ALLEGIANCE TELECOM INC
424B4, 1999-04-20
TELEPHONE COMMUNICATIONS (NO RADIOTELEPHONE)
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<PAGE>   1
 
                                                Filed Pursuant to Rule 424(B)(4)
                                                      Registration No. 333-74763
PROSPECTUS
 
                               14,676,000 SHARES
                        [ALLEGIANCE TELECOM, INC., LOGO]
 
                                  COMMON STOCK
                               ------------------
 
     Allegiance Telecom, Inc. is selling 11,826,000 shares of its common stock
and certain selling stockholders are selling 2,850,000 shares of common stock
for a total of 14,676,000 shares of common stock. Allegiance will not receive
any part of the proceeds from the sale of shares by the selling stockholders.
The underwriters named in this prospectus may purchase up to 2,201,400
additional shares of common stock from Allegiance under certain circumstances.
 
     The common stock is quoted on the Nasdaq National Market under the symbol
"ALGX." The last reported sale price of the common stock on the Nasdaq National
Market on April 14, 1999, was $39.875 per share.
                               ------------------
 
      INVESTING IN THE COMMON STOCK INVOLVES CERTAIN RISKS. SEE "RISK FACTORS"
BEGINNING ON PAGE 7.
 
     Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.
                               ------------------
 
<TABLE>
<CAPTION>
                                                                  PER SHARE         TOTAL
                                                                  ---------      ------------
<S>                                                               <C>            <C>
Public Offering Price.......................................       $38.00        $557,688,000
Underwriting Discount.......................................       $ 1.52        $ 22,307,520
Proceeds to Allegiance (before expenses)....................       $36.48        $431,412,480
Proceeds to Selling Stockholders (before expenses)..........       $36.48        $103,968,000
</TABLE>
 
     The underwriters are offering the shares subject to various conditions. The
underwriters expect to deliver the shares to purchasers on or about April 20,
1999.
                               ------------------
 
                           JOINT BOOKRUNNING MANAGERS
 
SALOMON SMITH BARNEY                                        GOLDMAN, SACHS & CO.
                               ------------------
 
DONALDSON, LUFKIN & JENRETTE
 
                        MORGAN STANLEY DEAN WITTER
 
                                               WARBURG DILLON READ LLC
 
April 14, 1999
<PAGE>   2
 
                                     [Map]
<PAGE>   3
 
     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS.
ALLEGIANCE HAS NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH DIFFERENT INFORMATION.
ALLEGIANCE IS NOT MAKING AN OFFER OF THESE SECURITIES IN ANY STATE WHERE THE
OFFER IS NOT PERMITTED. YOU SHOULD NOT ASSUME THAT THE INFORMATION PROVIDED BY
THIS PROSPECTUS IS ACCURATE AS OF ANY DATE OTHER THAN THE DATE ON THE FRONT OF
THIS PROSPECTUS.
 
                             ---------------------
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                           <C>
Prospectus Summary..........................................    1
Risk Factors................................................    7
Use of Proceeds.............................................   16
Dividend Policy.............................................   16
Market Price of Common Stock................................   16
Dilution....................................................   17
Capitalization..............................................   18
Selected Financial Data.....................................   19
Management's Discussion and Analysis of Financial Condition
  and Results of Operations.................................   21
Business....................................................   33
Management..................................................   53
Certain Relationships and Related Transactions..............   62
Principal and Selling Stockholders..........................   64
Description of Certain Indebtedness.........................   66
Description of Capital Stock................................   69
Shares Eligible for Future Sale.............................   72
Underwriting................................................   73
Legal Matters...............................................   75
Experts.....................................................   75
Where You Can Find More Information.........................   76
Index to Consolidated Financial Statements..................  F-1
</TABLE>
 
                                        i
<PAGE>   4
 
                               PROSPECTUS SUMMARY
 
     This summary highlights information contained elsewhere in this prospectus.
This summary may not contain all of the information that you should consider
before purchasing our common stock. You should read the entire prospectus
carefully.
 
                                   ALLEGIANCE
 
     Allegiance seeks to be a premier provider of telecommunications services to
business, government and other institutional users in major metropolitan areas
across the United States. We offer an integrated set of telecommunications
products and services including local exchange, local access, domestic and
international long distance, enhanced voice, data and a full suite of Internet
services.
 
     Our business plan covers 24 of the largest metropolitan areas in the U.S.
We estimate that these 24 markets include more than 21 million non-residential
access lines, representing about 44.7% of the total non-residential access lines
in the U.S. With a strategy focusing on the central business districts and
suburban commercial districts in these areas, we plan to address a majority of
the non-residential access lines in most of our targeted markets. As of April
14, 1999, we were operating in thirteen markets: New York City, Dallas, Atlanta,
Fort Worth, Chicago, Los Angeles, San Francisco, Boston, Oakland, Philadelphia,
Washington, D.C., San Jose and Houston. As of that date we were in the process
of deploying our networks in four other markets: Long Island, Northern New
Jersey, Orange County and San Diego.
 
     Under the Telecommunications Act of 1996, we have the status of a
competitive local exchange carrier or "CLEC" and, as such, in each of our
markets we compete primarily with the existing or incumbent local exchange
carrier or "ILEC." The ILECs, such as Bell Atlantic, BellSouth and Southwestern
Bell, have historically had a monopoly in providing local wireline phone
service.
 
     Our principal executive offices are located at 1950 Stemmons Freeway, Suite
3026, Dallas, Texas 75207 and our telephone number is (214) 261-7100.
 
BUSINESS STRATEGY
 
     Our goal is to achieve significant market penetration and deliver superior
customer care while maximizing operating margins. The key components of our
strategy include the following:
 
          Leverage Proven Management Team. Our Chairman and Chief Executive
     Officer, Royce J. Holland, has more than 25 years of experience in the
     telecommunications and energy industries, including as President, Chief
     Operating Officer and co-founder of MFS Communications, one of the first
     companies to compete with the ILECs. Under his leadership, MFS
     Communications grew from a start-up operation to become the largest
     competitor to the incumbent local exchange carriers.
 
          Target Customers with Integrated Service Offerings. We focus
     principally on customers in the business, government and other
     institutional market segments. The majority of our customers are small and
     medium-sized businesses, to which we offer "one-stop shopping" by giving
     them the ability to purchase a comprehensive package of communications
     services from a single supplier.
 
          Utilize "Smart Build" Strategy to Maximize Speed to Market and
     Minimize Investment Risk. We will continue to pursue what we refer to as a
     "smart build" strategy. Under this strategy, we purchase and install
     switches, locate our equipment in the central office facilities of
     incumbent local exchange carriers and lease other elements of their
     networks until growth justifies our ownership of additional network assets.
     By this strategy, we intend to reduce our initial capital expenditures,
     reduce the time it takes to enter and expand in a geographic market and
     generate higher returns on invested capital.
 
          Achieve Broad Coverage of Attractive Areas within Each Targeted
     Market. We intend to address the most attractive service areas throughout
     each of our targeted markets, such as suburban business
 
                                        1
<PAGE>   5
 
     parks and concentrated downtown areas, without having to construct our own
     fiber network to the customer premises in each of these areas.
 
          Maximize Operating Margins by Emphasizing Facilities-Based
     Services. We believe that by using our own facilities to provide service,
     we should generate significantly higher gross margins than we could obtain
     by reselling services provided entirely on another carrier's facilities. As
     a result, we focus our marketing activities on areas where we can serve
     customers through a direct connection to our facilities.
 
          Build Market Share by Focusing on Direct Sales. We use a direct sales
     force to sell directly to customers and provide them personalized customer
     care through a single point of contact. By using this approach, we hope to
     maximize our market share, particularly among small and medium-sized
     businesses.
 
          Develop Efficient Automated Back Office Systems. We intend to automate
     most of the processes involved in switching a customer to our networks. Our
     goal is to minimize the time between customer order and service
     installation. To achieve this goal, we are developing, acquiring and
     integrating information technology systems to support our operations, and
     we are establishing an on-line and real-time connection of our operations
     support systems with those of the incumbent local exchange carriers, also
     referred to as "electronic bonding."
 
          Expand Through Potential Acquisitions. We plan to pursue strategic
     acquisitions to expand our customer base and acquire additional experienced
     management.
 
RECENT DEVELOPMENTS
 
     On April 1, 1999, we entered into a credit agreement and related guaranty
agreement with Goldman Sachs Credit Partners L.P., TD Securities (USA) Inc.,
Morgan Stanley Senior Funding, Inc. and various other lenders that provides for
a $225 million senior secured revolving credit facility maturing December 31,
2005 for a subsidiary of Allegiance Telecom, Inc. Our ability to borrow under
this facility is subject to various conditions. See "Description of Certain
Indebtedness -- Revolving Credit Facility." With the closing of this offering
and of the credit facility, we plan to accelerate deployment of our networks in
Detroit and Baltimore into 1999.
 
     Based on preliminary information, we estimate that for the three months
ended March 31, 1999, we had consolidated revenues of approximately $10 million,
selling, general and administrative expenses of approximately $28 million, net
loss applicable to common stock of approximately $49 million and earnings before
interest, income taxes, depreciation and amortization, management ownership
allocation charge and noncash deferred compensation of approximately negative
$25 million; and have made capital expenditures of approximately $61 million. We
believe that for the first quarter of 1999, we sold approximately 50,000 lines
and installed approximately 33,000 lines.
 
                                        2
<PAGE>   6
 
                                  THE OFFERING
 
Common stock offered by
Allegiance..........................     11,826,000 shares
 
Common stock offered by selling
stockholders........................      2,850,000 shares
 
          Total.....................     14,676,000 shares
 
Common stock to be outstanding after
the offering........................     62,215,115 shares
 
Use of proceeds.....................     We intend to use the net proceeds from
                                         this offering and our previous
                                         financing activities primarily to fund
                                         the costs of deploying networks in all
                                         24 of our targeted markets.
 
                                         We will not receive any proceeds from
                                         the sale of the shares by the selling
                                         stockholders.
 
Dividend policy.....................     We do not anticipate paying any cash
                                         dividends in the foreseeable future.
                                         Any future determination to pay
                                         dividends will be at the discretion of
                                         our board of directors and will be
                                         dependent upon then existing
                                         conditions, including our financial
                                         condition, results of operations,
                                         contractual restrictions, capital
                                         requirements, business prospects, and
                                         other factors our board of directors
                                         deems relevant.
 
Nasdaq National Market symbol.......     "ALGX"
 
     Unless we specifically state otherwise, the information in this prospectus
does not take into account the issuance of up to 2,201,400 shares of common
stock which the underwriters have the option to purchase solely to cover
over-allotments. If the underwriters exercise their over-allotment option in
full, 64,416,515 shares of common stock will be outstanding after the offering.
 
     The number of shares of common stock to be outstanding immediately after
the offering does not take into account 649,248 shares reserved for issuance
upon the exercise of outstanding warrants and 7,187,608 shares reserved under
our 1997 Stock Option Plan and 1998 Stock Incentive Plan and 2,238,489 shares
reserved under our Employee Stock Discount Purchase Plan. See
"Management -- Stock Plans" and "Description of Capital Stock."
 
                                  RISK FACTORS
 
     See "Risk Factors" for a discussion of certain factors relating to our
business and an investment in the common stock.
 
                                        3
<PAGE>   7
 
                             SUMMARY FINANCIAL DATA
 
     The summary consolidated financial data presented below as of and for the
year ended December 31, 1998 was derived from the audited consolidated financial
statements of Allegiance and the notes thereto contained elsewhere in this
prospectus, which statements have been audited by Arthur Andersen LLP,
independent public accountants. The summary pro forma statements of operations
data set forth below is unaudited and gives effect to:
 
     - Allegiance's initial public offering of common stock, including the
       conversion of the redeemable convertible preferred stock and the
       adjustments to reflect the equity allocation as described in footnote
       (1),
 
     - the sale of our 12 7/8% notes, 11 3/4% notes and redeemable warrants, and
 
     - the issuance of 11,826,000 shares of common stock by Allegiance in this
       offering,
 
as if such transactions had occurred on January 1, 1998. The as adjusted balance
sheet data is unaudited and gives effect to the issuance of 11,826,000 shares of
common stock by Allegiance in the offering as if such transaction had occurred
on December 31, 1998. Dollar amounts are in thousands, except per share amounts.
 
     Allegiance has generated operating losses and negative cash flow from its
operating activities to date. The selected financial data set forth below should
be read in conjunction with "Management's Discussion and Analysis of Financial
Condition and Results of Operations" and the consolidated financial statements,
including the notes thereto, contained elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                     YEAR ENDED DECEMBER 31, 1998
                                                              -------------------------------------------
                                                                                      PRO FORMA
                                                                            -----------------------------
                                                                ACTUAL      ADJUSTMENTS      AS ADJUSTED
                                                              -----------   -----------      ------------
                                                               (AUDITED)             (UNAUDITED)
<S>                                                           <C>           <C>              <C>
STATEMENT OF OPERATIONS DATA:
Revenues....................................................  $   9,786.2   $       --       $    9,786.2
Operating expenses:
  Network...................................................      9,528.8           --            9,528.8
  Selling, general and administrative.......................     46,089.4           --           46,089.4
  Management ownership allocation charge....................    167,311.9     12,557.7(1)       179,869.6
  Non-cash deferred compensation............................      5,307.2           --            5,307.2
  Depreciation and amortization.............................      9,002.8           --            9,002.8
                                                              -----------   -----------      ------------
        Total operating expenses............................    237,240.1     12,557.7          249,797.8
Loss from operations........................................   (227,453.9)   (12,557.7)        (240,011.6)
Interest income.............................................     19,917.4           --(2)        19,917.4
Interest expense............................................    (38,951.7)   (23,264.0)(3)      (62,215.7)
                                                              -----------   -----------      ------------
Net loss....................................................   (246,488.2)   (35,821.7)        (282,309.9)
Accretion of redeemable convertible preferred stock and
  warrant values............................................    (11,971.4)        (7.4)(4)      (11,978.8)
                                                              -----------   -----------      ------------
Net loss applicable to common stock.........................  $(258,459.6)  $(35,829.1)      $ (294,288.7)
                                                              ===========   ===========      ============
Net loss per share, basic and diluted.......................  $    (10.53)                   $      (4.73)
                                                              ===========                    ============
Weighted average number of shares outstanding, basic and
  diluted...................................................   24,550,346   37,617,208(5)      62,167,554
                                                              ===========   ===========      ============
OTHER FINANCIAL DATA:
EBITDA(6)...................................................  $ (45,832.0)  $       --(1)    $  (45,832.0)
Net cash used in operating activities.......................    (17,269.8)   (13,196.9)(7)      (30,466.7)
Net cash used in investing activities.......................   (319,170.4)    13,196.9(7)      (305,973.5)
Net cash provided by financing activities...................    593,215.5    430,312.5(8)       1,023,528
Capital expenditures(9).....................................    113,538.7           --          113,538.7
</TABLE>
 
                                        4
<PAGE>   8
 
<TABLE>
<CAPTION>
                                                                 AS OF DECEMBER 31, 1998
                                                              ------------------------------
                                                                ACTUAL        AS ADJUSTED(8)
                                                              ----------      --------------
                                                              (AUDITED)        (UNAUDITED)
<S>                                                           <C>             <C>
BALANCE SHEET DATA:
Cash, cash equivalents, short-term investments, and
  restricted short-term
  investments...............................................  $431,434.2       $  861,746.7
Property and equipment, net.................................   144,860.0          144,860.0
Total assets................................................   637,874.3        1,068,186.8
Long-term debt..............................................   471,652.1          471,652.1
Redeemable warrants.........................................     8,634.1            8,634.1
Total stockholders' equity..................................   110,429.6          540,742.1
Total liabilities and stockholders' equity..................   637,874.3        1,068,186.8
</TABLE>
 
<TABLE>
<CAPTION>
                                                                 AS OF DECEMBER 31,
                                                              -------------------------
                                                                 1998          1997
                                                              -----------   -----------
                                                              (UNAUDITED)   (UNAUDITED)
<S>                                                           <C>           <C>
OTHER OPERATIONAL DATA:
Markets served..............................................           9         0
Number of switches deployed.................................           7         0
Central office collocations.................................         101         0
Addressable market (business lines).........................  3.6 million        0
Lines sold..................................................      86,500        20
Lines installed.............................................      47,700         9
Sales force employees.......................................         295         0
Total employees.............................................         649        40
</TABLE>
 
- ---------------
 
 (1) In connection with the initial public offering of common stock, Allegiance
     Telecom, LLC, an entity that owned substantially all of Allegiance's
     outstanding capital stock, was dissolved and its assets, which consisted
     almost entirely of such capital stock, were distributed to the Allegiance
     Telecom, LLC investors in accordance with its limited liability company
     agreement. This agreement provides that the equity allocation between the
     original fund investors and the management investors be 66.7% and 33.3%,
     respectively, based upon the valuation implied by the initial public
     offering of common stock.
 
     Under generally accepted accounting principles, upon consummation of the
     initial public offering of common stock, Allegiance recorded the increase
     in the assets of Allegiance Telecom, LLC allocated to the management
     investors as a $193.5 million increase in additional paid-in capital, of
     which $122.5 million was recorded as a non-cash, non-recurring charge to
     operating expense and $71.0 million was recorded as deferred management
     ownership allocation charge. The deferred charge was amortized at $44.8
     million during 1998 and will be further amortized at $18.8 million, $7.2
     million and $.2 million during 1999, 2000 and 2001, respectively; this is
     the period over which Allegiance has the right to repurchase the
     securities, at the lower of fair market value or the price paid by the
     employee, in the event the management employee's employment with Allegiance
     is terminated. See "Certain Relationships and Related Transactions."
 
     The pro forma gives effect to the additional amortization of the deferred
     management ownership allocation charge.
 
 (2) Pro forma interest income excludes interest income that would have been
     earned on the estimated $69.0 million of the proceeds from the offering of
     our 12 7/8% notes placed in a pledge account to secure and fund the first
     six scheduled interest payments on the 12 7/8% notes.
 
 (3) Reflects $19.8 million of interest expense related to the 12 7/8% notes,
     $.2 million of amortization of the $4.1 million of original issuance
     discount, $.3 million of amortization of the $7.0 million of deferred debt
     issuance cost related to the 12 7/8% notes, $2.9 million of amortization of
     original issuance discount related to the 11 3/4% notes and $.1 million of
     amortization of the $9.8 million of deferred debt issuance cost related to
     the 11 3/4% notes.
 
 (4) Reflects the increase of $7,435 of accretion for the redeemable warrants.
 
                                        5
<PAGE>   9
 
 (5) The pro forma weighted average number of shares outstanding gives effect to
     Allegiance's common stock issued as a result of the initial public offering
     of common stock, the conversion of redeemable convertible preferred stock
     to common stock, and the common stock to be issued by Allegiance in this
     offering.
 
 (6) EBITDA represents earnings before interest, income taxes, depreciation and
     amortization, management ownership allocation charge and non-cash deferred
     compensation. EBITDA is not a measurement of financial performance under
     generally accepted accounting principles, is not intended to represent cash
     flow from operations, and should not be considered as an alternative to net
     loss as an indicator of Allegiance's operating performance or to cash flows
     as a measure of liquidity. Allegiance believes that EBITDA is widely used
     by analysts, investors and other interested parties in the
     telecommunications industry. EBITDA is not necessarily comparable with
     similarly titled measures for other companies.
 
 (7) The pro forma reflects the $13.2 million cash interest payment on May 15
     for the 12 7/8% notes, which would have been funded through a reduction of
     the pledge account.
 
 (8) Reflects $430.3 million of net proceeds from the issuance of common stock
     by Allegiance in this offering.
 
 (9) Reflects cash paid for capital expenditures.
 
                                        6
<PAGE>   10
 
                                  RISK FACTORS
 
     You should carefully consider the following risk factors, as well as other
information in this prospectus, before you decide whether to invest in our
common stock.
 
OUR LIMITED HISTORY OF OPERATIONS MAY NOT BE A RELIABLE BASIS FOR EVALUATING OUR
PROSPECTS
 
     Because of our short operating history, you have limited operating and
financial data which you can use to evaluate our performance and determine
whether you should invest in our common stock. From our inception on April 22,
1997 through December 16, 1997, we were in the development stage of operations.
 
IF WE DO NOT EFFECTIVELY MANAGE RAPID EXPANSION OF OUR BUSINESS, OUR FINANCIAL
CONDITION WILL SUFFER
 
     We are in the early stages of our operations and have only recently begun
to deploy networks in our first 17 target markets. If we are successful in the
implementation of our business plan, we will be rapidly expanding our operations
and providing bundled telecommunications services on a widespread basis. This
rapid expansion may place a significant strain on our management, financial and
other resources. If we fail to manage our growth effectively, we may not be able
to expand our customer base and service offerings as we have planned.
 
OUR SUCCESS DEPENDS ON OUR KEY PERSONNEL AND WE MAY NOT BE ABLE TO REPLACE KEY
EXECUTIVES WHO LEAVE
 
     We are managed by a small number of key executive officers, most notably
Royce J. Holland, our Chairman and Chief Executive Officer. The loss of services
of one or more of these key individuals, particularly Mr. Holland, could
materially and adversely affect our business and our prospects. Most of our
executive officers do not have employment agreements, and we do not maintain key
person life insurance for any of our executive officers. The competition for
qualified personnel in the telecommunications industry is intense. For this
reason, we cannot assure you that we will be able to hire or retain necessary
personnel in the future.
 
WE ARE DEPENDENT ON EFFECTIVE BILLING, CUSTOMER SERVICE AND INFORMATION SYSTEMS
AND WE MAY HAVE DIFFICULTIES IN DEVELOPING THESE SYSTEMS
 
     Sophisticated back office information and processing systems are vital to
our growth and our ability to monitor costs, bill customers, initiate, implement
and track customer orders and achieve operating efficiencies. We cannot assure
you that these systems will be successfully implemented on a timely basis or at
all or will perform as expected because:
 
     - our vendors may fail to deliver proposed products and services in a
       timely and effective manner and at acceptable costs;
 
     - we may fail to adequately identify all of our information and processing
       needs;
 
     - our processing or information systems may fail or be inadequate;
 
     - we may be unable to effectively integrate such products or services;
 
     - we may fail to upgrade systems as necessary; and
 
     - third party vendors may cancel or fail to renew license agreements that
       relate to these systems.
 
WE MAY BE ADVERSELY IMPACTED BY YEAR 2000 ISSUES, MANY OF WHICH ARE BEYOND OUR
CONTROL
 
     The "year 2000" issue generally describes the various problems that may
result from the improper processing of dates and date-sensitive transactions by
computers and other equipment as a result of computer hardware and software
using two digits to identify the year in a date. The failure to process dates
could result in network and system failures or miscalculations causing
disruptions in operations including, among other things, a temporary inability
to process transactions, send invoices or engage in other routine
 
                                        7
<PAGE>   11
 
business activities. A failure of our customers or vendors, including other
telecommunications operators, to cause their software and systems to be year
2000 compliant could have a material adverse effect on us and on our ability to
meet our obligations. Until the year 2000 occurs, we will not know for sure that
all systems will then function adequately. In addition, we are dependent upon
third-party suppliers, including other telecommunications operators, for the
delivery of interconnection and other services and on third-party customers for
the purchase of our services. In many cases, our services and operations require
electronic interfacing with the systems and networks of third-party
telecommunication operators such as the incumbent local exchange carriers. See
"Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Results of Operations -- Impact of Year 2000."
 
