  General Counsel
                  Facsimile: (703) 758-6134



                                      - 5 -

<PAGE>



                  With a copy (which will not constitute notice) to:

                  Arnold & Porter
                  555 12th Street, N.W.
                  Washington, D.C. 20004
                  Attn:  Samuel A. Flax, Esq.
                  Facsimile:  (202) 942-5999

or to such  other  address  or to the  attention  of such  other  person  as the
recipient party has specified by prior written notice to the sending party.


                                    * * * * *


                                      - 6 -

<PAGE>



                  IN  WITNESS  WHEREOF,  the  parties  have duly  executed  this
Participation Rights Agreement as of the date first written above.


MOTOROLA, INC.,                       SATELLITE MOBILE TELEPHONE
a Delaware corporation                COMPANY, L.P.

By:/s/Julie A. Welch                  By:/s/Douglas I. Brandon

Name:  Julie A. Welch                 Name:  Douglas I. Brandon

Its:   Senior Operations Controller   Its:  VP - External Affairs & Law

HUGHES COMMUNICATIONS                 TRANSIT COMMUNICATIONS, INC.
 SATELLITE SERVICES, INC.

By:/s/Amnon Carr                      By:/s/Douglas I. Brandon

Name: Amnon Carr                      Name:  Douglas I. Brandon

Its: Assistant Treasurer,             Its:  VP - External Affairs & Law
     Hughes Electronics

SATELLITE COMMUNICATIONS              SINGAPORE
INVESTMENTS CORPORATION               TELECOMMUNICATIONS LTD.

By:/s/Douglas I. Brandon              By:/s/Yap Chee Keong

Name: Douglas I. Brandon              Name:  Yap Chee Keong

Its: VP - External Affairs & Law      Its:  Group Financial Controller

SPACE TECHNOLOGIES                    AMERICAN MOBILE SATELLITE
INVESTMENTS, INC.                     CORPORATION

By:/s/Douglas I. Brandon              By:/s/Gary M. Parsons

Name: Douglas I. Brandon              Name:  Gary M. Parsons

Its: VP - External Affairs & Law      Its:  Chief Executive Officer and 
                                             President


                                      - 7 -

<PAGE>




                         [Continuation of Signature Page
                       to Participation Rights Agreement]

Solely with respect to its Warrants:

BARON CAPITAL PARTNERS, L.P.
  By:    Baron Capital Management, Inc.,
         a General Partnership

By:/s/Morty Schaja
      ------------
Name:  Morty Schaja
       ------------
Its:  S.V.P.
      ------

For purposes of Sections 3 of the Participation Rights Agreement only:

BARON CAPITAL MANAGEMENT,
INC.

By:/s/Morty Schaja
      ------------
Name:  Morty Schaja
       ------------
Its:  S.V.P.
      ------

BAMCO, INC.

By:/s/Morty Schaja
      ------------
Name:  Morty Schaja
       ------------
Its:  S.V.P.
      ------



<PAGE>




                                   Schedule A


Hughes Communications Satellite Services, Inc.
1500 Hughes Way
Long Beach, California  90810

Space Technologies Investments, Inc.
1150 Connecticut Avenue, N.W.
4th Floor
Washington, D.C.  20036

Satellite Communications Investments Corporation
1150 Connecticut Avenue, N.W.
4th Floor
Washington, D.C.  20036

Satellite Mobile Telephone Company, L.P.
1150 Connecticut Avenue, N.W.
4th Floor
Washington, D.C.  20036

Transit Communications, Inc.
1150 Connecticut Avenue, N.W.
4th Floor
Washington, D.C.  20036

Singapore Telecommunications Ltd.
31C Exeter Road
#03-00 Comcentre III
Singapore 239734
Republic of Singapore

Baron Capital Management, Inc.
767 Fifth Avenue
24th Floor
New York, New York  10153

BAMCO, Inc.
767 Fifth Avenue
24th Floor
New York, New York  10153


<PAGE>



                                  EXHIBIT 11.1

                      AMERICAN MOBILE SATELLITE CORPORATION
                    COMPUTATIONS OF EARNINGS PER COMMON SHARE
                    (in thousands, except per share amounts)

<TABLE>
<CAPTION>


                                                                     Year Ended December 31,
                                                                     -----------------------
<S>                                                      <C>                <C>             <C>      
                                                            1997               1996           1995
                                                            ----               ----           ----
BASIC EARNINGS PER SHARE CALCULATION
- ------------------------------------

Net Loss                                                 ($119,207)         ($134,638)      ($66,917)
                                                         ==========         ==========      =========

Net Loss per common share                                   ($4.74)            ($5.38)        ($2.69)
                                                            =======            =======        =======