WE FACE POTENTIAL CONFLICTS OF INTEREST CAUSED BY FUND INVESTOR CONTROL WHICH
COULD BE DETRIMENTAL TO HOLDERS OF OUR SECURITIES
 
     You should be aware that the investment funds that provided our initial
equity hold a majority of our board seats and a significant amount of our common
stock and that as a result, our direction and future operations may be
controlled by these funds. For a discussion of the voting agreement among our
original fund and management investors regarding the election of nominees to the
board of directors, see the discussion under "Certain Relationships and Related
Transactions." In addition, decisions concerning our operations or financial
structure may present conflicts of interest between these investors and our
management and other holders of our securities, including our notes. In addition
to their investments in us, these investors or their affiliates currently have
significant investments in other telecommunications companies and may in the
future invest in other entities engaged in the telecommunications business or in
related businesses, including entities that compete with us. Conflicts may also
arise in the negotiation or enforcement of arrangements entered into by us and
entities in which these investors have an interest.
 
UNDER CERTAIN CIRCUMSTANCES WE MAY NEED ADDITIONAL CAPITAL TO EXPAND OUR
BUSINESS AND INCREASE REVENUE
 
     We may need additional capital to fund capital expenditures, working
capital, debt service and cash flow deficits during the period in which we are
expanding and developing our business and deploying our networks, services and
systems. We estimate, based on our current business plan, that approximately
$750 to $850 million of capital will be necessary to fund the deployment and
operation of our networks in all of our initial 24 markets to the point at which
operating cash flow from a market will be sufficient to fund such market's
operating and capital expenditures. This amount includes capital expenditures,
working capital and cash flow deficits, but excludes debt service. We have
raised approximately $554 million of capital to date. The actual amount and
timing of our future capital requirements may differ materially from our
estimates as a result of financial, business and other factors many of which are
beyond our control, as well as prevailing economic conditions. See "Management's
Discussion and Analysis of Financial Condition and Results of
Operations -- Liquidity and Capital Resources."
 
     We believe that the proceeds from this offering and borrowings expected to
be available under a senior credit facility, together with our cash on hand,
will be sufficient to pre-fund market deployment in all 24 targeted markets.
However, we will only be able to borrow under the credit facility if we are in
compliance with certain financial covenants. In the event we cannot borrow under
the credit facility we may need to access alternative sources of capital. If we
are unable to do so we may not be able to expand as we expect, which may have an
adverse effect on us.
 
OUR SUBSTANTIAL INDEBTEDNESS COULD MAKE US UNABLE TO SERVICE INDEBTEDNESS AND
MEET OUR OTHER REQUIREMENTS AND COULD ADVERSELY AFFECT OUR FINANCIAL HEALTH
 
     We have a significant amount of debt outstanding and plan to access
additional debt financing to fund our business plan. On December 31, 1998, we
had $471.7 million of outstanding indebtedness and $110.4 million of
stockholders' equity. We anticipate incurring additional indebtedness in the
future, including under our senior secured revolving credit facility that we
closed on April 1, 1999. See the
 
                                        8
<PAGE>   12
 
discussion of this credit facility in the section titled "Description of Certain
Indebtedness -- Revolving Credit Facility."
 
     This level of debt could:
 
     - impair our ability to obtain additional financing for working capital,
       capital expenditures, acquisitions or general corporate purposes;
 
     - require us to dedicate a substantial portion of our cash flow from
       operations to the payment of principal and interest on our indebtedness,
       thereby reducing the funds available for the growth of our networks;
 
     - place us at a competitive disadvantage with those of our competitors who
       do not have as much debt as we do;
 
     - impair our ability to adjust rapidly to changing market conditions; and
 
     - make us more vulnerable if there is a downturn in general economic
       conditions or in our business.
 
     The successful implementation of our business plan is essential for us to
meet our working capital, capital expenditure and debt service requirements.
Allegiance's earnings for the year ended December 31, 1998 were insufficient to
cover fixed charges by approximately $249.3 million. After giving pro forma
effect to the increase in interest expense resulting from the issuance of the
12 7/8% notes and the 11 3/4% notes and giving effect to the $12.6 million of
management ownership allocation charge which would have been recorded,
Allegiance's earnings would have been insufficient to cover fixed charges by
approximately $285.1 million for the year ended December 31, 1998. We cannot
assure you that we will be able to meet our working capital, capital expenditure
and debt service requirements.
 
LIMITATIONS IMPOSED BY RESTRICTIVE COVENANTS COULD LIMIT HOW WE CONDUCT BUSINESS
AND A DEFAULT UNDER OUR INDENTURES AND FINANCING AGREEMENTS COULD SIGNIFICANTLY
IMPACT OUR ABILITY TO REPAY OUR INDEBTEDNESS
 
     Our indentures and the agreements entered into in connection with our
initial equity funding contain covenants that restrict our ability to:
 
     - incur additional indebtedness;
 
     - pay dividends and make other distributions;
 
     - prepay subordinated indebtedness;
 
     - make investments and other restricted payments;
 
     - enter into sale and leaseback transactions;
 
     - create liens;
 
     - sell assets; and
 
     - engage in certain transactions with affiliates.
 
     Our current and future financing arrangements, including the senior secured
revolving credit facility discussed in the section titled "Description of
Certain Indebtedness -- Revolving Credit Facility," contain and will continue to
contain similar or more restrictive covenants, as well as other covenants that
will require us to maintain specified financial ratios and satisfy financial
tests. As a result of these restrictions, we are limited in how we conduct
business and we may be unable to raise additional debt or equity financing to
operate during general economic or business downturns, to compete effectively or
to take advantage of new business opportunities. This may affect our ability to
generate revenues and make profits. Without sufficient revenues and cash, we may
not be able to pay interest and principal on our indebtedness.
 
                                        9
<PAGE>   13
 
     Our failure to comply with the covenants and restrictions contained in our
indentures and other financing agreements could lead to a default under the
terms of these agreements. If such a default occurs, the other parties to such
agreements could declare all amounts borrowed and all amounts due under other
instruments that contain provisions for cross-acceleration or cross-default due
and payable. In addition, lenders under our future financing arrangements could
terminate their commitments to lend to us. If that occurs, we cannot assure you
that we would be able to make payments on our indebtedness, meet our working
capital and capital expenditure requirements, or that we would be able to find
additional alternative financing. Even if we could obtain additional alternative
financing, we cannot assure you that it would be on terms that are favorable or
acceptable to us.
 
WE MAY NOT HAVE THE FUNDS NECESSARY TO FINANCE THE CHANGE OF CONTROL OFFER WHICH
MAY BE REQUIRED BY OUR INDENTURES
 
     Our indentures provide that upon a change of control, each note holder will
have the right to require us to purchase all or a portion of such holder's
notes. We would be required to purchase the notes at a purchase price of 101% of
the accreted value of the 11 3/4% notes and 101% of the principal amount of the
12 7/8% notes, plus any accrued and unpaid interest to the date of repurchase.
It is possible that we will not have sufficient funds at that time to repurchase
our notes.
 
IF WE DO NOT INTERCONNECT WITH OUR PRIMARY COMPETITORS, THE INCUMBENT LOCAL
EXCHANGE CARRIERS, OUR BUSINESS WILL BE ADVERSELY AFFECTED
 
     Many new carriers, including Allegiance, have experienced difficulties in
working with the incumbent local exchange carriers with respect to initiating,
interconnecting, and implementing the systems used by these new carriers to
order and receive unbundled network elements and wholesale services and locating
the new carriers' equipment in the offices of the incumbent local exchange
carriers. As a new carrier, we must coordinate with incumbent local exchange
carriers so that we can provide local service to customers on a timely and
competitive basis. The Telecommunications Act created incentives for regional
Bell operating companies to cooperate with new carriers and permit access to
their facilities by denying such companies the ability to provide in-region long
distance services until they have satisfied statutory conditions designed to
open their local markets to competition. The regional Bell operating companies
in our markets are not yet permitted by the FCC to offer long distance services.
These companies may not be accommodating to us once they are permitted to offer
long distance service. If we cannot obtain the cooperation of a regional Bell
operating company in a region, whether or not it has been authorized to offer
long distance service, our ability to offer local services in such region on a
timely and cost-effective basis will be adversely affected.
 
IF WE DO NOT OBTAIN PEERING ARRANGEMENTS WITH INTERNET SERVICE PROVIDERS, THE
PROFITABILITY OF OUR INTERNET ACCESS SERVICES WILL SUFFER
 
     The profitability of our Internet access services, and related services
such as Web site hosting, may be adversely affected if we are unable to obtain
"peering" arrangements with Internet service providers. In the past, major
Internet service providers routinely exchanged traffic with other Internet
service providers that met technical criteria on a "peering" basis, meaning that
each Internet service provider accepted traffic routed to Internet addresses on
their system from their "peers" on a reciprocal basis, without payment of
compensation. However, since 1997 UUNET Technologies, Inc., the largest Internet
service provider, has been greatly restricting the use of peering arrangements
with other providers and has been imposing charges for accepting traffic from
providers other than its "peers." Other major Internet service providers have
adopted similar policies. We do not currently have any peering arrangements and
cannot assure you that we will be able to negotiate "peer" status with any of
the major nationwide Internet service providers in the future, or that we will
be able to terminate traffic on Internet service providers' networks at
favorable prices.
 
                                       10
<PAGE>   14
 
OUR OFFERING OF LONG DISTANCE SERVICES IS AFFECTED BY OUR ABILITY TO ESTABLISH
EFFECTIVE RESALE AGREEMENTS
 
     As part of our "one-stop shopping" offering of bundled telecommunications
services to our customers, we offer long distance services. We have relied and
will continue to rely on other carriers to provide transmission and termination
services for all of our long distance traffic. We will continue to enter into
resale agreements with long distance carriers to provide us with transmission
services. Such agreements typically provide for the resale of long distance
services on a per-minute basis and may contain minimum volume commitments.
Negotiation of these agreements involves estimates of future supply and demand
for transmission capacity as well as estimates of the calling pattern and
traffic levels of our future customers. If we fail to meet our minimum volume
commitments, we may be obligated to pay underutilization charges and if we
underestimate our need for transmission capacity, we may be required to obtain
capacity through more expensive means.
 
OUR PRINCIPAL COMPETITORS FOR LOCAL SERVICES, THE INCUMBENT LOCAL EXCHANGE
CARRIERS, AND POTENTIAL ADDITIONAL COMPETITORS, HAVE ADVANTAGES THAT MAY
ADVERSELY AFFECT OUR ABILITY TO COMPETE WITH THEM
 
     The telecommunications industry is highly competitive. Many of our current
and potential competitors in the local market have financial, technical,
marketing, personnel and other resources, including brand name recognition,
substantially greater than ours, as well as other competitive advantages over
us. In each of the markets targeted by us, we will compete principally with the
incumbent local exchange carrier serving that area and they enjoy advantages
that may adversely affect our ability to compete with them. Incumbent local
exchange carriers are established providers of local telephone services to all
or virtually all telephone subscribers within their respective service areas.
Incumbent local exchange carriers also have long-standing relationships with
federal and state regulatory authorities. FCC and state administrative decisions
and initiatives provide the incumbent local exchange carriers with pricing
flexibility for their:
 
     - private lines, which are private, dedicated telecommunications
       connections between customers;
 
     - special access services, which are dedicated lines from a customer to a
       long distance company provided by the local phone company; and
 
     - switched access services, which refers to the call connection provided by
       the local phone company's switch between a customer's phone and the long
       distance company's switch.
 
     In addition, with respect to competitive access services, such as special
access services as opposed to switched access services, the FCC is considering
allowing incumbent local exchange carriers increased pricing flexibility and
deregulation for such access services either automatically or after certain
competitive levels are reached. If the incumbent local exchange carriers are
allowed by regulators to offer discounts to large customers through contract
tariffs, engage in aggressive volume and term discount pricing practices for
their customers, and/or seek to charge competitors excessive fees for
interconnection to their networks, competitors such as us could be materially
adversely affected. If future regulatory decisions afford the incumbent local
exchange carriers increased pricing flexibility or other regulatory relief, such
decisions could also have a material adverse effect on competitors such as us.
 
     We also face, and expect to continue to face, competition in the local
market from other current and potential market entrants, including long distance
carriers seeking to enter, reenter or expand entry into the local exchange
marketplace such as AT&T, MCI WorldCom and Sprint, and from other competitive
local exchange carriers, resellers, competitive access providers, cable
television companies, electric utilities, microwave carriers, wireless telephone
system operators and private networks built by large end users. In addition, the
development of new technologies could give rise to significant new competitors
in the local market.
 
                                       11
<PAGE>   15
 
SIGNIFICANT COMPETITION IN PROVIDING LONG DISTANCE AND INTERNET SERVICES COULD
REDUCE THE DEMAND FOR AND PROFITABILITY OF OUR SERVICES
 
     We also face significant competition in providing long distance and
Internet services. Many of these competitors have greater financial,
technological, marketing, personnel and other resources than those available to
us.
 
     The long distance telecommunications market has numerous entities competing
for the same customers and a high average turnover rate, as customers frequently
change long distance providers in response to the offering of lower rates or
promotional incentives. Prices in the long distance market have declined
significantly in recent years and are expected to continue to decline. We face
competition from large carriers such as AT&T, MCI WorldCom and Sprint and many
smaller long distance carriers. Other competitors are likely to include regional
Bell operating companies providing long distance services outside of their local
service area and, with the removal of regulatory barriers, long distance
services within such local service areas, other competitive local exchange
carriers, microwave and satellite carriers and private networks owned by large
end users. We may also increasingly face competition from companies offering
local and long distance data and voice services over the Internet. Such
companies could enjoy a significant cost advantage because they do not currently
pay many of the charges or fees that we have to pay. In addition, in June 1998,
Sprint announced its intention to offer voice, data and video services over its
nationwide asynchronous transfer mode network, which Sprint anticipates will
significantly reduce its cost to provide such services. Sprint plans to bill its
customers based upon the amount of traffic carried, irrespective of the time
required to send the traffic or the traffic's destination.
 
     The Internet services market is highly competitive and we expect that
competition will continue to intensify. Our competitors in this market include
Internet service providers, other telecommunications companies, online services
providers and Internet software providers.
 
OUR NEED TO COMPLY WITH EXTENSIVE GOVERNMENT REGULATION CAN INCREASE OUR COSTS
AND SLOW OUR GROWTH
 
     Our networks and the provision of telecommunications services are subject
to significant regulation at the federal, state and local levels. Delays in
receiving required regulatory approvals or the enactment of new adverse
regulation or regulatory requirements may slow our growth and have a material
adverse effect upon us.
 
     The FCC exercises jurisdiction over us with respect to interstate and
international services. We must obtain, and have obtained through our
subsidiary, Allegiance Telecom International, Inc., prior FCC authorization for
installation and operation of international facilities and the provision,
including by resale, of international long distance services. Additionally, we
file publicly available documents detailing our services, equipment and pricing,
also known as "tariffs," with the FCC for both international and domestic
long-distance services.
 
     State regulatory commissions exercise jurisdiction over us because we
provide intrastate services. We are required to obtain regulatory authorization
and/or file tariffs at state agencies in most of the states in which we operate.
If and when we seek to build our own network segments, local authorities
regulate our access to municipal rights-of-way. Constructing a network is also
subject to numerous local regulations such as building codes and licensing. Such
regulations vary on a city by city and county by county basis.
 
     Regulators at both the federal and state level require us to pay various
fees and assessments, file periodic reports, and comply with various rules
regarding the contents of our bills, protection of subscriber privacy, and
similar matters on an on-going basis.
 
     We cannot assure you that the FCC or state commissions will grant required
authority or refrain from taking action against us if we are found to have
provided services without obtaining the necessary authorizations, or to have
violated other requirements of their rules and orders. Regulators or others
could challenge our compliance with applicable rules and orders. Such challenges
could cause us to incur substantial legal and administrative expenses.
                                       12
<PAGE>   16
 
DEREGULATION OF THE TELECOMMUNICATIONS INDUSTRY INVOLVES UNCERTAINTIES, AND THE
RESOLUTION OF THESE UNCERTAINTIES COULD ADVERSELY AFFECT OUR BUSINESS
 
     The Telecommunications Act provides for a significant deregulation of the
domestic telecommunications industry, including the local exchange, long
distance and cable television industries. The Telecommunications Act remains
subject to judicial review and additional FCC rulemaking, and thus it is
difficult to predict what effect the legislation will have on us and our
operations. There are currently many regulatory actions underway and being
contemplated by federal and state authorities regarding interconnection pricing
and other issues that could result in significant changes to the business
conditions in the telecommunications industry. We cannot assure you that these
changes will not have a material adverse effect upon us.
 
THE REGULATION OF INTERCONNECTION WITH INCUMBENT LOCAL EXCHANGE CARRIERS
INVOLVES UNCERTAINTIES, AND THE RESOLUTION OF THESE UNCERTAINTIES COULD
ADVERSELY AFFECT OUR BUSINESS
 
     Although the incumbent local exchange carriers are required under the
Telecommunications Act to unbundle and make available elements of their network
and permit us to purchase only the origination and termination services that we
need, thereby decreasing our operating expenses, such unbundling may not be done
as quickly as we require and may be priced higher than we expect. This is
important because we rely on the facilities of these other carriers to connect
to our high capacity digital switches so that we can provide services to our
customers. Our ability to obtain these interconnection agreements on favorable
terms, and the time and expense involved in negotiating them, can be adversely
affected by legal developments.
 
     A recent Supreme Court decision vacated a FCC rule determining which
network elements the incumbent local exchange carriers must provide to
competitors on an unbundled basis. We expect that the FCC will conduct a
rulemaking to adopt new standards for unbundling of network elements in
conformance with this decision. The implementation of these and other FCC rules
may lead to further litigation. This may complicate our interconnection
negotiations, and may adversely affect our existing agreements and operations.
 
WE COULD LOSE REVENUE IF CALLS TO INTERNET SERVICE PROVIDERS ARE TREATED AS LONG
DISTANCE INTERSTATE CALLS
 
     We believe that other local exchange carriers should have to compensate us
when their customers place calls to Internet service providers who are our
customers. Most incumbent local exchange carriers disagree. Internet service
providers are among our target customers, and decisions providing that other
carriers do not have to compensate us for these calls could limit our ability to
service this group of customers profitably.
 
     For all other local calls, it is clear that the telecommunications company
whose customer calls a customer of a second telecommunications company must
compensate the second company. This is known as reciprocal compensation. This
rule does not apply to long distance interstate calls and the FCC in its
Declaratory Ruling of February 26, 1999, determined that Internet service
provider traffic is interstate for jurisdictional purposes, but that its current
rules neither require nor prohibit the payment of reciprocal compensation for
such calls. In the absence of a federal rule, the FCC determined that state
commissions have authority to interpret and enforce the reciprocal compensation
provisions of existing interconnection agreements, and to determine the
appropriate treatment of Internet service provider traffic in arbitrating new
agreements.
 
THE REGULATION OF ACCESS CHARGES INVOLVES UNCERTAINTIES, AND THE RESOLUTION OF
THESE UNCERTAINTIES COULD ADVERSELY AFFECT OUR BUSINESS
 
     To the extent we provide long-distance, often referred to as
"interexchange," telecommunications service, we are required to pay access
charges to other local exchange carriers when we use the facilities of those
companies to originate or terminate interexchange calls. As a competitive local
exchange carrier, we
                                       13
<PAGE>   17
 
also provide access services to other long distance service providers. The
interstate access charges of incumbent local exchange carriers are subject to
extensive regulation by the FCC, while those of competitive local exchange
carriers are subject to a lesser degree of FCC regulation, but remain subject to
the requirement that all charges be just, reasonable, and not unreasonably
discriminatory. Disputes have arisen regarding the regulation of access charges
and these may be resolved adversely to us.
 
     The FCC has made major changes in the interstate access charge structure.
The manner in which the FCC implements and monitors these increased pricing
flexibility changes could have a material adverse effect on our ability to
compete in providing interstate access services.
 
     Some interexchange carriers, including AT&T, have also asked the FCC to
take regulatory action to prevent competitive local exchange carriers from
charging allegedly "excessive" access charges. Although no complaints have been
filed against us, we do provide access service to interexchange carriers and we
could be subject in the future to allegations that our charges for this service
are unjust and unreasonable. In that event, we would have to provide the FCC
with an explanation of how we set our rates and justify them as reasonable. We
can give no assurance that the FCC will accept our rates as reasonable. If our
rates are reduced by regulatory order, this could have a material adverse effect
on our profitability.
 
IF WE DO NOT CONTINUALLY ADAPT TO TECHNOLOGICAL CHANGE, WE COULD LOSE CUSTOMERS
AND MARKET SHARE
 
     The telecommunications industry is subject to rapid and significant changes
in technology, and we rely on outside vendors for the development of and access
to new technology. The effect of technological changes on our business cannot be
predicted. We believe our future success will depend, in part, on our ability to
anticipate or adapt to such changes and to offer, on a timely basis, services
that meet customer demands. We cannot assure you that we will obtain access to
new technology on a timely basis or on satisfactory terms. Any failure by us to
obtain new technology could cause us to lose customers and market share.
 
WE HAVE APPLIED FOR, BUT NOT YET RECEIVED, ASSURANCE FROM THE SEC REGARDING OUR
STATUS UNDER THE INVESTMENT COMPANY ACT AND IF WE ARE SUBJECT TO THE INVESTMENT
COMPANY ACT, IT COULD ADVERSELY AFFECT OUR FINANCING ACTIVITIES AND FINANCIAL
RESULTS
 
     Allegiance currently has substantial short-term investments, pending the
deployment of our capital in the pursuit of building our business. See
"Capitalization" and "Use of Proceeds." This may result in Allegiance being
deemed as an "investment company" under the Investment Company Act of 1940. This
statute requires the registration of, and imposes various substantive
restrictions on, certain companies that are, or hold themselves out as being,
engaged primarily, or propose to engage primarily in, the business of investing,
reinvesting or trading in securities, or that fail certain statistical tests
regarding composition of assets and sources of income even though they do not
intend to be primarily engaged in the businesses of investing, reinvesting,
owning, holding or trading securities.
 
     Allegiance is primarily engaged in a business other than investing,
reinvesting, owning, holding or trading securities and, therefore, is not an
investment company within the meaning of this statute. While we believe this
means we are not an investment company within the meaning of that law, we have
been able to also rely on a safe harbor in that law for certain transient or
temporary investment companies. However, this exemption is only available to
companies for a one-year period and that one-year period terminated in January
1999. We have applied to the SEC for a one-year exemptive order declaring that
Allegiance is not an investment company and not required to register under this
statute. We have not yet received such an order, and it is possible that we will
not ultimately be successful in receiving such an order.
 
     If we were required to register as an investment company under the
Investment Company Act, we would become subject to substantial regulation with
respect to our capital structure, management, operations, transactions with
affiliated persons and other matters. To avoid having to register as an
investment company, we may have to apply for an extension to our one-year
exemption, if granted, or invest a portion of our liquid assets in cash and
demand deposits instead of short-term securities. The
                                       14
<PAGE>   18
 
extent to which we will have to do so will depend on the composition and value
of our total assets at that time. Having to register as an investment company or
having to invest a material portion of our liquid assets in cash and demand
deposits to avoid such registration, could have a material adverse effect on our
business, financial condition and results of operations.
 
FUTURE SALES OF OUR STOCK BY EXISTING STOCKHOLDERS MAY ADVERSELY AFFECT OUR
STOCK PRICE
 
     After this offering, we will have approximately 62,215,115 shares of common
stock outstanding. While certain of these shares are "restricted securities"
under the federal securities laws, such shares are or will be eligible for sale
subject to restrictions as to timing, manner, volume, notice and the
availability of current public information regarding Allegiance. See "Shares
Eligible for Future Sale." Sales of substantial amounts of stock in the public
market, or the perception that sales could occur, could depress the prevailing
market price for our stock. Sales may also make it more difficult for us to sell
equity securities or equity-related securities in the future at a time and price
that we deem appropriate.
 
ANTI-TAKEOVER PROVISIONS IN ALLEGIANCE'S CHARTER AND BYLAWS COULD LIMIT OUR
SHARE PRICE AND DELAY A CHANGE OF MANAGEMENT
 
     Our certificate of incorporation and by-laws contain provisions that could
make it more difficult or even prevent a third party from acquiring Allegiance
without the approval of our incumbent board of directors. See "Description of
Capital Stock."
 
OUR FORWARD-LOOKING STATEMENTS MAY MATERIALLY DIFFER FROM ACTUAL EVENTS OR
RESULTS
 
     This prospectus contains "forward-looking statements," which you generally
can identify by our use of forward-looking words such as "believes," "expects,"
"may," "will," "should" or "anticipates" or the negative or other variations of
such terms or comparable terminology, or by discussion of strategy that involve
risks and uncertainties. We often use these types of statements when discussing
our plans and strategies, our anticipation of revenues from designated markets,
and statements regarding the development of our businesses, the markets for our
services and products, our anticipated capital expenditures, operations support
systems, changes in regulatory requirements and other statements contained in
this prospectus regarding matters that are not historical facts.
 
     We caution you that these forward-looking statements are only predictions
and estimates regarding future events and circumstances. We cannot assure you
that we will achieve the future results reflected in these statements. The risks
we face that could cause us not to achieve these results include, but are not
limited to our ability to do the following in a timely manner, at reasonable
costs and on satisfactory terms and conditions:
 
     - successfully market our services to current and new customers;
 
     - interconnect with and develop cooperative working relationships with
       incumbent local exchange carriers;
 
     - develop efficient operations support systems and other back office
       systems;
 
     - successfully and efficiently transfer new customers to our networks and
       access new geographic markets;
 
     - identify, finance and complete suitable acquisitions;
 
     - borrow under our senior credit facility;
 
     - install new switching facilities and other network equipment; and
 
     - obtain leased fiber optic line capacity, rights-of-way, building access
       rights and any required governmental authorizations, franchises and
       permits.
 
                                       15
<PAGE>   19
 
     Regulatory, legislative and judicial developments could also cause actual
results to differ materially from the future results reflected in such
forward-looking statements. You should consider all of our subsequent written
and oral forward-looking statements only in light of such cautionary statements.
You should not place undue reliance on these forward-looking statements and you
should understand that they speak only as of the dates we make them.
 
                                USE OF PROCEEDS
 
     The net proceeds to Allegiance from the sale of the 11,826,000 shares of
common stock in this offering at the assumed public offering price of $38.00 per
share are estimated to be approximately $430.3 million (approximately $510.6
million if the underwriters' over-allotment option is exercised in full), after
deducting underwriting discounts and commissions and estimated offering expenses
payable by Allegiance. We intend to use the net proceeds from this offering and
our previous financing activities primarily to fund the costs of deploying
networks in all 24 of our targeted markets. We may also use a portion of the net
proceeds for other general corporate purposes, which may include acquisitions.
See "Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Liquidity and Capital Resources."
 
     Allegiance will not receive any of the proceeds from the sale of common
stock by the selling stockholders.
 
                                DIVIDEND POLICY
 
     We do not anticipate paying any cash dividends in the foreseeable future.
Any future determination to pay dividends will be at the discretion of our board
of directors and will be dependent upon then existing conditions, including our
financial condition, results of operations, contractual restrictions, capital
requirements, business prospects, and other factors our board of directors deems
relevant. In addition, our current financing agreements effectively prohibit us
from paying cash dividends for the foreseeable future.
 
                          MARKET PRICE OF COMMON STOCK
 
     Allegiance's common stock is traded on the Nasdaq National Market under the
symbol "ALGX." Allegiance completed the initial public offering of its common
stock on July 1, 1998. The following table sets forth, for the periods
indicated, the high and low sales prices for the common stock as reported by the
Nasdaq National Market.
 
<TABLE>
<CAPTION>
                                                              COMMON STOCK PRICE
                                                              -------------------
                                                                HIGH        LOW
                                                              --------    -------
<S>                                                           <C>         <C>
Year ended December 31, 1998:
  Third quarter (from July 1, 1998).........................  $15.688     $6.250
  Fourth quarter............................................   13.375      5.000
Year ended December 31, 1999:
  First quarter.............................................   31.000     11.563
  Second quarter (through April 14, 1999)...................   46.000     25.375
</TABLE>
 
     A recent reported last sale price for Allegiance common stock, as reported
on the Nasdaq National Market, is set forth on the cover page of this
prospectus. On April 9, 1999, we had approximately 130 holders of record of
common stock.
 
                                       16
<PAGE>   20
 
                                    DILUTION
 
     The net tangible book value of Allegiance as of December 31, 1998 was
approximately $110.4 million or $2.19 per share. Net tangible book value per
share represents the amount of Allegiance's total tangible assets less total
liabilities, divided by the total number of shares of common stock outstanding.
After giving effect to the sale by Allegiance of 11,826,000 shares of common
stock offered hereby at an assumed offering price of $38.00 per share and after
deducting underwriting discounts and commissions and estimated offering expenses
of $1.61 per share, the net tangible book value at December 31, 1998 would have
been approximately $540.7 million, or $8.70 per share. This represents an
immediate increase in net tangible book value of $6.51 per share to existing
stockholders and an immediate dilution of $29.30 per share to new investors in
this offering, as illustrated by the following table:
 
<TABLE>
<S>                                                           <C>      <C>
Assumed public offering price per share.....................           $38.00
  Net tangible book value per share before the offering.....  $2.19
  Increase per share attributable to new investors..........   6.51
                                                              -----
Pro forma net tangible book value per share after the
  offering..................................................             8.70
                                                                       ------
Net tangible book value dilution per share to new
  investors.................................................           $29.30
                                                                       ======
</TABLE>
 
                                       17
<PAGE>   21
 
                                 CAPITALIZATION
 
     The following table sets forth the capitalization of Allegiance as of
December 31, 1998 and as adjusted to reflect the sale of 11,826,000 shares of
common stock pursuant to this offering, assuming an offering price of $38.00 and
that the underwriters' over-allotment option is not exercised. This table should
be read in conjunction with the consolidated financial statements and related
notes and "Management's Discussion and Analysis of Financial Condition and
Results of Operations," appearing elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                AS OF DECEMBER 31, 1998
                                                              ---------------------------
                                                                ACTUAL       AS ADJUSTED
                                                              -----------    ------------
                                                               (AUDITED)     (UNAUDITED)
                                                                (DOLLARS IN THOUSANDS)
<S>                                                           <C>            <C>
Cash, cash equivalents and short-term investments(1)........  $ 405,891.4    $  836,203.9
Short-term investments, restricted..........................     25,542.8        25,542.8
                                                              -----------    ------------
          Total cash, cash equivalents, short-term
            investments and restricted short-term
            investments.....................................  $ 431,434.2    $  861,746.7
                                                              ===========    ============
Long-term debt:
  11 3/4% senior discount notes, at accreted value..........  $ 270,526.1    $  270,526.1
  12 7/8% senior notes, at accreted value...................    201,018.6       201,018.6
  Other.....................................................        107.4           107.4
                                                              -----------    ------------
          Total long-term debt..............................  $ 471,652.1    $  471,652.1
                                                              ===========    ============
Redeemable warrants.........................................      8,634.1         8,634.1
Stockholders' equity:
  Preferred stock, $.01 par value, 1,000,000 shares
     authorized, 0 shares issued and outstanding at December
     31, 1998 and as adjusted...............................           --              --
  Common stock, $.01 par value, 150,000,000 shares
     authorized, 50,341,554 and 62,167,554 shares issued and
     outstanding at December 31, 1998 and as adjusted,
     respectively(1)........................................        503.4           621.7
Additional paid-in capital(1)...............................    416,729.9       846,924.1
Deferred compensation.......................................    (14,617.3)      (14,617.3)
Deferred management ownership allocation charge.............    (26,224.7)      (26,224.7)
Accumulated deficit.........................................   (265,961.7)     (265,961.7)
                                                              -----------    ------------
          Total stockholders' equity........................    110,429.6       540,742.1
                                                              -----------    ------------
            Total capitalization............................  $ 590,715.8    $1,021,028.3
                                                              ===========    ============
</TABLE>
 
- ---------------
 
(1) As adjusted reflects the estimated net proceeds of $430.3 million from the
    issuance of common stock by Allegiance in this offering.
 
                                       18
<PAGE>   22
 
                            SELECTED FINANCIAL DATA
 
     The selected consolidated financial data presented below as of and for the
year ended December 31, 1998 and as of and for the period from inception on
April 22, 1997 through December 31, 1997 were derived from the audited
consolidated financial statements of Allegiance and the notes thereto contained
elsewhere in this prospectus, which statements have been audited by Arthur
Andersen LLP, independent public accountants. Dollar amounts are in thousands,
except per share amounts.
 
     From Allegiance's formation in April 1997 until December 16, 1997,
Allegiance was in the development stage. Allegiance has generated operating
losses and negative cash flow from its operating activities to date. The
selected financial data set forth below should be read in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the consolidated financial statements, including the notes
thereto, contained elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                                     PERIOD FROM
                                                                                    INCEPTION ON
                                                                                   APRIL 22, 1997
                                                                YEAR ENDED             THROUGH
                                                             DECEMBER 31, 1998    DECEMBER 31, 1997
                                                             -----------------    -----------------
<S>                                                          <C>                  <C>
STATEMENT OF OPERATIONS DATA:
Revenues...................................................     $   9,786.2          $       0.4
Operating expenses:
  Network..................................................         9,528.8                151.2
  Selling, general and administrative......................        46,089.4              3,425.9
  Management ownership allocation charge(1)................       167,311.9                   --
  Non-cash deferred compensation...........................         5,307.2                209.9
  Depreciation and amortization............................         9,002.8                 12.7
                                                                -----------          -----------
          Total operating expenses.........................       237,240.1              3,799.7
Loss from operations.......................................      (227,453.9)            (3,799.3)
Interest income............................................        19,917.4                111.4
Interest expense...........................................       (38,951.7)                  --
                                                                -----------          -----------
Net loss...................................................      (246,488.2)            (3,687.9)
Accretion of redeemable convertible preferred stock and
  warrant values...........................................       (11,971.4)            (3,814.2)
                                                                -----------          -----------
Net loss applicable to common stock........................     $(258,459.6)         $  (7,502.1)
                                                                ===========          ===========
Net loss per share, basic and diluted......................     $    (10.53)         $(17,610.68)
                                                                ===========          ===========
Weighted average number of shares outstanding, basic and
  diluted..................................................      24,550,346                  426
                                                                ===========          ===========
OTHER FINANCIAL DATA:
EBITDA(2)..................................................     $ (45,832.0)         $  (3,576.7)
Net cash used in operating activities......................       (17,269.8)            (1,942.9)
Net cash used in investing activities......................      (319,170.4)           (21,926.0)
Net cash provided by financing activities..................       593,215.5             29,595.3
Capital expenditures(3)....................................       113,538.7             21,926.0
</TABLE>
 
                                       19
<PAGE>   23
 
<TABLE>
<CAPTION>
                                                                 AS OF DECEMBER 31,
                                                              ------------------------
                                                                 1998          1997
                                                              -----------    ---------
<S>                                                           <C>            <C>
BALANCE SHEET DATA:
Cash, cash equivalents, short-term investments, and
  restricted short-term investments.........................  $ 431,434.2    $ 5,726.4
Property and equipment, net.................................    144,860.0     23,899.9
Total assets................................................    637,874.3     30,047.0
Long-term debt..............................................    471,652.1           --
Redeemable cumulative convertible preferred stock -- 0 and
  40,498,062 shares issued and outstanding at December 31,
  1998 and December 31, 1997, respectively..................           --     33,409.4
Redeemable warrants.........................................      8,634.1           --
Total stockholders' equity (deficit)........................    110,429.6     (7,292.1)
Total liabilities and stockholders' equity (deficit)........    637,874.3     30,047.0
</TABLE>
 
- ---------------
 
 (1) In connection with the initial public offering of common stock, Allegiance
     Telecom, LLC, an entity that owned substantially all of Allegiance's
     outstanding capital stock, was dissolved and its assets, which consisted
     almost entirely of such capital stock, were distributed to the Allegiance
     Telecom, LLC investors in accordance with its limited liability company
     agreement. This agreement provides that the equity allocation between the
     original fund investors and the management investors be 66.7% and 33.3%,
     respectively, based upon the valuation implied by the initial public
     offering of common stock.
 
     Under generally accepted accounting principles, upon consummation of the
     initial public offering of common stock, Allegiance recorded the increase
     in the assets of Allegiance Telecom, LLC allocated to the management
     investors as a $193.5 million increase in additional paid-in capital, of
     which $122.5 million was recorded as a non-cash, non-recurring charge to
     operating expense and $71.0 million was recorded as deferred management
     ownership allocation charge. The deferred charge was amortized at $44.8
     million during 1998 and will be further amortized at $18.8 million, $7.2
     million and $.2 million during 1999, 2000 and 2001, respectively; this is
     the period over which Allegiance has the right to repurchase the
     securities, at the lower of fair market value or the price paid by the
     employee, in the event the management employee's employment with Allegiance
     is terminated. See "Certain Relationships and Related Transactions."
 
 (2) EBITDA represents earnings before interest, income taxes, depreciation and
     amortization, management ownership allocation charge and non-cash deferred
     compensation. EBITDA is not a measurement of financial performance under
     generally accepted accounting principles, is not intended to represent cash
     flow from operations, and should not be considered as an alternative to net
     loss as an indicator of Allegiance's operating performance or to cash flows
     as a measure of liquidity. Allegiance believes that EBITDA is widely used
     by analysts, investors and other interested parties in the
     telecommunications industry. EBITDA is not necessarily comparable with
     similarly titled measures for other companies.
 
 (3) Reflects cash paid for capital expenditures.
 
                                       20
<PAGE>   24
 
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
OVERVIEW
 
     Allegiance is a competitive local exchange carrier ("CLEC"), seeking to be
a premier provider of telecommunications services to business, government and
other institutional users in major metropolitan areas across the United States.
Allegiance offers an integrated set of telecommunications products and services
including local exchange, local access, domestic and international long
distance, data and a full suite of Internet services. Its principal competitors
are incumbent local exchange carriers ("ILECs"), such as the regional Bell
operating companies and GTE Corporation operating units.
 
     Allegiance is developing its networks throughout the United States using
what it refers to as a "smart build" approach. In contrast to the traditional
network build-out strategy under which carriers install their own
telecommunications switch in each market and then construct their own fiber
optic networks to reach customers, Allegiance installs its own switch in each
market but then leases other elements of the network from the ILECs. The smart
build strategy specifically involves:
 
     - leasing existing ILEC copper wire connections throughout a local market
       area, also called the "local loop," which connect customers to the
       central offices or "hubs" of an ILEC network, and
 
     - installing, or physically locating, transmission equipment in these
       central offices to route customer traffic through them to Allegiance's
       own switch.
 
     Locating equipment at ILEC facilities, also known as "collocation," is
central to the success of the smart build strategy. By collocating, Allegiance
has the ability to lease, on a monthly or long-term basis, local loop and other
network elements owned by the ILEC. This enables Allegiance to reach a wide
range of customers without having to build network connections to each one of
them.
 
     Management believes that the smart build approach offers a number of
competitive advantages over the traditional build-out strategy by allowing
Allegiance to:
 
     - accelerate market entry by nine to eighteen months through eliminating or
       at least deferring the need for city franchises, rights-of-way and
       building access;
 
     - reduce initial capital expenditures in each market, allowing Allegiance
       to focus its initial capital resources on the critical areas of sales,
       marketing, and operations support systems, instead of on constructing
       extensive fiber optic networks to each customer;
 
     - improve return on capital by generating revenue with a smaller capital
       investment;
 
     - defer capital expenditures for network assets to the time when revenue
       generated by customer demand is available to finance such expenditures;
       and
 
     - address attractive service areas selectively throughout target markets
       and not just in those areas where Allegiance owns network transmission
       facilities.
 
     Allegiance believes that its smart build approach allows it to reduce its
up-front capital expenditures to approximately 25% of the total capital
expenditures required to develop such a network as compared with initial capital
expenditures of approximately 50% under traditional build out models. The level
of "up-front" capital required to be spent by Allegiance to develop a network
will vary depending on a number of factors. These factors include: the size and
geography of the market, the cost of development of Allegiance's network in each
market, the degree of penetration of the market, the extent of price and service
competition for telecommunications services, regulatory and technological
developments and Allegiance's ability to negotiate favorable prices for
purchases of equipment.
 
     Once traffic volume justifies further investment, we may lease unused fiber
to which Allegiance adds its own electronic transmission equipment or construct
our own fiber network. This unused fiber is known
 
                                       21
<PAGE>   25
 
as "dark fiber" because no light is transmitted through it while it is unused.
Allegiance believes that dark fiber is readily available in most major markets.
See "-- Results of Operations" for a discussion of our leasing of dark fiber.
 
     Allegiance has rapidly deployed its networks since commencing service in
December 1997 and was operating in nine markets across the United States as of
the end of 1998, and thirteen as of April 14, 1999. Allegiance has had
significant success in selling its services to customers, with approximately
86,500 lines sold during 1998. The table below provides selected key operational
data:
 
<TABLE>
<CAPTION>
                                                              AS OF DECEMBER 31,
                                                              -------------------
                                                                 1998        1997
                                                              -----------    ----
<S>                                                           <C>            <C>
Markets Served..............................................            9      0
Number Of Switches Deployed.................................            7      0
Central Office Collocations.................................          101      0
Addressable Market (Business Lines).........................  3.6 million      0
Lines Sold..................................................       86,500     20
Lines Installed.............................................       47,700      9
Sales Force Employees.......................................          295      0
Total Employees.............................................          649     40
</TABLE>
 
     Allegiance does not begin to develop a new market until it has raised the
capital that it projects to be necessary to build its network and operate that
market to the point at which operating cash flow from the market is sufficient
to fund such market's operating costs and capital expenditures.
 
RESULTS OF OPERATIONS
 
     Allegiance commenced operations in August 1997. During the period from
August to December 1997, Allegiance did not sell any services or open any
markets. Instead, substantial effort was devoted to developing business plans,
initiating applications for governmental authorizations, hiring management and
other key personnel, working on the design and development of local exchange
telephone networks and operations support systems, acquiring equipment and
facilities, and negotiating interconnection agreements. Allegiance initiated
service by buying phone lines at wholesale prices and then reselling them to
nine "beta" customers in Dallas during December 1997, generating only $400 of
revenue for that period. Given that Allegiance has significantly increased its
customer base and geographic markets from the commencement of operations in
Dallas during 1997, comparisons of 1998 results with those of 1997 are not
meaningful.
 
     Allegiance first provided service using its own switch and transmission
equipment in April 1998 to customers in New York City. Throughout the remainder
of 1998, it initiated facilities based services in Atlanta, Boston, Chicago,
Dallas, Fort Worth, Los Angeles, Oakland and San Francisco. In January 1999,
Allegiance announced that it was operational in Philadelphia. In March 1999,
Allegiance announced that it was operational in Washington, D.C., including
suburban Maryland and Virginia, and in San Jose. In April 1999, Allegiance
announced that it was operational in Houston. Allegiance plans to open four
additional markets during 1999 for which it has already raised the necessary
capital. With the closing of this offering and of the credit facility, we plan
to accelerate deployment of our networks in Detroit and Baltimore into 1999.
 
     Although Allegiance initiated resale services in Dallas in 1997, Allegiance
sales teams have focused their efforts almost exclusively on selling services
that require the use of Allegiance facilities. Allegiance earns significantly
higher margins by providing facilities based services instead of resale
services. During the fourth quarter of 1998, facilities based lines represented
91% of all lines sold and 83% of all lines installed, as compared to 86% of
lines sold and 73% of lines installed for the third quarter of 1998 and 51% of
lines sold and 17% of lines installed for the second quarter of 1998. For the
full year, 67,100 facilities based lines were sold, and 30,500 of those were
installed. Resale lines sold during 1998 totaled 19,400, of which 17,200 were
installed. Allegiance continues to emphasize the sale of facilities based
services and
 
                                       22
<PAGE>   26
 
lines. We estimate that the proportion of customer lines for which we simply
resell service provided by other carriers will continue to decline to the point
that, eventually, no more than 5% of all lines Allegiance sells will be resale
lines.
 
     During 1998, Allegiance generated $9.8 million of revenue. The majority,
$6.9 million, was local service revenue consisting of:
 
     - the monthly recurring charge for basic service;
 
     - usage based charges for local calls in certain markets;
 
     - charges for services, such as call waiting and call forwarding; and
 
     - to a lesser extent, non-recurring charges, such as charges for additional
       lines for an existing customer.
 
     Access charges, which we earn by connecting Allegiance local service
customers to their selected long distance carriers for outbound calls or by
delivering inbound long distance traffic to Allegiance local service customers,
accounted for $2.2 million of Allegiance's 1998 revenues. Some interexchange
carriers, including AT&T, have also asked the FCC to take regulatory action to
prevent competitive local exchange carriers from charging allegedly "excessive"
access charges. Although no complaints have been filed against us, we do provide
access service to interexchange carriers and we could be subject in the future
to allegations that our charges for this service are unjust and unreasonable.
See "Business -- Regulation -- Federal Regulation." As of December 31, 1998,
approximately 20% of Allegiance's local service customers had chosen Allegiance
as their long distance carrier. Long distance revenues during 1998 amounted to
$.7 million. All other sources of revenue accounted for approximately $10,000
during 1998.
 
     During 1998, Allegiance recognized an insignificant amount of revenue from
"reciprocal compensation" generated by having customers of other local exchange
carriers calling Internet service providers which are Allegiance customers.
Allegiance had no revenue from reciprocal compensation during 1997. Given the
uncertainty as to whether reciprocal compensation should be payable in
connection with calls to Internet service providers, Allegiance recognizes such
revenue only when realization of it is certain, which in most cases will be upon
receipt of cash. See "Business -- Regulation -- Federal Regulation" for a
discussion of reciprocal compensation.
 
     The revenue yield, or revenue generated per line per month, was
approximately $56.00 for all of 1998. Allegiance received significant orders for
lines from certain Internet service providers during the fourth quarter of 1998.
As these lines are installed, the current mix between end-user retail lines and
Internet service provider wholesale lines will change. However, the switch
capacity used for the Internet service provider lines will be well below
Allegiance's policy limit of 20%. Internet service provider wholesale lines
typically generate approximately half the revenue yield, excluding the
reciprocal compensation component of revenue, of that provided by an end-user
retail line. The revenue yield may decline during the first half of 1999 as a
result of the change in the mix. However, data and Internet services such as
frame relay, which is a high speed data service used to transmit data between
computers, dedicated and dial-up access to the Internet, web page design, e-mail
and domain name service, which we introduced in December 1998, may partially, or
perhaps completely, offset the reduction anticipated from the receipt of those
orders.
 
     Although our primary focus is on serving higher margin, higher revenue
generating end-user lines, significant Internet wholesale line orders, such as
those received during the fourth quarter of 1998, contribute positively to gross
margin even excluding the reciprocal compensation component of revenue. For this
reason, we will accept such orders in the future but do not plan to allow the
installation of such lines to constitute more than 20% of our switch capacity.
 
     During 1998, Allegiance did not have sales of or revenue from installation
of customer premise equipment. Allegiance did not have revenue from system
integration activities, wireless, data or Internet
 
                                       23
<PAGE>   27
 
services. Allegiance does not plan to sell customer premise equipment or
wireless services in the foreseeable future.
 
     Acquisitions during 1999 may increase revenues and revenue yield.
Allegiance has had discussions, and will continue to have discussions in the
foreseeable future, concerning potential acquisitions of Internet service
providers and other providers of telecommunications services.
 