Weighted-average common shares outstanding                  25,131             25,041         24,900
                                                            =======            ======         ======


DILUTED EARNINGS PER SHARE CALCULATION
- --------------------------------------

Net Loss  (1)                                            ($119,207)         ($129,244)      ($66,917)
                                                         ==========         ==========      =========

Net Loss per common share                                   ($4.73)            ($5.13)        ($2.65)
                                                            =======            =======        =======

Weighted-average common shares outstanding (2)              25,197             25,179         25,278
                                                            ======             ======         ======


(1)  Calculated as follows:                                 1997               1996           1995
                                                            ----               ----           ----

Primary net loss                                         ($119,207)         ($134,638)      ($66,917)
Amortization of debt discount                                   --              2,253             --
Interest on convertible debt                                    --              3,141             --
                                                         ----------         ----------      ---------
                                                         ($119,207)         ($129,244)      ($66,917)
                                                         ==========         ==========      =========

(2) Calculated as follows:
      Historical weighted average number of shares          25,131             25,041         24,900
      Assumed exercise of stock options                          2                 63             92
      Assumed exercise of stock purchase                        64                 75            286
                                                         ----------           --------      --------
warrants
                                                            25,197             25,179         25,278
                                                            ======             ======        =======

</TABLE>



<PAGE>







                                                                EXHIBIT 21.1



              SUBSIDIARIES OF AMERICAN MOBILE SATELLITE CORPORATION


Name                                             Location of Incorporation


American Mobile Radio Corporation                State of Delaware

AMRC Holdings, Inc.                              State of Delaware

AMSC Acquisition Company, Inc.                   State of Delaware

AMSC Sales Corporation, Ltd.                     Territory of the Virgin Islands

American Mobile Satellite Sales Corporation      State of Delaware

AMSC Subsidiary Corporation                      State of Delaware and 
                                                 Commonwealth of Virginia

Personal Communications Satellite Corporation    State of Delaware

AMSC ARDIS Acquisition, Inc.                     State of Delaware

AMSC ARDIS, Inc.                                 State of Delaware

Radio Data Network Holding Corporation           State of New York

ARDIS Company                                    New York General Partnership

ARDIS Holding Company                            New York Limited Partnership












                                                                 Exhibit 23.1
                                                                 ------------

CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


As independent  public  accountants,  we hereby consent to the  incorporation by
reference of our reports  dated March 31, 1998,  included in this Form 10-K into
American Mobile Satellite Corporation's previously filed Registration Statements
on Form S-8 File Nos. 33-72852, 33-34250, 33-91714 and 333-30099.


March 31, 1998                               /s/Arthur Andersen LLP


<TABLE> <S> <C>


<ARTICLE>                     5
<LEGEND>
     This schedule  contains summary  financial  information  extracted from the
     Company's unaudited  Consolidated  Statement of Loss,  Consolidated Balance
     Sheet, and Consolidated  Statement of Cash Flows, in each case for the year
     ended  December 31, 1997,  and is qualified in its entirety by reference to
     such financial statements.
</LEGEND>
<MULTIPLIER>                                   1,000
<CURRENCY>                                     U.S. Dollars
       
<S>                             <C>
<PERIOD-TYPE>                   12-MOS
<FISCAL-YEAR-END>                              DEC-31-1997
<PERIOD-START>                                 JAN-01-1997
<PERIOD-END>                                   DEC-31-1997
<EXCHANGE-RATE>                                1
<CASH>                                         2,106 
<SECURITIES>                                   0
<RECEIVABLES>                                  4,564
<ALLOWANCES>                                   1,930
<INVENTORY>                                    40,321
<CURRENT-ASSETS>                               64,739
<PP&E>                                         233,174
<DEPRECIATION>                                 104,916
<TOTAL-ASSETS>                                 311,447
<CURRENT-LIABILITIES>                          59,433 
<BONDS>                                        218,563
                          0
                                    0
<COMMON>                                       252
<OTHER-SE>                                     46,131
<TOTAL-LIABILITY-AND-EQUITY>                   311,447
<SALES>                                        23,530
<TOTAL-REVENUES>                               44,214
<CGS>                                          40,335
<TOTAL-COSTS>                                  99,179
<OTHER-EXPENSES>                               42,430
<LOSS-PROVISION>                               0
<INTEREST-EXPENSE>                             21,633
<INCOME-PRETAX>                                (119,207)
<INCOME-TAX>                                   0
<INCOME-CONTINUING>                            (119,207)
<DISCONTINUED>                                 0
<EXTRAORDINARY>                                0
<CHANGES>                                      0
<NET-INCOME>                                   (119,207)
<EPS-PRIMARY>                                  (4.74)
<EPS-DILUTED>                                  (4.73)
        


</TABLE>


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