     The systems that have historically been used to switch customers from their
existing carrier to Allegiance and to begin providing them service generally
require multiple entries of customer information by hand and exchanged by fax
with the ILEC. In January 1999, Allegiance announced that it had successfully
achieved "electronic bonding" between its operations support systems and those
of Bell Atlantic in the New York City market with respect to processing local
service orders. Electronic bonding is a method in which manual processing and
faxing of information is replaced with electronic processing where our computer
systems and those of other carriers communicate directly. The manual approach
which we must use in the absence of electronic bonding is not only labor
intensive, but also creates numerous opportunities for:
 
     - errors in providing new service and billing;
 
     - service interruptions;
 
     - poor customer service; and
 
     - increased customer turnover.
 
     These problems create added expenses and decrease customer satisfaction.
 
     Without electronic bonding, confirmation of receipt and installation of
orders has taken from two business days to one month. Electronic bonding is
expected to improve productivity by decreasing the period between the time of
sale and the time a customer's line is installed. During 1999, Allegiance
expects to electronically bond with Bell Atlantic in other markets and with
other ILECs. Currently, Allegiance and Bell Atlantic are testing electronic
bonding in Boston and Allegiance and Southwestern Bell are testing electronic
bonding in Dallas. The early results of these efforts have been encouraging.
Allegiance and Pacific Bell are discussing the possibility of using this same
template to pass service requests between these parties. Ameritech has also
contacted us regarding the initiation of a project to electronically bond.
 
     Allegiance is also working towards the electronic bonding of its billing
process, the process of gathering customer specific information about their
current service options and the process of identifying and resolving customer
service problems. These additional "electronic bonding" initiatives will require
additional capital expenditures and should result in additional efficiencies.
 
     Network expenses increased from $.2 million in 1997 to $9.5 million in
1998. This sharp increase is consistent with the deployment of our networks and
initiation and growth of our services during 1998. Network expenses represent:
 
     - the cost of leasing high capacity digital lines that interconnect
       Allegiance's network with ILEC networks;
 
     - the cost of leasing high capacity digital lines that connect Allegiance's
       switching equipment to Allegiance transmission equipment located in ILEC
       central offices;
 
     - the cost of leasing local loop lines which connect Allegiance's customers
       to Allegiance's network;
 
     - the cost of leasing space in ILEC central offices for collocating
       Allegiance transmission equipment; and
 
     - the cost of leasing Allegiance's nationwide Internet network.
 
                                       24
<PAGE>   28
 
     The costs to lease local loop lines and high capacity digital lines from
the ILECs vary by ILEC and are regulated by state authorities under the
Telecommunications Act of 1996. Allegiance believes that in many instances there
are multiple carriers in addition to the ILEC from which it can lease high
capacity lines, and that Allegiance can generally lease those lines at lower
prices than are charged by the ILEC. Allegiance expects that the costs
associated with these leases will increase with customer volume and will be a
significant part of its ongoing cost of services. The cost of leasing switch
sites is also a significant part of Allegiance's ongoing cost of services.
 
     In constructing its initial switching and transmission equipment for a new
market, Allegiance capitalizes only the non-recurring charges associated with
its initial network facilities and the monthly recurring costs of those network
facilities until the switching equipment begins to carry revenue producing
traffic. Typically, the charges for just one to two months are capitalized. We
expense the monthly recurring and non-recurring costs resulting from the growth
of existing collocation sites, and the costs related to expansion of the network
to additional collocation sites in operational markets as we incur these
charges.
 
     In an effort to reduce network expenses, Allegiance is moving to the next
stage of its smart build strategy in New York City and Dallas by entering into
leases for dark fiber to which Allegiance is installing its own electronic
equipment. These leases are accounted for as capital leases. In New York City,
Allegiance has entered into an agreement to lease three rings of dark fiber in
Manhattan with an extension into Brooklyn. In the Dallas market, Allegiance has
reached an agreement to lease one ring of dark fiber in Dallas County.
Allegiance anticipates that any future dark fiber leases will have roughly
similar terms and conditions and therefore it is likely that such additional
dark fiber leases, if any, will also be accounted for as capital leases.
 
     We expect "reciprocal compensation" costs to be a major portion of our cost
of services. Allegiance must enter into an interconnection agreement with the
ILEC in each market to make widespread calling available to Allegiance's
customers. These agreements typically set the cost per minute to be charged by
each party for the calls that are exchanged between the two carriers' networks.
Generally, a carrier must compensate another carrier when a local call by the
first carrier's customer terminates on the second carrier's network. These
reciprocal compensation costs will grow for Allegiance as its customers'
outbound call volume grows. We expect, however, to generate increased revenue
from the ILECs as inbound calling volume to our customers increases. If our
customers' outbound call volume is equivalent to their inbound call volume, our
interconnection costs paid to the ILECs will be substantially offset by the
interconnection revenues we receive from them.
 
     The cost of securing long distance service capacity will increase as
Allegiance's customers long distance calling volume increases. Allegiance
expects that these costs will be a significant portion of its cost of long
distance services. Allegiance has entered into one resale agreement with a long
distance carrier to provide Allegiance with the ability to provide our customers
with long distance service. Allegiance expects to enter into resale agreements
for long distance service with other carriers in the future. Such agreements
typically provide for the resale of long distance services on a per-minute basis
and may contain minimum volume commitments. Allegiance's existing resale
agreement, however, does not contain a minimum volume commitment. If Allegiance
agrees to minimum volume commitments and fails to meet them, it may be obligated
to pay underutilization charges. Under most of these agreements, if a company
underestimates its need for transmission capacity and exceeds the maximum amount
agreed to under such agreements, it may be required to obtain capacity through
more expensive means.
 
     Allegiance leases high capacity digital lines which comprise its Internet
network, and currently has servers in New York, Dallas and San Francisco. The
costs of these lines will increase as Allegiance opens new markets and connects
the additional markets to its Internet network.
 
     Selling, general and administrative expenses increased to $46.1 million in
1998 from just $3.4 million in 1997, primarily due to the growth of our
business. Selling, general and administrative expenses include salaries and
related personnel costs, facilities costs, legal and consulting fees. The number
of employees increased to 649 as of December 31, 1998, from 40 as of December
31, 1997. As of December 31, 1998,
                                       25
<PAGE>   29
 
the sales force, including sales manager and sales administrators, had grown to
295. Allegiance did not employ any account executives, major account managers or
sales engineers prior to January 1998. During 1999, Allegiance expects the
number of its sales personnel to grow significantly. Allegiance currently does
not use agents to sell its services nor does it currently use any print or other
media advertising campaigns. As Allegiance continues to grow in terms of number
of customers and call volume, we expect that ongoing expenses for customer care
and billing will increase.
 
     The magnitude of our net loss for 1998 is principally due to the management
ownership allocation charge, a non-cash charge to income. Allegiance's original
private equity fund investors and its original management team investors owned
95.0% and 5.0%, respectively, of the ownership interests of Allegiance Telecom,
LLC, an entity that owned substantially all of Allegiance's outstanding capital
stock prior to Allegiance's initial public offering of its common stock. As a
result of that offering, the assets of Allegiance Telecom, LLC, which consisted
almost entirely of such capital stock, were distributed to the original fund
investors and management investors in accordance with the Allegiance Telecom,
LLC limited liability company agreement. This agreement provided that the equity
allocation between the fund investors and management investors would be 66.7%
and 33.3%, respectively, based upon the valuation implied by the initial public
offering. Under generally accepted accounting principles, Allegiance recorded
the increase in the assets of Allegiance Telecom, LLC allocated to the
management investors as a $193.5 million increase in additional paid-in capital.
Of this charge, we recorded $122.5 million as a non-cash, non-recurring charge
to operating expense and $71.0 million as a deferred management ownership
allocation charge. We amortized $44.8 million of the deferred charge in 1998. We
will further amortize this deferred charge at $18.8 million, $7.2 million and
$.2 million during 1999, 2000 and 2001, respectively. This period is the
time-frame over which Allegiance has the right to repurchase the securities, at
the lower of fair market value or the price paid by the employee, in the event
the management employee's employment with Allegiance is terminated.
 
     In addition to the above expenses, Allegiance recognized $5.3 million and
$.2 million amortization of deferred stock compensation expense for the years
ended December 31, 1998 and 1997, respectively, also non-cash charges. Such
deferred compensation was recorded in connection with membership units of
Allegiance Telecom, LLC sold to certain management employees and grants to
employees under Allegiance's 1997 Stock Option Plan made prior to Allegiance's
initial public offering of common stock.
 
     Depreciation expense increased from approximately $13,000 in 1997 to $9.0
million in 1998, consistent with the completion of Allegiance's networks and
initiation of services in nine markets by December 31, 1998.
 
     Interest expense for the year ended December 31, 1998 was $39.0 million.
There was no interest expense incurred during 1997. Interest expense recorded
during 1998 reflects the issuance on February 3, 1998 of 11 3/4% Senior Discount
Notes due 2008, and the issuance on July 7, 1998 of 12 7/8% Senior Notes due
2008. See "-- Liquidity and Capital Resources" below for a discussion of these
note offerings. Allegiance capitalizes a portion of its interest costs as part
of the construction cost of its networks, in accordance with Statement of
Financial Accounting Standards No. 34. The amount of interest capitalized during
1998 was $2.8 million. No interest was capitalized during 1997. Interest income
during 1998 and 1997 was $19.9 million and $.1 million, respectively, resulting
from the investment of excess cash and from U.S. Government securities which we
purchased and placed in a pledge account to secure the semi-annual payments of
interest through May 2001 on the 12 7/8% Senior Notes due 2008.
 
     Allegiance has recorded the potential redemption value of its redeemable
warrants in the event that they are redeemed at fair market value in February
2008. Amounts are accreted using the effective interest method and management's
estimates of the future fair market value of such warrants when redemption is
first permitted. Amounts accreted increase the recorded value of such warrants
on the balance sheet and result in a non-cash charge to increase the net loss
applicable to Allegiance's common stock. Accretion of $.5 million related to the
redeemable warrants has been recorded for the year ending December 31, 1998.
 
     Until the consummation of Allegiance's initial public offering of common
stock, Allegiance also recorded the potential redemption values of its
redeemable convertible preferred stock, in the event that
                                       26
<PAGE>   30
 
they would be redeemed at fair market value in August 2004. At the time of the
initial public offering, such preferred stock was converted into common stock.
Accordingly, the amounts accreted for the redeemable convertible preferred stock
were reclassified as an increase to additional paid-in capital in the
stockholders' equity section of the balance sheet, and there has been, and will
be, no additional accretion of redeemable convertible preferred stock values
beyond that point in time. Accretion related to the redeemable convertible
preferred stock of $11.5 million was recorded for the year ending December 31,
1998 and $3.8 million was recorded for the year ending December 31, 1997.
 
     Our net loss for 1998, after the non-cash, one-time management allocation
charge and amortization of deferred compensation and a portion of the deferred
management allocation charge, but before the accretion of the redeemable
convertible preferred stock and redeemable warrants, was $246.5 million and was
$3.7 million for the period from inception to December 31, 1997. After deducting
accretion of preferred stock and warrant values, the net loss applicable to
common stock was $258.5 million and $7.5 million for the year ended December 31,
1998 and for the period from inception to December 31, 1997, respectively.
 
     Many securities analysts use the measure of earnings before deducting
interest, taxes, depreciation and amortization, also commonly referred to as
"EBITDA," as a way of evaluating a company. Allegiance had EBITDA loss of $45.8
million and $3.6 million for the year ended December 31, 1998 and for the period
from inception to December 31, 1997, respectively. In calculating EBITDA,
Allegiance also excludes the non-cash charges to operations for management
ownership allocation charge and deferred stock compensation expense totaling
$172.6 million and $.2 million for the year ended December 31, 1998 and for the
period from inception to December 31, 1997, respectively.
 
     Allegiance expects to continue to experience increasing operating losses
and negative EBITDA as a result of its development activities and as it expands
its operations. Allegiance does not expect to achieve positive EBITDA in any
market until at least its second year of operation in such market.
 
LIQUIDITY AND CAPITAL RESOURCES
 
     Allegiance's financing plan is predicated on the pre-funding of each
market's expansion to positive free cash flow. By using this approach,
Allegiance avoids being in the position of seeking additional capital to fund a
market after Allegiance has already made significant capital investment in that
market. We believe that by raising all required capital prior to making any
commitments in a market, we can raise capital on more favorable terms and
conditions.
 
     Allegiance plans to establish networks in the 24 largest U.S. metropolitan
markets. We estimate that we will need approximately $750 million to $850
million to construct these networks and fund our operating losses in these
markets to the point of positive free cash flow. We have raised approximately
$554 million in total capital since our inception. We believe that the proceeds
from this offering and the borrowings expected to be available under our senior
credit facility, together with existing cash, will be sufficient to fund such
operating and capital requirements in each of our 24 targeted markets.
 
     We may decide to seek additional capital in the future to expand our
business and sources of additional financing may include vendor financing and/or
the private or public sale of Allegiance's equity or debt securities. We cannot
assure you, however, that such financing will be available at all or on terms
acceptable to Allegiance, or that Allegiance's estimate of additional funds
required is accurate.
 
     The actual amount and timing of Allegiance's future capital requirements
may differ materially from its estimates as a result of, among other things:
 
     - the cost of the development of its networks in each of its markets;
 
     - a change in or inaccuracy of its development plans or projections that
       leads to an alteration in the schedule or targets of its roll-out plan;
 
     - the extent of price and service competition for telecommunications
       services in its markets;
 
                                       27
<PAGE>   31
 
     - the demand for its services;
 
     - regulatory and technological developments, including additional market
       developments and new opportunities, in Allegiance's industry;
 
     - an inability to borrow under its senior credit facility; and
 
     - the consummation of acquisitions.
 
     Allegiance's cost of rolling out its networks and operating its business,
as well as its revenues, will depend on a variety of factors, including:
 
     - its ability to meet its roll-out schedules;
 
     - its ability to negotiate favorable prices for purchases of equipment;
 
     - its ability to develop, acquire and integrate the necessary operations
       support systems and other back office systems;
 
     - the number of customers and the services for which they subscribe;
 
     - the nature and penetration of new services that Allegiance may offer; and
 
     - the impact of changes in technology and telecommunication regulations.
 
     As such, actual costs and revenues may vary from expected amounts, possibly
to a material degree, and such variations are likely to affect Allegiance's
future capital requirements.
 
     Allegiance initially raised approximately $50.1 million from certain
members of the Allegiance management team and from affiliates of four private
equity investment funds with extensive experience in financing
telecommunications companies: Madison Dearborn Capital Partners, Morgan Stanley
Capital Partners, Frontenac Company and Battery Ventures.
 
     On February 3, 1998, Allegiance raised gross proceeds of approximately
$250.5 million in an offering of 445,000 units, each unit consisting of one
11 3/4% note and one redeemable warrant. Net proceeds of approximately $240.7
million were received from that offering.
 
     The 11 3/4% notes have a principal amount at maturity of $445.0 million and
an effective interest rate of 12.45%. The 11 3/4% notes mature on February 15,
2008. From and after February 15, 2003, interest on such notes will be payable
semi-annually in cash at the rate of 11 3/4% per annum. The accretion of
original issue discount will cause an increase in indebtedness from December 31,
1998 to February 15, 2008 of $174.5 million.
 
     Allegiance completed the initial public offering of its common stock and
the offering of the 12 7/8% notes early in the third quarter of 1998. Allegiance
raised net proceeds of approximately $124.8 million from the offering of these
notes and approximately $137.8 million from its initial public offering of
common stock.
 
     The 12 7/8% notes mature on May 15, 2008. Interest on these notes is
payable in cash semi-annually, commencing November 15, 1998. The 12 7/8% notes
were sold at less than par, resulting in an effective rate of 13.24%, and the
value of the 12 7/8% notes is being accreted, using the effective interest
method, from the $200.9 million gross proceeds realized at the time of the sale
to the aggregate value at maturity, $205.0 million, over the period ending May
15, 2008. In connection with the sale of the 12 7/8% notes, Allegiance purchased
U.S. Government securities for approximately $69.0 million and placed them in a
pledge account to fund interest payments for the first three years the 12 7/8%
notes are outstanding. The first interest payment was made in November 1998.
Such U.S. Government securities are reflected in the balance sheet as of
December 31, 1998, at an accreted value of approximately $62.2 million, $25.5
million of which we classified as current assets and $36.7 million of which we
classified in other non-current assets.
 
                                       28
<PAGE>   32
 
     Allegiance made capital expenditures of $21.9 million and $113.5 million
during 1997 and 1998, respectively, for property, plant, equipment, software and
hardware necessary in deploying its networks in nine markets and providing
operations and other support systems necessary in conducting its business.
Allegiance also used capital during 1998 to fund its operations; excess cash was
used to purchase short-term investments and money market investments.
 
     On December 31, 1998, Allegiance had transmission equipment collocated in
101 ILEC central offices. Allegiance anticipates that it will more than double
its number of collocations during 1999. As of December 31, 1998, Allegiance had
committed $17.1 million of its capital for switching equipment and switch
facilities and $3.2 million for dark fiber leases. Under Allegiance's current
business plans, it plans to make approximately $250 million in capital
expenditures in 1999, including purchases of switching equipment, switch and
sales facilities, transmission equipment and collocation facilities.
 
     As of December 31, 1998, Allegiance had approximately $405.9 million of
cash and short-term investments. This amount excludes the $62.2 million of
restricted U.S. Government securities that have been placed in a pledge account.
 
     On April 1, 1999, we entered into a credit agreement and related guaranty
agreement with Goldman Sachs Credit Partners L.P., TD Securities (USA) Inc.,
Morgan Stanley Senior Funding, Inc. and various other lenders that provides for
a $225 million senior secured revolving credit facility maturing December 31,
2005 for a subsidiary of Allegiance Telecom, Inc. This revolving facility will
be available, subject to satisfaction of certain terms and conditions, to
provide purchase money financing for the acquisition, construction and
improvement of telecommunications assets by Allegiance's operating subsidiaries.
Borrowings under the facility will not be available until we reach certain
financial and operating objectives, and then will only be available to the
extent we have achieved certain further objectives and have maintained certain
financial ratios and covenants. See the discussion under "Description of Certain
Indebtedness -- Revolving Credit Facility." Based on Allegiance's current
business plan, we do not expect to draw on this facility until 2000.
 
     The facility is structurally senior to Allegiance's 12 7/8% notes and
11 3/4% notes issued in 1998. The facility is secured by substantially all of
the assets of Allegiance's subsidiaries and the stock of the Allegiance
borrowing subsidiary and is guaranteed by Allegiance Telecom, Inc. Interest
rates under the facility are tied to the level of debt compared to consolidated
EBITDA and are initially expected to be the London Interbank Offering Rate +
3.75%. The current commitment fee on the undrawn portion of the facility is
1.50% of the total amount of the facility, with step-downs based on utilization.
The facility also contains certain representations, warranties, covenants and
events of default customary for credits of this nature and otherwise agreed upon
by the parties. See the section titled "Description of Certain
Indebtedness -- Revolving Credit Facility" for a further discussion of this
credit facility.
 
     Allegiance's earnings for the year ended December 31, 1998 and for the
period from inception on April 22, 1997 through December 31, 1997 were
insufficient to cover fixed charges by approximately $249.3 million and $3.7
million, respectively. After giving pro forma effect to the increase in interest
expense resulting from the issuance of the 12 7/8% notes and the 11 3/4% notes
and giving effect to $12.6 million and $171.7 million of management ownership
allocation charge to be recorded in connection with the initial public offering
of common stock, Allegiance's earnings would have been insufficient to cover
fixed charges by approximately $285.1 million and $216.6 million, for the year
ended December 31, 1998 and for the period from inception on April 22, 1997
through December 31, 1997, respectively.
 
IMPACT OF THE YEAR 2000
 
     The "year 2000" issue generally describes the various problems that may
result from the improper processing of dates and date-sensitive transactions by
computers and other equipment as a result of computer hardware and software
using two digits to identify the year in a date. If a computer program or other
piece of equipment fails to properly process dates including and after the year
2000, date-sensitive calculations may be inaccurate. The failure to process
dates could result in network and system failures or
 
                                       29
<PAGE>   33
 
miscalculations causing disruptions in operations including, among other things,
a temporary inability to process transactions, send invoices or engage in other
routine business activities.
 
     State of Readiness. Generally, Allegiance has identified two areas for year
2000 review: internal systems and operations, and external systems and services.
As a new enterprise, Allegiance does not have older systems that are not year
2000 ready. As it develops its network and support systems, Allegiance intends
to ensure that all systems will be year 2000 ready. Allegiance is purchasing its
operations support systems with express specifications, warranties and remedies
that all systems be year 2000 ready. In addition, Allegiance requires all
vendors supplying third party software and hardware to warrant year 2000
readiness. However, there can be no assurance until the year 2000 that all
systems will then function adequately. Also, Allegiance intends to sell its
telecommunications services to companies that may rely upon computerized systems
to make payments for such services, and to interconnect certain portions of its
network and systems with other companies' networks and systems. These
transactions and interactions could expose Allegiance to year 2000 problems.
 
     Allegiance is in the process of conducting a company-wide inventory of all
computer systems on which the company relies, both within and outside of
Allegiance. This inventory is scheduled to be completed by the end of May 1999.
Allegiance will use this inventory to contact its external suppliers, vendors
and providers to obtain information about their year 2000 readiness and, based
on that information, will assess the extent to which these external information
technology and non-information technology systems, including embedded
technology, could cause a material adverse effect on Allegiance's operations in
the event that the systems fail to properly process date-sensitive transactions
after December 31, 1999.
 
     Allegiance's assessment of its year 2000 readiness will be ongoing as it
continues to develop its own operations support systems and becomes reliant on
the systems of additional third parties as a result of the geographic expansion
of its business into additional markets. As a result, Allegiance may in the
future identify a significant internal or external year 2000 issue which, if not
remedied in a timely manner, could have a material adverse effect on
Allegiance's business, financial condition and results of operations.
 
     Costs to Address Year 2000 Issues. Allegiance has used its internal
information technology and other personnel, in identifying year 2000 issues.
Allegiance does not anticipate any significant costs to make its internal
systems year 2000 compliant because it does not expect any remediation to be
required and does not expect to make material expenditures for outside
consultants to assist Allegiance in its effort to address year 2000 issues.
Because no material year 2000 issues have yet been identified in connection with
external sources, Allegiance cannot reasonably estimate costs that may be
required for remediation or for implementation of contingency plans. As
Allegiance gathers information relating to external sources of year 2000 issues,
Allegiance will reevaluate its ability to estimate costs associated with year
2000 issues. There can be no assurance that as additional year 2000 issues are
addressed, Allegiance's costs to remediate such issues will be consistent with
its historical costs.
 
     Risks of Year 2000 Issues. Allegiance cannot reasonably ascertain the
extent of the risks involved in the event that any one system fails to process
date-sensitive calculations accurately because it has not identified any
material year 2000 issues. Potential risks include:
 
     - the inability to process customer billing accurately or in a timely
       manner;
 
     - the inability to provide accurate financial reporting to management,
       auditors, investors and others;
 
     - litigation costs associated with potential suits from customers and
       investors;
 
     - delays in implementing other information technology projects as a result
       of work by internal personnel on year 2000 issues;
 
     - delays in receiving payment or equipment from customers or suppliers as a
       result of their systems' failure; and
 
     - the inability to occupy and operate in a facility.
 
                                       30
<PAGE>   34
 
     Any one of these risks, if they materialize, could individually have a
material adverse effect on Allegiance's business, financial condition or results
of operations.
 
     All of Allegiance's information technology and non-information technology
systems and products relating to Allegiance's external issues are manufactured
or supplied by other companies outside of Allegiance's control. As a result, we
cannot assure you that the systems of any of those companies will be year 2000
ready. In particular, Allegiance will be dependent upon other ILECs, long
distance carriers and other companies for interconnection and completion of
off-network calls. These interconnection arrangements are material to
Allegiance's ability to conduct its business and failure by any of these
providers to be year 2000 ready may have a material adverse effect on
Allegiance's business in the affected market. Moreover, although Allegiance has
taken every precaution to purchase its internal systems to be fully year 2000
ready, there can be no assurance that every vendor will fully comply with the
contract requirements. If some or all of Allegiance's internal and external
systems fail or are not year 2000 ready in a timely manner, there could be a
material adverse effect on Allegiance's business, financial condition or results
of operations.
 
     Contingency Plans. Even though Allegiance has not identified any specific
year 2000 issues, Allegiance believes that the design of its networks and
support systems could provide Allegiance with certain operating contingencies in
the event material external systems fail. In all of its markets, however,
Allegiance has or intends to establish interconnection agreements with the ILECs
and other regional and international carriers. If one of these carriers fails
for any reason, including year 2000 problems, there may be little Allegiance can
do to mitigate the impact of such a failure on Allegiance's operations.
Allegiance has attempted to ensure that its own operating facilities and systems
are fully backed up with auxiliary power generators capable of operating all
equipment and systems for indeterminate periods should power supplies fail,
subject to the availability of fuel to run these generators. Allegiance also has
the ability to relocate headquarters and administrative personnel to other
Allegiance facilities should power and other services at its Dallas headquarters
fail. Because of the inability of Allegiance's contingency plans to eliminate
the negative impact that disruptions in ILEC service or the service of other
carriers would create, there can be no assurance that Allegiance will not
experience numerous disruptions that could have a material effect on
Allegiance's operations.
 
QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK
 
     Allegiance's investment policy is limited by its existing bond indentures.
Allegiance is restricted to investing in financial instruments with a maturity
of one year or less. The indentures require investments in high quality
instruments, such as obligations of the U.S. Government or any agency thereof
guaranteed by the United States of America, money market deposits, and
commercial paper with a rating of A1/P1.
 
     Allegiance is thus exposed to market risk related to changes in short-term
interest rates. Allegiance manages these risks by closely monitoring market
rates and the duration of its investments. Allegiance does not enter into
financial or commodity investments for speculation or trading purposes and is
not a party to any financial or commodity derivatives.
 
                                       31
<PAGE>   35
 
     Interest income earned on Allegiance's investment portfolio is affected by
changes in short-term U.S. interest rates. Allegiance believes that it is not
exposed to significant changes in fair value because of its conservative
investment strategy. However, the estimated interest income for the calendar
year 1999, based on the average 1998 earned rate on investments, is $13.6
million and assuming a 100 basis point drop in the average rate, Allegiance
would be exposed to a $2.5 million reduction in interest income for the year.
The following table illustrates this impact on a quarterly basis:
 
<TABLE>
<CAPTION>
                                                                              QUARTER ENDING
                                                              ----------------------------------------------
                                                              MARCH     JUNE    SEPTEMBER   DECEMBER
                                                               1999     1999      1999        1999     TOTAL
                                                              ------   ------   ---------   --------   -----
                                                                             ($S IN MILLIONS)
<S>                                                           <C>      <C>      <C>         <C>        <C>
Estimated Average Outstanding Balance.......................  $367.4   $290.7    $213.9      $131.8
Estimated Interest Earned at Estimated Rate of 5.4% at
  December 31, 1998.........................................  $ 5.0    $  3.9    $  2.9      $  1.8    $13.6
Estimated Impact of Interest Rate drop......................  $ 0.9    $  0.7    $  0.6      $  0.3    $ 2.5
</TABLE>
 
     Allegiance has outstanding long term, fixed rate notes, not subject to
interest rate fluctuations.
 
                                       32
<PAGE>   36
 
                                    BUSINESS
 
OVERVIEW
 
     Allegiance seeks to be a premier provider of telecommunications services to
business, government and other institutional users in 24 of the largest major
metropolitan areas across the United States. Allegiance offers an integrated set
of telecommunications products and services including local exchange, local
access, domestic and international long distance, enhanced voice, data and a
full suite of Internet services. Allegiance generally prices these services at a
discount of 5% to 15% below the prices charged by the incumbent local exchange
carriers. Allegiance was founded in April 1997 by a management team led by Royce
J. Holland, the former President, Chief Operating Officer and co-founder of MFS
Communications, and Thomas M. Lord, former Managing Director of Bear, Stearns &
Co. Inc., where he specialized in the telecommunications, information services
and technology industries.
 
     Allegiance believes that the Telecommunications Act, by opening the local
exchange market to competition, has created an attractive opportunity for new
facilities-based competitive local exchange carriers like Allegiance. Most
importantly, the Telecommunications Act stated that these carriers, known as
CLECs, should be able to lease the various elements of the ILECs' networks,
which are necessary for the cost-effective provision of service. This aspect of
the Telecommunications Act, which is referred to as "unbundling" the ILEC
networks, has enabled Allegiance to deploy digital switches with local and long
distance capability and lease fiber optic lines from the ILECs, other CLECs, and
other telecommunications companies to connect Allegiance's switch with its
transmission equipment located in ILEC central offices. Once traffic volume
growth justifies further capital investment, Allegiance may lease dark fiber or
construct its own fiber network.
 
     Allegiance has developed procedures, together with its back office systems
vendors, MetaSolv, DSET, Lucent and Intertech, that it believes will provide it
with a significant competitive advantage in terms of reducing costs, processing
large order volumes and providing customer service. Back office systems enable a
phone company to enter, schedule and track a customer's order from the point of
sale to the installation and testing of service. These systems also include or
interface with trouble management, inventory, billing, collection and customer
service systems.
 
     Allegiance is determined to achieve electronic bonding, the on-line and
real-time connection of Allegiance's operations support systems with those of
the ILECs, with each of the incumbent telecommunications companies in most of
its markets by the end of 1999. On January 8, 1999, Allegiance and Bell Atlantic
became the first facilities-based CLEC and ILEC to formally engage in electronic
bonding after working since April 1998 to develop the necessary software and
processes. This will allow Allegiance to create service requests on-line,
leading to faster installations of customer orders through a reduction in errors
associated with multiple manual inputs. Allegiance expects electronic bonding to
improve productivity by decreasing the period between the time of sale and the
time a customer's line is installed in the Allegiance network. In addition,
Allegiance expects that the simplified process will reduce selling, general and
administrative costs.
 
     Allegiance believes that it will be some time before many other CLECs and
telecommunications service companies will be able to implement similar
electronic bonding systems. Unlike Allegiance, which is a new company designing
its systems specifically for electronic bonding, most of these other carriers
have systems that have been in place for years and already support a large
number of customers with ongoing service. Updating these systems can therefore
disrupt service and be much more costly and time consuming.
 
     Allegiance intends to continue network deployment of its initial 24
markets. Allegiance estimates that these 24 markets will include more than 21
million non-residential access lines. According to Allegiance estimates, this
represents approximately 44.7% of the total non-residential access lines in the
U.S. With a strategy focusing on the central business districts and suburban
commercial districts in these areas, Allegiance plans to address a majority of
the non-residential access lines in most of its targeted markets.
 
                                       33
<PAGE>   37
 
     As of April 14, 1999, Allegiance was operational in thirteen markets: New
York City, Dallas, Atlanta, Fort Worth, Chicago, Los Angeles, San Francisco,
Boston, Oakland, Philadelphia, Washington, D.C., San Jose and Houston. As of
such date, Allegiance was in the process of deploying networks in four other
markets: Long Island, Northern New Jersey, Orange County and San Diego.
 
BUSINESS STRATEGY
 
     To accomplish its goal of becoming a premier provider of telecommunications
services to business, government, and other institutional users in major U.S.
metropolitan areas, Allegiance has developed a customer-focused business
strategy designed to achieve significant market penetration and deliver superior
customer care while maximizing operating margins. The key components of this
strategy include the following:
 
     Leverage Proven Management Team. Allegiance's veteran management team has
extensive experience and past successes in the CLEC industry. Allegiance
believes that its ability to combine and draw upon the collective talent and
expertise of its senior management gives it a competitive advantage in the
effective and efficient execution of network deployment, sales, provisioning,
service installation, billing and collection, and customer service functions.
Allegiance's Chairman and Chief Executive Officer, Royce J. Holland, has more
than 25 years of experience in the telecommunications and energy industries,
including as President, Chief Operating Officer and co-founder of MFS
Communications, one of the first companies to compete with the ILECs. Under his
leadership, MFS Communications grew from a start-up operation to become the
largest competitor to the incumbent local exchange carriers. It grew to $1.1
billion in revenues before its acquisition by WorldCom, Inc. in 1996. Dan Yost,
the President and Chief Operating Officer of Allegiance, has more than 26 years
of telecommunications industry experience, including experience as President and
Chief Operating Officer of Netcom On-Line Communications Services, Inc. from
July 1997 to February 1998, and as President, Southwest Region of AT&T Wireless
Services, Inc. from June 1994 to July 1997. Other key Allegiance executives have
significant experience in the critical functions of network operations, sales
and marketing, back office and operations support systems, finance and
regulatory affairs.
 
     Target Customers with Integrated Service Offerings. Allegiance focuses
principally on customers in the business, government and other institutional
market segments. The majority of our customers are small and medium-sized
businesses, to which we offer "one-stop shopping" by giving them the ability to
purchase a comprehensive package of communications services from a single
supplier. We also offer convenient integrated billing and a single point of
contact for sales and service. We offer the following services in most of our
markets:
 
     - local and long distance services,
 
     - local area network interconnection,
 
     - frame relay, a high speed data service used to transmit data between
       computers and designed to operate at higher speeds,
 
     - Internet services, and
 
     - Integrated Services Digital Network ("ISDN"), an internationally agreed
       upon standard which, through special equipment, allows two-way,
       simultaneous voice and data transmission in digital formats over the same
       transmission line.
 
     In addition, we expect to offer the following services beginning in 1999:
 
     - Digital Subscriber Lines ("DSL"), which allow high speed digital
       connection for carrying voice and data traffic over copper lines,
 
     - Web page design, and
 
     - Web server hosting.
 
                                       34
<PAGE>   38
 
     These comprehensive services are generally not available from the ILECs, or
available only at high prices. By offering a comprehensive package of
communications services together with traditional local and long distance
services, we believe that we can accelerate our ability to establish new
customer accounts and reduce the number of customers who discontinue our
services and switch to other telecommunications providers.
 
     For large businesses and government and other institutional users, which
typically obtain telecommunications services from a variety of suppliers, we
focus primarily on capturing a significant portion of these customers' local
exchange, intraLATA toll, which are the calls that fall within a local service
area, and data traffic. Although we will principally target end-users in markets
where we believe we can achieve significant market penetration by providing
superior customer care at competitive prices, we may augment our core business
strategy by selectively supplying wholesale services including equipment
collocation and facilities management services to Internet service providers.
 
     Utilize "Smart Build" Strategy to Maximize Speed to Market and Minimize
Investment Risk. We will continue to pursue what we refer to as a "smart build"
strategy. Under this strategy, we
 
     - purchase and install switches;
 
     - locate our equipment in the central office facilities of incumbent local
       exchange carriers; and
 
     - lease unbundled network elements from the incumbent local exchange
       carriers until growth justifies our ownership of additional network
       assets.
 
     Once traffic volume justifies further investment, we may then lease dark
fiber or construct our own fiber network.
 
     We believe that this smart build strategy offers a number of economic
benefits. First, the strategy allows us to enter into a new market in a six- to
nine-month time frame, less than half the 18-24 months generally required under
the traditional "build first, sell later" approach required before the
Telecommunications Act established a framework for CLECs to acquire unbundled
network elements. We believe that this smart build strategy has the additional
advantage of reducing initial capital requirements in each market, allowing us
to focus our initial capital resources on the critical areas of sales, marketing
and operations support systems, instead of on constructing extensive fiber optic
networks to each customer.
 
     We are currently implementing this smart build strategy in all of our
networks where we lease high capacity circuits to connect the central office
facilities of incumbent local exchange carriers with our switches. In New York
City, we are moving to the next stage of our smart build strategy, by leasing a
thirty-mile dark fiber ring in Manhattan which extends into Brooklyn. We are in
the process of leasing a dark fiber ring in the Dallas market.
 
     Achieve Broad Coverage of Attractive Areas within Each Targeted Market. As
a result of the substantial up-front capital requirements necessary to construct
metropolitan area fiber networks, CLECs have traditionally limited their initial
networks to highly concentrated downtown areas, which limits their ability to
provide service to customers in other attractive, but geographically dispersed,
markets. We prepare a detailed, "bottoms-up" analysis of a market's local
exchange areas using FCC and demographic data. We use this analysis, together
with estimates of the costs and potential benefits of addressing particular
service areas to:
 
     - identify attractive markets;
 
     - determine the optimal concentration of areas to be served; and
 
     - develop our schedule for deploying and expanding our network.
 
     This will enable us to address the most attractive service areas throughout
each of our target markets, such as suburban business parks and concentrated
downtown areas, without having to construct our own fiber network to the
customer premises in each of these areas.
 
                                       35
<PAGE>   39
 
     Maximize Operating Margins by Emphasizing Facilities-Based Services. We
believe that by using our own facilities to provide local exchange, local
access, and long distance service, we should generate significantly higher gross
margins than we could obtain by reselling services provided entirely on another
carrier's facilities. As a result, we focus our marketing activities on areas
where we can serve customers through a direct connection using unbundled loops
or high capacity circuits connected to our facilities. We generally resell ILEC
services only to provide comprehensive geographical service coverage to
customers with multiple sites where the customer is physically connected to our
switches and which can be addressed by our facilities-based services, and a few
off-switch sites, which can be addressed only by reselling ILEC services.
 
     Build Market Share by Focusing on Direct Sales. We use a direct sales force
to sell directly to customers and provide them personalized customer care
through a single point of contact. By using this approach, we hope to maximize
our market share, particularly among small and medium-sized businesses. We
believe that ILECs have generally neglected to target small and medium-sized
business customers with direct sales efforts. Our sales management team is
composed of executives with experience in managing a large number of direct
sales specialists in the telecommunications and data networking industries.
Additionally, we believe that we can attract and retain highly qualified sales
and support personnel by offering them the opportunity to:
 
     - work with an experienced and success-proven management team in building a
       developing, entrepreneurial company;
 
     - market a comprehensive set of products and services and customer care
       options; and
 
     - participate in the potential economic returns made available through a
       results-oriented compensation package emphasizing sales commissions and
       stock options.
 
     Develop Efficient Automated Back Office Systems. We intend to automate most
of the processes involved in switching a customer to our networks. Our goal is
to accelerate the time between customer order and service installation, reduce
overhead costs and improve customer service. To achieve this goal, we are
developing, acquiring and integrating information technology systems to support
our operations, and we are establishing an electronic bonding arrangement with
the incumbent local exchange carriers. To address these critical issues, we have
hired an experienced team of engineering and information technology
professionals. This team is working to develop, with the assistance of key third
party vendors, operations support systems that synchronize multiple tasks such
as provisioning, customer service and billing and provide management with timely
operating and financial data to most efficiently direct network, sales and
customer service resources. In addition, with electronic bonding, we should be
able to provide better customer care since we will be able to more readily
pinpoint any problems with a customer's order. See "-- Information Systems" for
a discussion of electronic bonding.
 
     Expand Through Potential Acquisitions. We plan to pursue strategic
acquisitions to accelerate our market penetration, expand our customer base, and
acquire additional experienced management.
 
                                       36
<PAGE>   40
 
MARKET OPPORTUNITY
 
     U.S. Census Bureau data indicates that the United States communications
services market, including cable television, but excluding Internet access and
content, in 1997 totaled approximately $256 billion in annual revenue. As
depicted on the chart below, wireline telecommunications services, other than
Internet access and content, purchased by non-residential users accounted for
about 44%, or approximately $113 billion, of the total U.S. market in 1997:
                        [US COMMUNICATIONS MARKET GRAPH]
 
     The major segments of the non-residential wireline telecommunications
services market, based on U.S. Census Bureau data, are as follows:
           [NON-RESIDENTIAL WIRELINE TELECOMMUNICATIONS MARKET GRAPH]
 
     Traditional voice traffic accounted for the vast majority of
non-residential communications revenue in 1997, with local exchange and exchange
access accounting for over half of the total non-residential wireline
telecommunications market, excluding Internet access and content. Due to its
rapid growth, estimates of data and Internet services revenue are not as well
established as those relating to traditional voice traffic communications.
However, Allegiance believes that a significant market opportunity exists for
providers of non-residential Internet services.
 
     Allegiance believes that the rapid opening of the local market to
competition, accelerated growth rates in local traffic related to increases in
Internet access, the desire for multiple suppliers by large businesses, and the
desire for "one-stop shopping" by small and medium-sized businesses and
consumers, presents an opportunity for new entrants to achieve product
differentiation and significant penetration into this very large, established
market. Success in this environment will, in the opinion of management, depend
 
                                       37
<PAGE>   41
 
primarily on speed-to-market, marketing creativity, superior customer service,
and a CLEC's ability to provide competitively priced services rapidly and
accurately and to issue concise, accurate integrated billing statements.
 
ALLEGIANCE'S TELECOMMUNICATIONS SERVICES
 
     Allegiance tailors its service offerings to meet the specific needs of the
business, government, and other institutional customers in its target markets.
Management believes that Allegiance's close contact with customers from its
direct sales force and customer care personnel will enable it to tailor its
service offerings to meet customers' needs and to creatively package its
services to provide "one-stop shopping" solutions for those customers.
 
     Local Exchange Services. Allegiance offers local telephone services,
including local dial tone as well as other features such as:
 
     - call forwarding;
 
     - call waiting;
 
     - dial back;
 
     - caller ID; and
 
     - voice mail.
 
     By offering dial tone service, Allegiance also receives originating and
terminating access charges for interexchange calls placed or received by its
subscribers.
 
     Private Branch Exchange/Shared Tenant Services. In areas where telephone
density is high and most telephone customers desire similar services, such as
office buildings, apartments, condominiums or campus-type environments, a
private branch exchange or services such as Centrex are among the most efficient
means of providing telephone services. A private branch exchange, also known as
"PBX," is a switching system located within an office building and owned by a
customer which allows calls from the outside to be routed directly to the
individual instead of through a central number. PBX also allows for calling
within an office by way of four digit extensions. Centrex is a service that
offers features similar to those of a PBX, except that the switching equipment
is located at the telephone carrier's premises and not at the customer's
premises. The use of the Centrex service eliminates the need for large capital
expenditures on a PBX. Allegiance intends to offer these services in areas where
market potential warrants.
 
     Integrated Services Digital Network and High Speed Data
Services. Allegiance offers high speed data transmission services, such as:
 
     - wide area network interconnection, which are remote computer
       communications systems that allow file sharing among geographically
       distributed workgroups; wide area networks typically use links provided
       by local telephone companies; and
 
     - broadband Internet access, also known as "wideband," which allows large
       quantities of data to be transmitted simultaneously.
 
     These services may be provided via frame relay and dedicated point-to-point
connections. In order to provide these services, Allegiance intends to utilize
leased high capacity connections, such as multiple DS-1, DS-3, T1 or T3
connections, to medium- and large-sized business, government and other
institutional customers. Allegiance may also employ DSL and/or ISDN connections
over unbundled copper wire connections to smaller business users whose
telecommunications requirements may not justify such high capacity connections
or which are located in areas where T1 connections are not available.
 
     Interexchange/Long Distance Services. Allegiance offers a full range of:
 
     - domestic long distance services, such as:
 
      -- interLATA, which are calls that pass one "Local Access and Transport
         Area" or "LATA" to another, and such calls must be carried across the
         LATA boundary by a long-distance carrier,
 
                                       38
<PAGE>   42
 
      -- intraLATA, which is a call that falls within the local service area of
         a single local telephone company, and
 
     - international long distance services.
 
     These services include "1+" outbound calling, inbound toll free service,
and such complementary services as calling cards, operator assistance, and
conference calling.
 
     Enhanced Internet Services. Allegiance offers dedicated and dial-up high
speed Internet access services via conventional modem connections, ISDN, and T1
and higher speed dedicated connections. In addition, Allegiance expects to offer
DSL services beginning in 1999. Dedicated access services are telecommunications
lines dedicated or reserved for use by particular customers.
 
     Web Site Design and Hosting Services. Allegiance plans to offer Web site
design services and Web site hosting on its own computer servers to provide
customers with a complete, easy to use key solution that gives them a presence
on the World Wide Web.
 
     Facilities and Systems Integration Services. Allegiance offers individual
customers assistance with the:
 
     - design and implementation of complete, easy to use solutions in order to
       meet their specific needs, including the selection of the customer's
       premises equipment, interconnection of local area networks and wide area
       networks, and
 
     - implementation of virtual private networks. Virtual private networks
       simulate private line networks without actually building a private
       network and offer special services such as abbreviated dialing, where a
       customer can call between offices in different area codes without having
       to dial all eleven digits.
 
     Wholesale Services to Internet Service Providers. Allegiance believes that
with the recent growth in demand for Internet services, numerous Internet
service providers are unable to obtain network capacity rapidly enough to meet
customer demand and eliminate network congestion problems. Allegiance plans to
supplement its core customer product offerings by providing a full array of
local services to Internet service providers, including telephone numbers and
switched and dedicated access to the Internet.
 
SALES AND CUSTOMER SUPPORT
 
     Allegiance offers an integrated package of local exchange, local access,
domestic and international long distance, enhanced voice, data, and a full suite
of Internet services to small and medium-sized businesses. Unlike large
corporate, government, or other institutional users, small and medium-sized
businesses often have no in-house telecommunications manager. Based on
management's previous experience, Allegiance believes that a direct sales and
customer care program focusing on complete, "one-stop shopping" solutions will
have a competitive advantage in capturing this type of customer's total
telecommunications traffic.
 
     Although the vast majority of Allegiance's sales force is focused primarily
on the small and medium-sized business segment, Allegiance also provides
services to large business, government, and other institutional users, as well
as to Internet service providers, and expects that a significant portion of its
initial revenue will come from these segments. Therefore, Allegiance has
organized its sales and customer care organizations to serve each of these three
market segments. Sales and marketing approaches in the telecommunications market
are market-segment specific, and Allegiance believes the following are the most
effective approaches with respect to its three targeted market segments:
 
     - Small/medium businesses -- Allegiance uses direct sales.
 
     - Large business, government, and other institutional users -- Allegiance
       uses account teams, established business relationships, applications
       sales and technical journal articles, and is an exhibitor at trade shows.
 
                                       39
<PAGE>   43
 
     - Wholesale carriers, primarily Internet service providers -- Allegiance
       uses direct sales, established business relationships, and competitive
       pricing.
 
     Allegiance organizes account executives into teams of six to eight persons
with a team manager and a sales support specialist. These teams utilize
telemarketing to "qualify" leads and set up initial appointments. Allegiance
closely manages account executives with regard to the number of sales calls per
week, with the goal of eventually calling on every prospective business customer
in an account executive's sales territory. Allegiance uses commission plans and
incentive programs to reward and retain the top performers and encourage strong
customer relationships. The sales team managers for each market report to a city
sales vice president who in turn reports to a regional vice president.
 
     Allegiance's wholesale sales to Internet service providers are performed by
account executives reporting to the vice president of national accounts. The
vice president of national accounts also has responsibility for large corporate,
government, and other institutional accounts, with designated national account
managers and sales support personnel assigned to the major accounts. Unlike the
small and medium-sized business segment, the national account program is being
built by recruiting national account managers with established business
relationships with large corporate accounts, supported by technical applications
personnel and customer care specialists.
 
     Allegiance has focused its efforts on developing a personalized customer
care program. Allegiance's customer service representatives are available seven
days a week, 24 hours a day. In addition, Allegiance uses customer care
specialists to support its national accounts.
 
INFORMATION SYSTEMS
 
     Allegiance is continuing to develop its tailored information systems and
procedures for operations support and other back office systems that it believes
will provide a significant competitive advantage in terms of cost, processing
large order volumes, and customer service. These systems are required to enter,
schedule, provision, and track a customer's order from the point of sale to the
installation and testing of service and also include or interface with trouble
management, inventory, billing, collection and customer service systems. The
existing systems currently employed by most ILECs, CLECs and long distance
carriers, which were developed prior to the passage of the Telecommunications
Act, generally require multiple entries of customer information to accomplish
order management, provisioning, switch administration and billing. This process
is not only labor intensive, but it creates numerous opportunities for errors in
provisioning service and billing, delays in installing orders, service
interruptions, poor customer service, increased customer turnover, and
significant added expenses due to duplicated efforts and decreased customer
satisfaction.
 
     Allegiance believes that the practical problems and costs of upgrading
existing systems are often prohibitive for companies whose existing systems
support a large number of customers with ongoing service. Because Allegiance
does not have systems designed prior to the expanded interaction between CLECs
and ILECs introduced by the Telecommunications Act, Allegiance's team of
engineering and information technology professionals experienced in the CLEC
industry is free to develop operations support and other back office systems
designed to facilitate a smooth, efficient order management, provisioning,
trouble management, billing and collection, and customer care process. See "Risk
Factors -- We Are Dependent on Effective Billing, Customer Service and
Information Systems and We May Have Difficulties in Developing These Systems."
 
     Order Management. Allegiance is licensing MetaSolv's order management
software. This product allows the sales team not only to enter customer orders
onsite, via computer and/or over the Internet, but also to monitor the status of
the order as it progresses through the service initiation process.
 
     Provisioning Management. The licensed order management software also
supports the design and management of the provisioning process, including
circuit design and work flow management. The system has been designed to permit
programming into the system of a standard schedule of tasks which must be
accomplished in order to initiate service to a customer, as well as the standard
time intervals during which
                                       40
<PAGE>   44
 
each such task must be completed. This way, when a standard order is selected in
the system, each required task in the service initiation process can be
efficiently managed to its assigned time interval.
 
     External Interfaces. Several external interfaces are required to initiate
service for a customer. While some of these are automated via gateways from the
order management software, the most important interfaces, those to the ILEC,
have generally been accomplished via fax or e-mail. In an effort to make this
process more efficient, Allegiance and Bell Atlantic announced on January 8,
1999, the first implementation of electronic bonding between the operations
support system of a facilities-based CLEC and an ILEC.
 
     Electronic bonding will allow Allegiance to access data from the ILEC,
submit service requests electronically, and more quickly attend to errors in the
local service request form because an order is bounced back immediately if the
ILEC determines that there is a mistake. As a result, Allegiance expects to be
able to eventually reduce the time frame required to switch service to
Allegiance from approximately 25 business days to as low as five business days,
as compared to three days currently required to switch to a new long distance
carrier. Electronic bonding should also enable Allegiance to improve its ability
to provide better customer care since Allegiance will more readily be able to
pinpoint where any problems may have occurred with a customer's order.
 
     Network Element Administration. Allegiance licenses their software for
administrating each element of the Allegiance network. Allegiance is currently
developing an interface between its order management system and the network
element manager to integrate data integrity and eliminate redundant data entry.
 
     Customer Billing. Allegiance has selected a billing services provider which
credits the collections made to Allegiance's lock-box. Customer information is
electronically interfaced with this provider from Allegiance's order management
system via a gateway, thereby integrating all repositories of information. We
are continuing to develop other enhancements to the gateway.
 
     Billing Records. Local and intraLATA billing records are generated by the
Lucent Series 5ESS(R)-2000 switches to record customer calling activity.
InterLATA billing records are generated by the long distance carrier with whom
Allegiance has a resale agreement, to record customer calling activity. These
records will be automatically processed by the billing services provider in
order to calculate and produce bills in a customer-specified billing format.
 
NETWORK DEPLOYMENT
 
     As of April 14, 1999, Allegiance was operational in thirteen markets: New
York City, Dallas, Atlanta, Fort Worth, Chicago, Los Angeles, San Francisco,
Boston, Oakland, Philadelphia, Washington, D.C., San Jose and Houston. As of
such date, Allegiance was in the process of deploying networks in four other
markets: Long Island, Northern New Jersey, Orange County and San Diego.
 
                                       41
<PAGE>   45
 
     The following table sets forth the initial markets targeted by Allegiance
and the current buildout schedule. The order and timing of network deployment
may vary and will depend on a number of factors, including recruiting city
management, the regulatory environment, Allegiance's results of operations and
the existence of specific market opportunities, such as acquisitions. Allegiance
may also elect not to deploy networks in each such market.
 
                       MARKET SIZE AND BUILDOUT SCHEDULE
 
<TABLE>
<CAPTION>
                                              ESTIMATED TOTAL        % OF TOTAL            INITIAL
                                              NON-RESIDENTIAL   U.S. NON-RESIDENTIAL   FACILITIES-BASED
MARKET                                        ACCESS LINES(1)     ACCESS LINES(2)      SERVICE DATE(3)
- ------                                        ---------------   --------------------   ----------------
                                                (THOUSANDS)
<S>                                           <C>               <C>                    <C>
New York City...............................       3,298(4)              6.7%(4)       March 1998
Dallas, TX..................................         867(5)              1.8%(5)       April 1998
Atlanta, GA.................................         612                 1.2%          April 1998
Fort Worth, TX..............................          --(5)               --(5)        July 1998
Chicago, IL.................................       1,951                 4.0%          September 1998
Los Angeles, CA.............................       3,430(6)              7.0%(6)       October 1998
San Francisco, CA...........................       2,148(7)              4.4%(7)       November 1998
Boston, MA..................................         649                 1.3%          December 1998
Oakland, CA.................................          --(7)               --(7)        December 1998
Philadelphia, PA............................       1,754                 3.6%          February 1999
Washington, D.C. ...........................         871                 1.8%          March 1999
San Jose, CA................................          --(7)               --(7)        March 1999
Houston, TX.................................         765                 1.6%          April 1999
Northern New Jersey.........................          --(4)               --(4)        1999
Orange County, CA...........................          --(6)               --(6)        1999
San Diego, CA...............................         790                 1.6%          1999
Long Island, NY.............................          --(4)               --(4)        1999
Baltimore, MD...............................         639                 1.3%          1999
Detroit, MI.................................         821                 1.7%          1999
Denver, CO..................................         632                 1.3%          2000
Seattle, WA.................................         779                 1.6%          2000
Cleveland, OH...............................         654                 1.3%          2000
Miami, FL...................................         769                 1.6%          2000
St. Louis, MO...............................         449                 0.9%          2000
                                                  ------                ----
          Total.............................      21,878                44.7%
                                                  ======                ====
</TABLE>
 
- ---------------
 
(1) Data as of December 31, 1996.
 
(2) Based on an estimated 49.0 million U.S. non-residential access lines as of
    December 31, 1996.
 
(3) Refers to the first month during which Allegiance could offer
    facilities-based service or the year during which Allegiance expects to be
    able to offer facilities-based service based on its current business plan.
 
(4) Data for New York City also includes Northern New Jersey and Long Island,
    NY.
 
(5) Data for Dallas, TX also includes Fort Worth, TX.
 
(6) Data for Los Angeles, CA also includes Orange County, CA.
 
(7) Data for San Francisco, CA also includes San Jose, CA and Oakland, CA.
 
     In the majority of its targeted markets, Allegiance will initially deploy
switches and collocate transmission equipment in ILEC central offices with heavy
concentrations of non-residential access lines. Over time, Allegiance plans to
expand its networks throughout the metropolitan areas to address the majority of
the business market in each area. In some markets, such as Northern New Jersey,
Allegiance
 
                                       42
<PAGE>   46
 
will not initially deploy its own switch, but will deploy transmission equipment
in major central offices and route traffic to an existing Allegiance switch
until traffic growth warrants the addition of a switch to service that market.
 
NETWORK ARCHITECTURE
 
     An important element of Allegiance's smart build strategy is the
installation of Lucent Series 5ESS(R)-2000 digital switches and related
equipment at a central location in each market. As of April 14, 1999, Allegiance
had deployed nine switches to serve thirteen markets: New York City, Dallas,
Atlanta, Chicago, Los Angeles, San Francisco, Fort Worth, Oakland, Boston,
Philadelphia, Washington, D.C., San Jose and Houston. As of such date,
Allegiance was installing an additional switch in San Diego.
 
     Initially, Allegiance intends to lease local network trunking facilities
from the ILEC and/or one or more CLECs in order to connect Allegiance's switch
to major ILEC central offices serving the central business district and outlying
areas of business concentrations in each market. The switch will also be
connected to ILEC tandem switches and certain interexchange carrier
points-of-presence, the equivalent of a local phone company's central office. To
access the largest number of customers possible without having to lay fiber to
each of their premises, Allegiance will also locate access equipment such as
integrated digital loop carriers and related equipment in each of the ILEC
central offices in which it is connected.
 
     As each customer is signed up, service will be provided by leasing
unbundled loops from the ILEC to connect Allegiance's integrated digital loop
carriers located in the serving central office to the customer premise
equipment. For large business, government, or other institutional customers or
for numerous customers located in large buildings, it may be more cost-effective
for Allegiance to use leased ILEC or CLEC capacity in the 1.5 to 150 megabit
range, or perhaps a wireless local loop leased from one of the emerging wireless
CLECs, to connect the customer(s) to the Allegiance network. In this case,
Allegiance will locate its integrated digital loop carriers or other equipment
in the customer's building.
 
     Although Allegiance will initially lease its local network transmission
facilities, Allegiance plans to replace leased capacity with its own fiber optic
facilities as and when it experiences sufficient traffic volume growth between
its switch and specific ILEC central offices or as other factors make these
arrangements more attractive.
 
IMPLEMENTATION OF SERVICES
 
     To offer services in a market, Allegiance generally must secure
certification from the state regulator and typically must file tariffs or price
lists for the services that it will offer. The certification process varies from
state to state; however, the fundamental requirements are largely the same.
State regulators require new entrants to demonstrate that they have secured
adequate financial resources to establish and maintain good customer service.
New entrants must also show that they possess the knowledge and ability required
to establish and operate a telecommunications network. Allegiance has made such
demonstrations in Texas, Georgia, California, Illinois, Maryland, New York, New
Jersey, Virginia, Massachusetts, Washington, D.C., Colorado, Michigan and
Washington, where Allegiance has obtained certificates to provide local exchange
and intrastate toll services. An application for such authority is pending in
Pennsylvania, where Allegiance has obtained interim operating authority.
Allegiance intends to file similar applications in the near future in Ohio,
Missouri and Florida.
 
     Before providing local service, a new entrant must negotiate and execute an
interconnection agreement with the ILEC. While such agreements can be voluminous
and may take months to negotiate, most of the key interconnection issues have
now been thoroughly addressed and commissions in most states have ruled on
arbitrations between the ILECs and new entrants. However, interconnection rates
and conditions may be subject to change as the result of future commission
actions or other changes in the regulatory environment. Under a recent United
States Supreme Court ruling, new entrants may adopt either all or portions of an
interconnection agreement already entered into by the ILEC and another carrier.
Such an approach will be selectively adopted by Allegiance to enable it to enter
markets quickly while at the same time preserving its right to replace the
adopted agreement with a customized interconnection agreement
                                       43
<PAGE>   47
 
that can be negotiated once service has already been established. For example,
Allegiance has adopted the interconnection agreement entered into between
Southwestern Bell and WinStar Wireless of Texas, Inc. in Texas and has begun to
negotiate enhancements to that agreement for ultimate inclusion in Allegiance's
customized agreement with Southwestern Bell.
 
     While such interconnection agreements include key terms and prices for
interconnection, a significant joint implementation effort must be made with the
ILEC in order to establish operationally efficient and reliable traffic
interchange arrangements. Such interchange arrangements must include those
between the new entrant's network and the facilities of other service providers
as well as public service agencies. For example, Allegiance worked closely with
Southwestern Bell in order to devise and implement an efficient 911 call routing
plan that will meet the requirements of each individual 911 service bureau in
Southwestern Bell areas that Allegiance will serve using its own switches.
Allegiance meets with key personnel from 911 service bureaus to obtain their
acceptance and to establish dates for circuit establishment and joint testing.
Other examples of traffic interchange and interconnection arrangements utilizing
the ILEC's network include connectivity to its out-of-band signaling facilities,
interconnectivity to the ILEC's operator services and directory assistance
personnel, and access through the ILEC to the networks of wireless companies and
interexchange carriers.
 
     Allegiance has entered into interconnection agreements with the ILECs in
each of the states in which its current eleven geographic markets are located.
In Georgia, New York and Texas, however, the original interconnection agreements
have expired. Allegiance is operating under the terms of these agreements while
negotiating new interconnection agreements. The new agreements will likely have
retroactive effective dates.
 
     After the initial implementation activities are completed in a market,
Allegiance follows an on-going capacity management plan to ensure that adequate
quantities of network facilities, such as interconnection trunks are in place,
and a contingency plan must be devised to address spikes in demand caused by
events such as a larger-than-expected customer sale in a relatively small
geographic area.
 
REGULATION
 
     Allegiance's telecommunications services business is subject to federal,
state and local regulation.
 
  Federal Regulation
 
     The FCC regulates interstate and international telecommunications services,
including the use of local telephone facilities to originate and terminate
interstate and international calls. Allegiance provides such services on a
common carrier basis. The FCC imposes certain regulations on common carriers
such as the ILECs that have some degree of market power. The FCC imposes less
regulation on common carriers without market power including, to date, CLECs
like Allegiance. The FCC requires common carriers to receive an authorization to
construct and operate telecommunications facilities, and to provide or resell
telecommunications services, between the United States and international points.
 
     Under the Telecommunications Act, any entity, including cable television
companies and electric and gas utilities, may enter any telecommunications
market, subject to reasonable state regulation of safety, quality and consumer
protection. Because implementation of the Telecommunications Act is subject to
numerous federal and state policy rulemaking proceedings and judicial review
there is still uncertainty as to what impact such legislation will have on
Allegiance.
 
     The Telecommunications Act is intended to increase competition. The act
opens the local services market by requiring ILECs to permit interconnection to
their networks and establishing ILEC obligations with respect to:
 
          Reciprocal Compensation. Requires all local exchange carriers to
     complete calls originated by competing local exchange carriers under
     reciprocal arrangements at prices based on tariffs or negotiated prices.
 
                                       44
<PAGE>   48
 
          Resale. Requires all ILECs and CLECs to permit resale of their
     telecommunications services without unreasonable restrictions or
     conditions. In addition, ILECs are required to offer wholesale versions of
     all retail services to other telecommunications carriers for resale at
     discounted rates, based on the costs avoided by the ILEC in the wholesale
     offering.
 
          Interconnection. Requires all ILECs and CLECs to permit their
     competitors to interconnect with their facilities. Requires all ILECs to
     permit interconnection at any technically feasible point within their
     networks, on nondiscriminatory terms, at prices based on cost, which may
     include a reasonable profit. At the option of the carrier seeking
     interconnection, collocation of the requesting carrier's equipment in the
     ILECs' premises must be offered, except where an ILEC can demonstrate space
     limitations or other technical impediments to collocation.
 
          Unbundled Access. Requires all ILECs to provide nondiscriminatory
     access to unbundled network elements including, network facilities,
     equipment, features, functions, and capabilities, at any technically
     feasible point within their networks, on nondiscriminatory terms, at prices
     based on cost, which may include a reasonable profit.
 
          Number Portability. Requires all ILECs and CLECs to permit users of
     telecommunications services to retain existing telephone numbers without
     impairment of quality, reliability or convenience when switching from one
     telecommunications carrier to another.
 
          Dialing Parity. Requires all ILECs and CLECs to provide "1+" equal
     access to competing providers of telephone exchange service and toll
     service, and to provide nondiscriminatory access to telephone numbers,
     operator services, directory assistance, and directory listing, with no
     unreasonable dialing delays.
 
          Access to Rights-of-Way. Requires all ILECs and CLECs to permit
     competing carriers access to poles, ducts, conduits and rights-of-way at
     regulated prices.
 
     ILECs are required to negotiate in good faith with carriers requesting any
or all of the above arrangements. If the negotiating carriers cannot reach
agreement within a prescribed time, either carrier may request binding
arbitration of the disputed issues by the state regulatory commission. Where an
agreement has not been reached, ILECs remain subject to interconnection
obligations established by the FCC and state telecommunication regulatory
commissions.
 
     In August 1996, the FCC released a decision establishing rules implementing
the ILEC interconnection obligations described above. On July 18, 1997, the
Eighth Circuit vacated certain portions of this decision and narrowly
interpreted the FCC's power to prescribe and enforce rules implementing the
Telecommunications Act. On January 25, 1999, the United States Supreme Court
reversed the Eighth Circuit decision and reaffirmed the FCC's broad authority to
issue rules implementing the Telecommunications Act, although it did vacate a
rule determining which network elements the incumbent local exchange carriers
must provide to competitors on an unbundled basis. Allegiance, however, leases
only the basic unbundled network elements from the ILEC and therefore does not
expect reconsideration of the unbundling rules to have an adverse effect on its
smart build strategy.
 
     Nevertheless, the FCC likely will conduct additional rulemaking proceedings
to conform to the Supreme Court's interpretation of the law, and these
proceedings may result in further judicial review. While these court proceedings
were pending, Allegiance entered into interconnection agreements with a number
of ILECs through negotiations or, in some cases, adoption of another CLEC's
approved agreement. These agreements remain in effect, although in some cases
one or both parties may be entitled to demand renegotiation of particular
provisions based on intervening changes in the law. However, it is uncertain
whether Allegiance will be able to obtain renewal of these agreements on
favorable terms when they expire.
 
     The Telecommunications Act codifies the ILECs' equal access and
nondiscrimination obligations and preempts inconsistent state regulation. The
Telecommunications Act also contains special provisions that replace prior
antitrust restrictions that prohibited the regional Bell operating companies
from providing
                                       45
<PAGE>   49
 
long distance services and engaging in telecommunications equipment
manufacturing. The Telecommunications Act permitted the regional Bell operating
companies to enter the out-of-region long distance market immediately upon its
enactment. Further, provisions of the Telecommunications Act permit a regional
Bell operating company to enter the long distance market in its in-region states
if it satisfies several procedural and substantive requirements, including:
 
     - obtaining FCC approval upon a showing that the regional Bell operating
       company has entered into interconnection agreements or, under some
       circumstances, has offered to enter into such agreements in those states
       in which it seeks long distance relief;
 
     - the interconnection agreements satisfy a 14-point "checklist" of
       competitive requirements; and
 
     - the FCC is satisfied that the regional Bell operating company's entry
       into long distance markets is in the public interest.
 
     To date, several petitions by regional Bell operating companies for such
entry have been denied by the FCC, and none have been granted. However, it is
likely that additional petitions will be filed in 1999 and it is possible that
regional Bell operating companies may receive approval to offer long distance
services in one or more states. This may have an unfavorable effect on
Allegiance's business. Allegiance is legally able to offer its customers both
long distance and local exchange services, which the regional Bell operating
companies currently may not do. This ability to offer "one-stop shopping" gives
Allegiance a marketing advantage that it would no longer enjoy. See
"-- Competition."
 
     On May 8, 1997, the FCC released an order establishing a significantly
expanded federal universal service subsidy regime. For example, the FCC
established new subsidies for telecommunications and information services
provided to qualifying schools and libraries with an annual cap of $2.25 billion
and for services provided to rural health care providers with an annual cap of
$400 million. The FCC also expanded the federal subsidies for local exchange
telephone services provided to low-income consumers. Providers of interstate
telecommunications service, such as Allegiance must pay for a portion of these
programs. Allegiance's share of these federal subsidy funds will be based on its
share of certain defined telecommunications end user revenues. Currently, the
FCC is assessing such payments on the basis of a provider's revenue for the
previous year. The FCC announced that it intends, effective July 1, 1999, to
revise its rules for subsidizing service provided to consumers in high cost
areas, which may result in further substantial increases in the overall cost of
the subsidy program. Several parties have appealed the May 8th order. Such
appeals have been consolidated and transferred to the United States Court of
Appeals for the Fifth Circuit where they are currently pending.
 
     For the first half of 1999, Allegiance expects to incur a contribution
liability equal to approximately 1.5% of its 1998 operating revenues. With
respect to subsequent periods, however, Allegiance is currently unable to
quantify the amount of subsidy payments that it will be required to make or the
effect that these required payments will have on its financial condition.
 
     Under authority granted by the FCC, Allegiance will resell the
international telecommunications services of other common carriers between the
United States and international points. In connection with such authority,
Allegiance's subsidiary, Allegiance Telecom International, Inc., has filed
tariffs with the FCC stating the rates, terms and conditions for its
international services.
 
     With respect to its domestic service offerings, various subsidiaries of
Allegiance have filed tariffs with the FCC stating the rates, terms and
conditions for their interstate services. Allegiance's tariffs are generally not
subject to pre-effective review by the FCC, and can be amended on one day's
notice. Allegiance's interstate services are provided in competition with
interexchange carriers and, with respect to access services, the ILECs. With
limited exceptions, the current policy of the FCC for most interstate access
services dictates that ILECs charge all customers the same price for the same
service. Thus, the ILECs generally cannot lower prices to those customers likely
to contract for their services without also lowering charges for the same
service to all customers in the same geographic area, including those whose
telecommunications requirements would not justify the use of such lower prices.
The FCC may, however,
 
                                       46
<PAGE>   50
 
alleviate this constraint on the ILECs and permit them to offer special rate
packages to very large customers, as it has done in a few cases, or permit other
forms of rate flexibility. The FCC has adopted some proposals that significantly
lessen the regulation of ILECs that are subject to competition in their service
areas and provide such ILECs with additional flexibility in pricing their
interstate switched and special access on a central office specific basis; and,
as discussed in the following paragraph, is considering expanding such
flexibility.
 
     In two orders released on December 24, 1996, and May 16, 1997, the FCC made
major changes in the interstate access charge structure. In the December 24th
order, the FCC removed restrictions on ILECs' ability to lower access prices and
relaxed the regulation of new switched access services in those markets where
there are other providers of access services. If this increased pricing
flexibility is not effectively monitored by federal regulators, it could have a
material adverse effect on Allegiance's ability to compete in providing
interstate access services. The May 16th order substantially increased the costs
that ILECs subject to the FCC's price cap rules recover through monthly,
non-traffic sensitive access charges and substantially decreased the costs that
these carriers recover through traffic sensitive access charges. In the May 16th
order, the FCC also announced its plan to bring interstate access rate levels
more in line with cost. The plan will include rules that may grant these
carriers increased pricing flexibility upon demonstrations of increased
competition or potential competition in relevant markets. The manner in which
the FCC implements this approach to lowering access charge levels could have a
material effect on Allegiance's ability to compete in providing interstate
access services. Several parties appealed the May 16th order. On August 19,
1998, the May 16th order was affirmed by the Eighth Circuit U.S. Court of
Appeals. The FCC is now considering public comments on pricing flexibility
proposals submitted by two regional Bell operating companies and on changing the
productivity factor (currently 6.5%), which is applied annually to reduce ILECs'
price cap indices.
 
     ILECs around the country have been contesting whether the obligation to pay
reciprocal compensation to competitive local exchange carriers should apply to
local telephone calls from an ILEC's customers to Internet service providers
served by competitive local exchange carriers. The ILECs claim that this traffic
is interstate in nature and therefore should be exempt from compensation
arrangements applicable to local, intrastate calls. Competitive local exchange
carriers have contended that the interconnection agreements provide no exception
for local calls to Internet service providers and reciprocal compensation is
therefore applicable. Currently, over 25 state commissions and several federal
and state courts have ruled that reciprocal compensation arrangements do apply
to calls to Internet service providers, and no jurisdiction has ruled to the
contrary. Certain of these rulings are subject to appeal. Additional disputes
over the appropriate treatment of Internet service provider traffic are pending
in other states.
 
     On February 26, 1999, the FCC released a Declaratory Ruling determining
that Internet service provider traffic is interstate for jurisdictional
purposes, but that its current rules neither require nor prohibit the payment of
reciprocal compensation for such calls. In the absence of a federal rule, the
FCC determined that state commissions have authority to interpret and enforce
the reciprocal compensation provisions of existing interconnection agreements,
and to determine the appropriate treatment of Internet service provider traffic
in arbitrating new agreements. The FCC also requested comment on alternative
federal rules to govern compensation for such calls in the future. In response
to the FCC ruling, some regional Bell operating companies have asked state
commissions to reopen previous decisions requiring the payment of reciprocal
compensation on Internet service provider calls.
 
     Allegiance anticipates that Internet service providers will be among its
target customers, and adverse decisions in state proceedings could limit its
ability to service this group of customers profitably. Allegiance limits the
switch capacity used for Internet service provider lines to 20%. In addition,
given the uncertainty as to whether reciprocal compensation should be payable in
connection with calls to Internet service providers, Allegiance recognizes such
revenue only when realization of it is certain, which in most cases will be upon
receipt of cash.
 
                                       47
<PAGE>   51
 
  State Regulation
 
     The Telecommunications Act is intended to increase competition in the
telecommunications industry, especially in the local exchange market. With
respect to local services, ILECs are required to allow interconnection to their
networks and to provide unbundled access to network facilities, as well as a
number of other procompetitive measures. Because the implementation of the
Telecommunications Act is subject to numerous state rulemaking proceedings on
these issues, it is currently difficult to predict how quickly full competition
for local services, including local dial tone, will be introduced.
 
     State regulatory agencies have regulatory jurisdiction when Allegiance
facilities and services are used to provide intrastate services. A portion of
Allegiance's current traffic may be classified as intrastate and therefore
subject to state regulation. Allegiance expects that it will offer more
intrastate services, including intrastate switched services, as its business and
product lines expand and state regulations are modified to allow increased local
services competition. To provide intrastate services, Allegiance generally must
obtain a certificate of public convenience and necessity from the state
regulatory agency and comply with state requirements for telecommunications
utilities, including state tariffing requirements.
 
     State agencies, like the FCC, require Allegiance to file periodic reports,
pay various fees and assessments, and comply with rules governing quality of
service, consumer protection, and similar issues. Although the specific
requirements vary from state to state, they tend to be more detailed than the
FCC's regulation because of the strong public interest in the quality of basic
local exchange service. Allegiance intends to comply with all applicable state
regulations, and as a general matter does not expect that these requirements of
industry-wide applicability will have a material adverse effect on its business.
However, no assurance can be given that the imposition of new regulatory burdens
in a particular state will not affect the profitability of Allegiance's services
in that state.
 
  Local Regulation
 
     Allegiance's networks are subject to numerous local regulations such as
building codes and licensing. Such regulations vary on a city by city and county
by county basis. If Allegiance decides in the future to install its own fiber
optic transmission facilities, it will need to obtain rights-of-way over private
and publicly owned land. There can be no assurance that such rights-of-way will
be available to Allegiance on economically reasonable or advantageous terms.
 
COMPETITION
 
     The telecommunications industry is highly competitive. Allegiance believes
that the principal competitive factors affecting its business will be pricing
levels and clear pricing policies, customer service, accurate billing and, to a
lesser extent, variety of services. The ability of Allegiance to compete
effectively will depend upon its continued ability to maintain high quality,
market-driven services at prices generally equal to or below those charged by
its competitors. To maintain its competitive posture, Allegiance believes that
it must be in a position to reduce its prices in order to meet reductions in
rates, if any, by others. Any such reductions could adversely affect Allegiance.
Many of Allegiance's current and potential competitors have financial, personnel
and other resources, including brand name recognition, substantially greater
than those of Allegiance, as well as other competitive advantages over
Allegiance.
 
     Local Exchange Carriers. In each of the markets targeted by Allegiance,
Allegiance will compete principally with the ILEC serving that area, such as
Ameritech, BellSouth, Southwestern Bell, Bell Atlantic or US WEST. Allegiance
believes the regional Bell operating companies' primary agenda is to be able to
offer long distance service in their service territories. The independent
telephone companies have already achieved this goal with good early returns.
Many experts expect the regional Bell operating companies to be successful in
entering the long distance market in a few states sometime in 1999. Allegiance
believes the regional Bell operating companies expect to offset share losses in
their local markets by capturing a significant percentage of the in-region long
distance market, especially in the residential segment where the regional Bell
operating companies' strong regional brand names and extensive advertising
campaigns may be very successful. See "-- Regulation."
                                       48
<PAGE>   52
 
     As a recent entrant in the integrated telecommunications services industry,
Allegiance has not achieved and does not expect to achieve a significant market
share for any of its services. In particular, the ILECs have long-standing
relationships with their customers, have financial, technical and marketing
resources substantially greater than those of Allegiance, have the potential to
subsidize competitive services with revenues from a variety of businesses and
currently benefit from certain existing regulations that favor the ILECs over
Allegiance in certain respects. While recent regulatory initiatives, which allow
CLECs such as Allegiance to interconnect with ILEC facilities, provide increased
business opportunities for Allegiance, such interconnection opportunities have
been and likely will continue to be accompanied by increased pricing flexibility
for and relaxation of regulatory oversight of the ILECs.
 
     ILECs have long-standing relationships with regulatory authorities at the
federal and state levels. While recent FCC administrative decisions and
initiatives provide increased business opportunities to telecommunications
providers such as Allegiance, they also provide the ILECs with increased pricing
flexibility for their private line and special access and switched access
services. In addition, with respect to competitive access services as opposed to
switched access services, the FCC recently proposed a rule that would provide
for increased ILEC pricing flexibility and deregulation for such access services
either automatically or after certain competitive levels are reached. If the
ILECs are allowed by regulators to offer discounts to large customers through
contract tariffs, engage in aggressive volume and term discount pricing
practices for their customers, and/or seek to charge competitors excessive fees
for interconnection to their networks, the income of competitors to the ILECs,
including Allegiance, could be materially adversely affected. If future
regulatory decisions afford the ILECs increased access services pricing
flexibility or other regulatory relief, such decisions could also have a
material adverse effect on competitors to the ILEC, including Allegiance.
 
     Competitive Access Carriers/Competitive Local Exchange
Carriers/Interexchange Carriers/ Other Market Entrants. Allegiance also faces,
and expects to continue to face, competition from other current and potential
market entrants, including long distance carriers seeking to enter, reenter or
expand entry into the local exchange market such as AT&T, MCI WorldCom, and
Sprint, and from other CLECs, resellers of local exchange services, competitive
access providers, cable television companies, electric utilities, microwave
carriers, wireless telephone system operators and private networks built by
large end users. In addition, a continuing trend toward consolidation of
telecommunications companies and the formation of strategic alliances within the
telecommunications industry, as well as the development of new technologies,
could give rise to significant new competitors to Allegiance. For example,
WorldCom acquired MFS Communications in December 1996, acquired another CLEC,
Brooks Fiber Properties, Inc. in 1997, and recently merged with MCI. AT&T
recently acquired Teleport Communications Group Inc., a CLEC, and
TeleCommunications, Inc., a cable, telecommunications and high-speed Internet
services provider. Ameritech Corporation has agreed to merge with SBC
Communications; and Bell Atlantic has agreed to merge with GTE Corporation.
These types of consolidations and strategic alliances could put Allegiance at a
competitive disadvantage.
 
     The Telecommunications Act includes provisions which impose certain
regulatory requirements on all local exchange carriers, including competitors
such as Allegiance, while granting the FCC expanded authority to reduce the
level of regulation applicable to any or all telecommunications carriers,
including ILECs. The manner in which these provisions of the Telecommunications
Act are implemented and enforced could have a material adverse effect on
Allegiance's ability to successfully compete against ILECs and other
telecommunications service providers. Allegiance also competes with equipment
vendors and installers, and telecommunications management companies with respect
to certain portions of its business.
 
     The changes in the Telecommunications Act radically altered the market
opportunity for traditional competitive access providers and CLECs. Due to the
fact that most existing competitive access providers/ CLECs initially entered
the market providing dedicated access in the pre-1996 era, these companies had
to build a fiber infrastructure before offering services. Switches were added by
most competitive access providers/CLECs in the last year to take advantage of
the opening of the local market. With the Telecommunications Act requiring
unbundling of the local exchange carrier networks, competitive access
                                       49
<PAGE>   53
 
providers/CLECs will now be able to more rapidly enter the market by installing
switches and leasing trunk and loop capacity until traffic volume justifies
building facilities. New CLECs will not have to replicate existing facilities
and can be more opportunistic in designing and implementing networks.
 
     A number of CLECs have entered or announced their intention to enter into
one or more of the same markets as Allegiance. Allegiance believes that not all
CLECs however, are pursuing the same target customers as Allegiance.
Demographically, business customers are divided into three segments: small,
medium and large. Targeted cities are divided into three segments by population:
Tier 1, Tier 2 and Tier 3. As would be expected, each CLEC may focus on
different combinations of primary and secondary target customers.
 
     Allegiance has chosen to focus primarily on small and medium-sized business
customers in large "Tier 1" markets. To help distinguish itself from other
competitors who have adopted a similar strategy, Allegiance uses a direct sales
approach to offer potential customers "one-stop shopping" services through a
single point of contact. In addition, Allegiance is actively pursuing
collocations throughout all of its target markets which, in combination with its
smart build strategy, is expected to allow Allegiance to access its markets and
provide a greater array of services more quickly than if it were able to use a
traditional build approach.
 
     Allegiance believes the major interexchange carriers, such as AT&T, MCI
WorldCom and Sprint, have a two pronged strategy:
 
     - keep the regional Bell operating companies out of in-region long distance
       as long as possible, and
 
     - develop facilities-based and unbundled local service, an approach already
       being pursued by MCI WorldCom with the acquisition of MFS Communications,
       and more recently by AT&T with its acquisitions of Teleport
       Communications and TeleCommunications, Inc.
 
     Competition for Provision of Long Distance Services. The long distance
telecommunications industry has numerous entities competing for the same
customers and a high average turnover rate, as customers frequently change long
distance providers in response to the offering of lower rates or promotional
incentives by competitors. Prices in the long distance market have declined
significantly in recent years and are expected to continue to decline.
Allegiance expects to increasingly face competition from companies offering long
distance data and voice services over the Internet. Such companies could enjoy a
significant cost advantage because they do not currently pay carrier access
charges or universal service fees.
 
     Data/Internet Service Providers. The Internet services market is highly
competitive, and Allegiance expects that competition will continue to intensify.
Allegiance's competitors in this market will include Internet service providers,
other telecommunications companies, online services providers and Internet
software providers. Many of these competitors have greater financial,
technological and marketing resources than those available to Allegiance.
 
     Competition from International Telecommunications Providers. Under the
recent World Trade Organization agreement on basic telecommunications services,
the United States and 72 other members of the World Trade Organization committed
themselves to opening their respective telecommunications markets and/or foreign
ownership and/or to adopting regulatory measures to protect competitors against
anticompetitive behavior by dominant telecommunications companies, effective in
some cases as early as January 1998. Although Allegiance believes that this
agreement could provide Allegiance with significant opportunities to compete in
markets that were not previously accessible and to provide more reliable
services at lower costs than Allegiance could have provided prior to
implementation of this agreement, it could also provide similar opportunities to
Allegiance's competitors and facilitate entry by foreign carriers into the U.S.
market. There can be no assurance that the pro-competitive effects of the World
Trade Organization agreement will not have a material adverse effect on
Allegiance's business, financial condition and results of operations or that
members of the World Trade Organization will implement the terms of this
agreement.
 
                                       50
<PAGE>   54
 
EMPLOYEES
 
     As of December 31, 1998, Allegiance had approximately 649 full-time
employees. Allegiance believes that its future success will depend on its
continued ability to attract and retain highly skilled and qualified employees.
None of Allegiance's employees are currently represented by a collective
bargaining agreement. Allegiance believes that it enjoys good relationships with
its employees.
 
LEGAL PROCEEDINGS
 
     On August 29, 1997, WorldCom sued Allegiance and two of its Senior Vice
Presidents. In its complaint, WorldCom alleges that these employees violated
noncompete and nonsolicitation agreements by accepting employment with
Allegiance and by soliciting then-current WorldCom employees to leave WorldCom's
employment and join Allegiance. In addition, WorldCom claims that Allegiance
tortiously interfered with WorldCom's relationships with its employees, and that
Allegiance's behavior constituted unfair competition. WorldCom seeks injunctive
relief, including barring two of Allegiance's executives from continued
employment with Allegiance, and monetary damages, although it has filed no
motion for a temporary restraining order or preliminary injunction. Allegiance
denies all claims and is vigorously defending itself. Allegiance does not expect
the ultimate outcome of this matter to have a material adverse effect on the
results of operations or financial condition of Allegiance.
 
     On October 7, 1997, Allegiance filed a counterclaim against WorldCom for,
among other things, attempted monopolization of the "one-stop shopping"
telecommunications market, abuse of process, and unfair competition. WorldCom
did not move to dismiss the attempted monopolization claim, but moved to dismiss
the abuse of process and unfair competition claims. On March 4, 1998, the court
dismissed the claim for unfair competition.
 
     Allegiance is not party to any other pending legal proceedings that
Allegiance believes would, individually or in the aggregate, have a material
adverse effect on Allegiance's financial condition or results of operations.
 
FACILITIES
 
     Allegiance is headquartered in Dallas, Texas and leases offices and space
in a number of locations, primarily for sales offices and network equipment
installations. The table below lists Allegiance's current leased facilities:
 
<TABLE>
<CAPTION>
                                                                            APPROXIMATE
LOCATION                                                LEASE EXPIRATION   SQUARE FOOTAGE
- --------                                                ----------------   --------------
<S>                                                     <C>                <C>
Dallas, TX............................................  February 2008          76,000
Atlanta, GA...........................................  February 2003           7,400
Atlanta, GA...........................................  November 2001           7,300
Boston, MA............................................  September 2003         12,000
Boston, MA............................................  September 2008         18,000
Chicago, IL...........................................  March 2009             11,000
Chicago, IL...........................................  July 2008              14,000
Fort Worth, TX........................................  June 2003               3,900
Houston, TX...........................................  December 2005          11,700
Houston, TX...........................................  November 2008          18,000
Los Angeles, CA.......................................  June 2008              11,700
Los Angeles, CA.......................................  June 2008              14,585
Newport, CA...........................................  April 2006              7,800
New York, NY..........................................  August 2006             8,700
New York, NY..........................................  March 2008             19,500
New York, NY..........................................  June 2008              12,400
Oakland, CA...........................................  December 2006           2,000
</TABLE>
 
                                       51
<PAGE>   55
 
<TABLE>
<CAPTION>
                                                                            APPROXIMATE
LOCATION                                                LEASE EXPIRATION   SQUARE FOOTAGE
- --------                                                ----------------   --------------
<S>                                                     <C>                <C>
Philadelphia, PA......................................  April 2002              8,900
Philadelphia, PA......................................  October 2008           18,000
San Diego, CA.........................................  March 2008             14,000
San Francisco, CA.....................................  April 2002              8,100
San Francisco, CA.....................................  June 2008              16,000
San Jose, CA..........................................  February 2004           4,500
Washington, DC........................................  November 2008          15,000
Washington, DC........................................  November 2006           8,200
Westchester, IL.......................................  January 2001           10,700
Westchester, IL.......................................  April 2001              5,700
</TABLE>
 
     Allegiance believes that its leased facilities are adequate to meet its
current needs in the markets in which it has begun to deploy networks, and that
additional facilities are available to meet its development and expansion needs
in existing and projected target markets for the foreseeable future.
 
                                       52
<PAGE>   56
 
                                   MANAGEMENT
 
DIRECTORS, EXECUTIVE OFFICERS AND OTHER KEY EMPLOYEES
 
     The following table sets forth information concerning the directors,
executive officers and other key personnel of Allegiance, including their ages
as of December 31, 1998:
 
<TABLE>
<CAPTION>
NAME                                   AGE                     POSITION(S)
- ----                                   ---                     -----------
<S>                                    <C>   <C>
Royce J. Holland.....................  50    Chairman of the Board and Chief Executive
                                             Officer
C. Daniel Yost.......................  50    President and Chief Operating Officer and
                                             Director
Thomas M. Lord.......................  42    Executive Vice President of Corporate
                                             Development, Chief Financial Officer and
                                               Director
John J. Callahan.....................  49    Senior Vice President of Sales and Marketing
                                             and Director
Dana A. Crowne.......................  38    Senior Vice President and Chief Engineer
Stephen N. Holland...................  47    Senior Vice President and Chief Information
                                             Officer
Patricia E. Koide....................  50    Senior Vice President of Human Resources, Real
                                               Estate, Training Facilities and
                                               Administration
Gregg A. Long........................  45    Senior Vice President of Development and
                                             Regulatory
Mark B. Tresnowski...................  39    Senior Vice President, General Counsel and
                                             Secretary
Anthony J. Parella...................  39    National Vice President of Field Sales
Paul D. Carbery......................  37    Director
James E. Crawford, III...............  53    Director
John B. Ehrenkranz...................  33    Director
Paul J. Finnegan.....................  46    Director
Richard D. Frisbie...................  49    Director
Alan E. Goldberg.....................  44    Director
Reed E. Hundt........................  51    Director
James N. Perry, Jr...................  38    Director
</TABLE>
 
     Royce J. Holland, Allegiance's Chairman of the Board and Chief Executive
Officer, has more than 25 years of experience in the telecommunications,
independent power and engineering/construction industries. Prior to founding
Allegiance in April 1997, Mr. Holland was one of several co-founders of MFS
Communications, where he served as President and Chief Operating Officer from
April 1990 until September 1996 and as Vice Chairman from September 1996 to
February 1997. In January 1993, Mr. Holland was appointed by President George
Bush to the National Security Telecommunications Advisory Committee. Mr. Holland
was recently named Chairman of the Association for Local Telecommunications
Services, the industry trade organization for the competitive local telephone
sector. Mr. Holland also presently serves on the board of directors of CSG
Systems, a publicly held billing services company. Mr. Holland's brother,
Stephen N. Holland, is employed as Allegiance's Senior Vice President and Chief
Information Officer.
 
     C. Daniel Yost, who joined Allegiance as President and Chief Operating
Officer in February 1998, was elected to Allegiance's board of directors in
March 1998. Mr. Yost has more than 26 years of experience in the
telecommunications industry. From July 1997 until he joined Allegiance, Mr. Yost
was the President and Chief Operating Officer for U.S. Operations of Netcom
On-Line Communications Services, Inc., a leading Internet service provider. Mr.
Yost served as the President, Southwest Region of AT&T Wireless Services, Inc.
from June 1994 to July 1997. Prior to that, from July 1991 to June 1994, Mr.
Yost was the President, Southwest Region of McCaw Cellular Communications/LIN
Broadcasting.
 
                                       53
<PAGE>   57
 
     Thomas M. Lord, a co-founder and director of Allegiance and its Executive
Vice President of Corporate Development and Chief Financial Officer, is
responsible for overseeing Allegiance's mergers and acquisitions, corporate
finance and investor relations functions. Mr. Lord is an 18-year veteran in
investment banking, securities research and portfolio management, including
serving as a managing director of Bear, Stearns & Co. Inc. from January 1986 to
December 1996. In the five-year period ending December 1996, Mr. Lord oversaw 43
different transactions valued in excess of $6.2 billion for the
telecommunications, information services and technology industries.
 
     John J. Callahan, who joined Allegiance as Senior Vice President of Sales
and Marketing in December 1997, has more than 18 years of experience in the
telecommunications industry. Most recently, Mr. Callahan was President of the
Western Division for MFS Communications from December 1991 to November 1997,
where he was responsible for the company's sales and operations in Arizona,
California, Georgia, Florida, Illinois, Michigan, Missouri, Ohio, Oregon, Texas
and Washington. Prior to joining MFS Communications, Mr. Callahan was Vice
President and General Manager, Southwest Division for Sprint. Mr. Callahan also
held sales positions with Data Switch and North American Telecom. Mr. Callahan
was elected to Allegiance's board of directors in March 1998.
 
     Dana A. Crowne became Allegiance's Senior Vice President and Chief Engineer
in August 1997. Prior to joining Allegiance, Mr. Crowne held various management
positions at MFS Communications from the time of its founding in 1988, where his
responsibilities included providing engineering support and overseeing budgets
for the construction of MFS Communications' networks. Mr. Crowne ultimately
became Vice President, Network Optimization for MFS Communications from January
1996 to May 1997 and managed the company's network expenses and planning and its
domestic engineering functions. Prior to joining MFS Communications, Mr. Crowne
designed and installed fiber optic transmission systems for Morrison-Knudsen and
served as a consultant on the construction of private telecommunications
networks with JW Reed and Associates.
 
     Stephen N. Holland joined Allegiance as its Senior Vice President and Chief
Information Officer in September 1997. Prior to that time, Mr. Holland held
several senior level positions involving management of or consulting on
information systems, accounting, taxation and finance. Mr. Holland's experience
includes serving as Practice Manager and Information Technology Consultant for
Oracle Corporation from June 1995 to September 1997, as Chief Financial Officer
of Petrosurance Casualty Co. from September 1992 to June 1995, as Manager of
Business Development for Electronic Data Systems, and as a partner of Price
Waterhouse. Mr. Holland's brother, Royce J. Holland, presently serves as
Allegiance's Chairman of the Board and Chief Executive Officer.
 
     Patricia E. Koide has been Allegiance's Senior Vice President of Human
Resources, Real Estate, Training Facilities and Administration since August
1997. Before then, Ms. Koide was Vice President of Corporate Services,
Facilities and Administration for WorldCom from March 1997 to August 1997. Ms.
Koide also held various management positions within MFS Communications and its
subsidiaries since 1989, including Senior Vice President of Facilities,
Administration and Purchasing for MFS Communications North America from 1996 to
1997, Senior Vice President of Human Resources, Facilities and Administration
for MFS Communications Telecom from 1994 to 1996, and Vice President of Human
Resources and Administration for MFS Communications North America from 1989 to
1993. Prior to MFS Communications, Ms. Koide was with Sprint for eight years
where she managed the company's human resources, real estate and facilities for
the Midwest.
 
     Gregg A. Long, who became Allegiance's Senior Vice President of Regulatory
and Development in September 1997, spent 11 years at Destec Energy, Inc. as
Project Development Manager -- Partnership Vice President and Director. In that
position, he was responsible for the development of gas-fired power plants from
conceptual stages through project financing. Prior to joining Destec, Mr. Long
was Manager of Project Finance at Morrison-Knudsen, where he was responsible for
analyzing and arranging finance packages for various industrial, mining and
civil projects and also served as financial consultant and analyst.
 
                                       54
<PAGE>   58
 
     Mark B. Tresnowski became Allegiance's Senior Vice President and General
Counsel in February 1999. Mr. Tresnowski has been Allegiance's Secretary since
September 1997. Mr. Tresnowski practiced law at Kirkland & Ellis for 13 years
and was a partner of that firm from October 1992 to January 1999. In private
practice, Mr. Tresnowski specialized in private and public financings, mergers
and acquisitions and securities law.
 
     Anthony J. Parella, who joined Allegiance as its Regional Vice
President -- Central Division in August 1997 and became its National Vice
President of Field Sales in August 1998, has more than 10 years of experience in
the telecommunications industry. Prior to joining Allegiance, Mr. Parella was
Vice President and General Manager for MFS Intelenet, Inc., an operating unit of
MFS Communications, from February 1994 to January 1997, where he was responsible
for the company's sales and operations in Texas. Mr. Parella also served as
Director of Commercial Sales for Sprint from 1991 to January 1994.
 
     Paul D. Carbery, who was elected to Allegiance's board of directors in
August 1997, is a general partner of Frontenac Company, a Chicago-based private
equity investing firm, where he specializes in investing in companies in the
telecommunications and technology industries. Mr. Carbery also presently serves
on the boards of directors of Whittman Hart, Inc., a publicly traded information
services company.
 
     James E. Crawford, III, who was elected to Allegiance's board of directors
in August 1997, is a general partner of Frontenac Company, a Chicago-based
private equity investing firm, where he specializes in investing in companies in
the telecommunications and technology industries. Mr. Crawford also presently
serves on the boards of directors of Focal Communications Corporation, a
privately held CLEC that will compete with Allegiance, as well as of Optika
Incorporated, a publicly held imaging software document company, and Input
Software Incorporated, a publicly held document imaging software company.
 
     John B. Ehrenkranz, who was elected to Allegiance's board of directors in
March 1998, is a Principal of Morgan Stanley & Co. Incorporated where he has
been employed since 1987. Mr. Ehrenkranz also presently serves on the board of
directors of Choice One, a privately held CLEC that may compete with Allegiance.
Mr. Ehrenkranz is also a Principal of Morgan Stanley Capital Partners III, Inc.
 
     Paul J. Finnegan, who was elected to Allegiance's board of directors in
August 1997, is a managing director of Madison Dearborn Partners, Inc., a
Chicago-based private equity investing firm, where he specializes in investing
in companies in the telecommunications industry. Mr. Finnegan also presently
serves on the boards of directors of Focal Communications Corporation, a
privately held CLEC that competes with Allegiance in certain markets, and
Omnipoint Corporation, a publicly traded PCS provider.
 
     Richard D. Frisbie, who was elected to Allegiance's board of directors in
August 1997, is a Managing Partner of Battery Partners IV, LLC which is the
general partner of Battery Venture IV, a Boston-based private equity investing
firm, where he specializes in investing in companies in the telecommunications
industry. Mr. Frisbie also presently serves on the board of directors of Focal
Communications Corporation, a privately held CLEC that competes with Allegiance
in certain markets.
 
     Alan E. Goldberg was elected to Allegiance's board of directors in March
1999. Mr. Goldberg has been Chairman, CEO and Director of Morgan Stanley Dean
Witter Capital Partners III, Inc. since February 1998. Prior to that time, he
was co-head of MSDW Capital Partners. He has been a Managing Director of Morgan
Stanley & Co. Incorporated since January 1988. Mr. Goldberg also serves as a
director of Amerin Corporation, Catalytica, Inc., Smurfit-Stone Container
Corporation, Equant, N.V., a provider of international data network services,
and several private companies.
 
     Reed E. Hundt was elected to Allegiance's board of directors in March 1998.
Mr. Hundt served as chairman of the Federal Communications Commission from 1993
to 1997. He currently serves as chairman of The Forum on Communications and
Society at The Aspen Institute, is a senior advisor on information industries to
McKinsey & Company, a worldwide management consulting firm, and a special
advisor to Madison Dearborn Partners, Inc., a Chicago-based private equity
investing firm. Mr. Hundt is a venture partner at Benchmark Capital, a venture
capital firm and a principal of Charles Ross Partners, LLC, a consulting firm.
Mr. Hundt also presently serves on the boards of directors of Ascend
                                       55
<PAGE>   59
 
Communications, Inc., a publicly traded manufacturer of wide area networking
solutions, and Novell, Inc., a publicly traded network software and Internet
solutions provider, and NorthPoint Communications Holdings, Inc., a privately
held CLEC that competes with Allegiance in certain markets. Prior to joining the
FCC, Mr. Hundt was a partner at Latham & Watkins, an international law firm.
 
     James N. Perry, Jr., who was elected to Allegiance's board of directors in
August 1997, is a managing director of Madison Dearborn Partners, Inc., a
Chicago-based private equity investing firm, where he specializes in investing
in companies in the telecommunications industry. Mr. Perry also presently serves
on the boards of directors of Focal Communications Corporation, a privately held
CLEC that competes with Allegiance in certain markets, as well as Omnipoint
Corporation, a publicly traded PCS provider, and Clearnet Communications, a
Canadian publicly traded PCS and enhanced specialized mobile radio company.
 
ELECTION OF DIRECTORS; VOTING AGREEMENT
 
     Allegiance's by-laws provide that the number of directors shall be
determined by resolution of the board of directors. The board currently consists
of 12 directors. Allegiance's by-laws provide that its directors will be elected
by plurality vote of Allegiance's stockholders, without cumulative voting. No
director may be removed from office without cause and without the vote of the
holders of a majority of the outstanding voting stock.
 
     The board of directors is divided into three classes, as nearly equal in
number as possible, with each director serving a three year term and one class
being elected at each year's annual meeting of stockholders. Messrs. Callahan,
Finnegan, Carbery and Ehrenkranz are in the class of directors whose term
expires at the 1999 annual meeting of Allegiance's stockholders. Messrs. Lord,
Yost, Crawford and Frisbie are in the class of directors whose term expires at
the 2000 annual meeting of Allegiance's stockholders. Messrs. Holland, Hundt,
Perry and Goldberg are in the class of directors whose term expires at the 2001
annual meeting of Allegiance's stockholders. At each annual meeting of
Allegiance's stockholders, successors to the class of directors whose term
expires at such meeting will be elected to serve for three-year terms and until
their successors are elected and qualified.
 
     Certain of Allegiance's stockholders have each agreed to vote all of their
shares in such a manner as to elect the following persons to serve as directors:
Madison Dearborn Capital Partners, Morgan Stanley Capital Partners, and
Frontenac Company each have the right to designate two directors; Battery
Ventures has the right to designate one director; Allegiance's Chief Executive
Officer has the right to serve as a director; our original management investors
have the right to designate three directors; and the final two directorships may
be filled by representatives designated by the fund investors and acceptable to
the management investors.
 
COMMITTEES OF THE BOARD OF DIRECTORS
 
     The board of directors currently has three committees:
 
     - an Executive Committee,
 
     - an Audit Committee, and
 
     - a Compensation Committee.
 
     The Executive Committee is currently comprised of Messrs. Holland,
Crawford, Goldberg and Perry. The Executive Committee is authorized, subject to
certain limitations, to exercise all of the powers of the board of directors
during periods between board meetings.
 
     The Audit Committee is currently comprised of Messrs. Yost, Hundt, Carbery,
Ehrenkranz and Finnegan. The Audit Committee is responsible for making
recommendations to the board of directors regarding the selection of independent
auditors, reviewing the results and scope of the audit and other
 
                                       56
<PAGE>   60
 
services provided by Allegiance's independent accountants and reviewing and
evaluating Allegiance's audit and control functions and year 2000 issues.
 
     The Compensation Committee is currently comprised of Messrs. Holland,
Frisbie, Crawford, Goldberg and Perry. The Compensation Committee is responsible
for reviewing, and as it deems appropriate, recommending to the board of
directors, policies, practices and procedures relating to the compensation of
the officers and other managerial employees of Allegiance and the establishment
and administration of employee benefit plans. The Compensation Committee
exercises all authority under any stock option or stock purchase plans of
Allegiance, unless the board appoints any other committee to exercise such
authority, and advises and consults with the officers of Allegiance as may be
requested regarding managerial personnel policies.
 
COMPENSATION OF DIRECTORS
 
     Allegiance will reimburse the members of its board of directors for their
reasonable out-of-pocket expenses incurred in connection with attending board or
committee meetings. Additionally, Allegiance is obligated to maintain its
present level of directors' and officers' insurance. Members of Allegiance's
board of directors receive no other compensation for services provided as a
director or as a member of any board committee.
 
EXECUTIVE COMPENSATION
 
     The following table sets forth compensation paid to the Chief Executive
Officer and the four other executive officers of Allegiance who, based on salary
and bonus compensation from Allegiance, were the most highly compensated
officers of Allegiance for the year ended December 31, 1998.
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                    ANNUAL COMPENSATION
                                      ------------------------------------------------
                                                                       OTHER ANNUAL         ALL OTHER
NAME AND PRINCIPAL POSITION           YEAR   SALARY($)   BONUS($)   COMPENSATION($)(A)   COMPENSATION($)
- ---------------------------           ----   ---------   --------   ------------------   ---------------
<S>                                   <C>    <C>         <C>        <C>                  <C>
Royce J. Holland....................  1998   $207,693    $150,000           $--                $--
  Chairman of the Board and           1997   $ 72,308    $     --           $--                $--
  Chief Executive Officer
C. Daniel Yost......................  1998   $165,385    $100,000           $--                $--
  President and Chief                 1997   $     --    $     --           $--                $--
  Operating Officer
Thomas M. Lord......................  1998   $181,731    $150,000           $--                $--
  Executive Vice President of         1997   $ 63,942    $     --           $--                $--
  Corporate Development and
  Chief Financial Officer
John J. Callahan....................  1998   $181,731    $ 70,000           $--                $--
  Senior Vice President of            1997   $ 10,096    $     --           $--                $--
  Sales and Marketing
Dana A. Crowne......................  1998   $152,052    $ 51,058           $--                $--
  Senior Vice President and Chief     1997   $ 45,192    $     --           $--                $--
  Engineer
</TABLE>
 
- ---------------
 
(a)  Includes perquisites and other benefits paid to the named executive officer
     in excess of 10% of the total annual salary and bonus received by the named
     executive officer during the last fiscal year.
 
     Prior to April 1998, the board did not have a Compensation Committee and
decisions concerning the compensation of executive officers and other key
employees of Allegiance were determined by Allegiance's board of directors.
 
                                       57
<PAGE>   61
 
STOCK PLANS
 
  1997 Nonqualified Stock Option Plan
 
     On November 13, 1997, Allegiance's board of directors adopted the 1997
Nonqualified Stock Option Plan, under which Allegiance may issue to its
directors, consultants, and executive and other key employees, stock options
exercisable for shares of Allegiance's common stock. Options to acquire an
aggregate of 1,037,474 shares of common stock have been granted under such
option plan and Allegiance will not grant options for any additional shares
under the option plan.
 
     The option plan is administered by the Compensation Committee and
authorizes the Compensation Committee to issue options in such forms and amounts
and on such terms as determined by the Compensation Committee. The per-share
exercise price for options is set by the Compensation Committee, but may not be
less than the fair market value of a share of Allegiance's common stock on the
date of grant, as determined in good faith by the Compensation Committee. The
terms of the options issued under the option plan to date are summarized below.
 
     Three years' amount of options will be issued on the first business day of
the quarter succeeding the date which a participant joins Allegiance. Such
options will vest over a three-year period, with 1/3 vesting on the first
anniversary of the date of grant and 1/12 vesting on each of the first eight
quarter-ends thereafter. Subject to available options under the option plan, one
year's amount of options will be issued on each anniversary of the initial
grant, and such options will vest in the third year after grant, with 1/4
vesting on each of the 27-, 30-, 33-, and 36-month anniversaries of the date of
grant. Through this mechanism, a participant will at any given time have three
years' amount of options unvested. Vesting is accelerated 100% upon an
employee's death or permanent physical disability. If there is a sale of
Allegiance and the participant is terminated or constructively terminated within
the two-year period following the sale, vesting is accelerated 100% upon such
termination.
 
     Options are nontransferable during the life of the participant and
generally expire if not exercised within six years after the date of grant.
Shares of common stock issued upon exercise of options are subject to various
restrictions on transferability, holdback periods in the event of a public
offering of Allegiance's securities and provisions requiring the holder of such
shares to approve and, if requested by Allegiance, sell its shares in any sale
of Allegiance that is approved by the board.
 
  1998 Stock Incentive Plan
 
     On June 18, 1998, the board and stockholders of Allegiance approved
Allegiance's 1998 Stock Incentive Plan. This stock incentive plan is
administered by the Compensation Committee. Certain employees, directors,
advisors and consultants of Allegiance will be eligible to participate in this
plan. The Compensation Committee is authorized to select the participants and
determine the terms and conditions of the awards under this plan. The stock
incentive plan provides for the issuance of the following types of incentive
awards: stock options, stock appreciation rights, restricted stock, performance
grants and other types of awards that the Compensation Committee deems
consistent with the purposes of the stock incentive plan.
 
     On March 2, 1999, Allegiance's board approved amending this plan to
increase the number of shares available under this plan by 2,500,000 shares. An
aggregate of 6,155,778 shares of common stock of Allegiance have been reserved
for issuance under the stock incentive plan, subject to certain adjustments
reflecting changes in Allegiance's capitalization.
 
     Options granted under the stock incentive plan may be either incentive
stock options or such other forms of non-qualified stock options as the
Compensation Committee may determine. Incentive stock
 
                                       58
<PAGE>   62
 
options are intended to qualify as "incentive stock options" within the meaning
of Section 422 of the Internal Revenue Code of 1986, as amended (the "Code").
The exercise price of
 
     - an incentive stock option granted to an individual who owns shares
       possessing more than 10% of the total combined voting power of all
       classes of stock of Allegiance will be at least 110% of the fair market
       value of a share of common stock on the date of grant, and
 
     - an incentive stock option granted to an individual other than such a 10%
       owner will be at least 100% of the fair market value of a share of common
       stock on the date of grant.
 
     Options granted under the stock incentive plan may be subject to time
vesting and certain other restrictions at the sole discretion of the
Compensation Committee.
 
     The board generally will have the power and authority to amend the stock
incentive plan at any time without approval of Allegiance's stockholders,
subject to applicable federal securities and tax laws limitations and to the
regulations of the Nasdaq National Market.
 
  Stock Purchase Plan
 
     On June 18, 1998, Allegiance's Employee Stock Discount Purchase Plan was
approved by the board and stockholders. The stock purchase plan is intended to
give employees desiring to do so a convenient means of purchasing shares of
common stock through payroll deductions. The stock purchase plan is intended to
provide an incentive to participate by permitting purchases at a discounted
price. Allegiance believes that ownership of stock by employees will foster
greater employee interest in the success, growth and development of Allegiance.
 
     Subject to certain restrictions, each employee of Allegiance who is a U.S.
resident or a U.S. citizen temporarily on location at a facility outside of the
United States will be eligible to participate in the stock purchase plan if he
or she has been employed by Allegiance for more than three continuous months.
Participation will be discretionary with each eligible employee. Allegiance has
reserved 2,305,718 shares of common stock for issuance in connection with the
stock purchase plan.
 
     Elections to participate and purchases of stock will be made on a quarterly
basis. Each participating employee contributes to the stock purchase plan by
choosing a payroll deduction in any specified amount, with a specified minimum
deduction per payroll period. A participating employee may increase or decrease
the amount of such employee's payroll deduction, including a change to a zero
deduction as of the beginning of any calendar quarter. Elected contributions
will be credited to participants' accounts at the end of each calendar quarter.
 
     Each participating employee's contributions will be used to purchase shares
for the employee's share account as promptly as practicable after each calendar
quarter. The cost per share will be 85% of the lower of the closing price of
Allegiance's common stock on the Nasdaq National Market on the first or the last
day of the calendar quarter. The number of shares purchased on each employee's
behalf and deposited in his/her share account will be based on the amount
accumulated in such participant's cash account and the purchase price for shares
with respect to any calendar quarter. Shares purchased under the stock purchase
plan carry full rights to receive dividends declared from time to time. A
participating employee will have full ownership of all shares in such employee's
share account and may withdraw them for sale or otherwise by written request to
the Compensation Committee following the close of each calendar quarter.
 
     Subject to applicable federal securities and tax laws, the board will have
the right to amend or to terminate the stock purchase plan. Amendments to the
stock purchase plan will not affect a participating employee's right to the
benefit of the contributions made by such employee prior to the date of any such
amendment. In the event the stock purchase plan is terminated, the Compensation
Committee will be required to distribute all shares held in each participating
employee's share account plus an amount of cash equal to the balance in each
participating employee's cash account.
 
                                       59
<PAGE>   63
 
  401(k) Plan
 
     Allegiance has adopted a tax-qualified employee savings and retirement plan
covering all of Allegiance's full-time employees. Under the 401(k) plan,
employees may elect to reduce their current compensation up to the statutorily
prescribed annual limit and have the amount of such reduction contributed to the
401(k) plan. The 401(k) plan is intended to qualify under Section 401 of the
Code so that contributions by employees to the 401(k) plan, and income earned on
plan contributions, are not taxable to employees until withdrawn from the 401(k)
plan. The trustees under the 401(k) plan, at the direction of each participant,
invest such participant's assets in the 401(k) plan in selected investment
options.
 
EXECUTIVE AGREEMENTS
 
  Royce J. Holland Executive Agreement
 
     In August 1997, Allegiance, Allegiance Telecom, LLC, and Mr. Holland
entered into an Executive Purchase Agreement and other agreements that include,
among others, the following terms:
 
          Vesting. The Allegiance Telecom, LLC securities purchased by Mr.
     Holland, as well as any Allegiance securities distributed with respect to
     such Allegiance Telecom, LLC securities are subject to vesting over a
     four-year period, with 20% vesting on the date of grant and 20% vesting on
     each of the first four anniversaries of the grant date. Vesting was
     accelerated by one year upon the consummation of the initial public
     offering of common stock, and will be accelerated 100% in the event of Mr.
     Holland's death or disability, and 100% upon a sale of Allegiance where at
     least 50% of the consideration for such sale is cash or marketable
     securities.
 
          Repurchase of Securities. If Mr. Holland's employment is terminated
     for any reason other than a termination by Allegiance without cause,
     Allegiance will have the right to repurchase all unvested Holland executive
     securities at the lesser of fair market value and original cost.
 
          Restrictions on Transfer; Holdback and "Drag Along" Agreements. The
     Holland executive securities are subject to various restrictions on
     transferability, holdback periods in the event of a public offering of
     Allegiance's securities and provisions requiring the holder of such shares
     to approve and, if requested by Allegiance, sell its shares in any sale of
     Allegiance that is approved by the board.
 
          Terms of Employment. Mr. Holland is an "at will" employee of
     Allegiance and, thus, may be terminated by Allegiance at any time and for
     any reason. Mr. Holland is not entitled to receive any severance payments
     upon any such termination, other than payments in consideration of the
     noncompetition and nonsolicitation agreements discussed below.
 
          Noncompetition and Nonsolicitation Agreements. During the noncompete
     period defined below, Mr. Holland may not hire or attempt to induce any
     employee of Allegiance to leave Allegiance's employ, nor attempt to induce
     any customer or other business relation of Allegiance to cease doing
     business with Allegiance, nor in any other way interfere with Allegiance's
     relationships with its employees, customers, and other business relations.
     Also, during this noncompete period, Mr. Holland may not participate in any
     business engaged in the provision of telecommunications services in the
     markets specified below.
 
          The noncompete period in this agreement is the period of employment
     and the following additional period: (a) if Mr. Holland is terminated prior
     to August 13, 2000, the period ending on the later of August 13, 2001 and
     the second anniversary of termination; (b) if Mr. Holland is terminated at
     any time on or after August 13, 2000 but prior to August 13, 2001, the
     period ending on August 13, 2002; and (c) if Mr. Holland is terminated at
     any time on or after August 13, 2001, the one-year period following
     termination. Mr. Holland will receive, as consideration for his noncompete,
     100% of his base salary that he received, as compensation from Allegiance
     immediately prior to his termination, as well as a continuation of his
     medical benefits. However, this period ends if at any time
 
                                       60
<PAGE>   64
 
     Allegiance ceases to pay Mr. Holland the base salary and benefits. The
     markets covered by this noncompete provision are:
 
        - any market in which Allegiance is conducting business or preparing
          under a business plan approved by the board of directors to conduct
          business;
 
        - Dallas, New York City, Atlanta, Chicago, Los Angeles and 15 additional
          markets; and
 
        - any market for which Allegiance has prepared a business plan unless
          such business plan has been rejected by the board of directors.
 
  C. Daniel Yost Executive Agreement
 
     In February 1998, Allegiance Telecom, Allegiance Telecom, LLC, and Mr. Yost
entered into an Executive Purchase Agreement, containing the same terms as those
in Mr. Holland's executive agreement.
 
  Thomas M. Lord Executive Agreement
 
     In August 1997, Allegiance, Allegiance Telecom, LLC, and Mr. Lord entered
into an Executive Purchase Agreement, containing the same terms as those in Mr.
Holland's executive agreement.
 
EXECUTIVE AGREEMENTS ENTERED INTO BY OTHER MANAGEMENT INVESTORS
 
     Each of the original management investors has entered into an Executive
Purchase Agreement and other agreements which include the following terms:
 
          Vesting. The Allegiance Telecom, LLC securities purchased by a
     management investor, as well as any securities distributed with respect to
     such Allegiance Telecom, LLC securities are subject to vesting over a
     four-year period, with 25% vesting on each of the first four anniversaries
     of the grant date. Vesting was accelerated by one year upon the
     consummation of the initial public offering of common stock, and will be
     accelerated 100% in the event of such management investor's death or
     disability, and 100% upon a sale of Allegiance where at least 50% of the
     consideration for such sale is cash or marketable securities.
 
          Repurchase of Securities. If a management investor's employment is
     terminated for any reason, Allegiance will have the right to repurchase all
     such management investor's unvested executive securities at the lesser of
     fair market value and original cost.
 
          Restrictions on Transfer; Holdback and "Drag Along" Agreements. The
     executive securities are subject to various restrictions on
     transferability, holdback periods in the event of a public offering of
     Allegiance's securities and provisions requiring the holder of such shares
     to approve and, if requested by Allegiance, sell its shares in any sale of
     Allegiance that is approved by the board.
 
          Terms of Employment. Each management investor is an "at will" employee
     of Allegiance and, thus, may be terminated by Allegiance at any time and
     for any reason. No management investor is entitled to receive any severance
     payments upon any such termination.
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
     Prior to April 1998, Allegiance did not have a Compensation Committee and
the compensation of executive officers and other key employees of Allegiance was
determined by its board of directors. Royce J. Holland, Allegiance's Chairman
and Chief Executive Officer, Thomas M. Lord, Allegiance's Executive Vice
President of Corporate Development and Chief Financial Officer, C. Daniel Yost,
Allegiance's President and Chief Operating Officer, and John J. Callahan,
Allegiance's Senior Vice President of Sales and Marketing, are all currently
members of Allegiance's board of directors. The board of directors has
established a Compensation Committee, which is responsible for decisions
regarding salaries, incentive compensation, stock option grants and other
matters regarding executive officers and key employees of Allegiance. See
"-- Committees of the Board of Directors."
 
                                       61
<PAGE>   65
 
                 CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS
 
LIMITED LIABILITY COMPANY AGREEMENT
 
     On August 13, 1997, Allegiance's original fund investors and management
investors entered into a limited liability company agreement to govern the
affairs of Allegiance Telecom, LLC, which immediately prior to the initial
public offering, held the one outstanding share of Allegiance's common stock and
substantially all of the outstanding shares of Allegiance's preferred stock.
 
     Upon consummation of Allegiance's initial public offering of common stock,
Allegiance Telecom, LLC dissolved and its assets, which consisted almost
entirely of Allegiance stock, were distributed to the fund investors and the
management investors in accordance with its limited liability company agreement.
Under the terms of this agreement, the equity allocation between the fund
investors and the management investors could range between 95.0%/5.0% and
66.7%/33.3% based upon the valuation of Allegiance's common stock implied by the
initial public offering of common stock. Based upon the valuation of
Allegiance's common stock implied by the initial public offering of common
stock, the equity allocation was 66.7% to the fund investors and 33.3% to the
management investors. See "Management's Discussion and Analysis of Financial
Condition and Results of Operations -- Results of Operations."
 
SECURITYHOLDERS AGREEMENT
 
     The fund investors, the management investors, and Allegiance, are parties
to a Securityholders Agreement dated as of August 13, 1997. Under the terms of
this agreement, in the event of an approved sale of Allegiance, each of the fund
investors, management investors and their transferees agrees to approve and, if
requested, to sell its shares in such sale of Allegiance. Most of the other
provisions of this agreement terminated upon the consummation of the initial
public offering of common stock.
 
REGISTRATION AGREEMENT
 
     The fund investors, the management investors, and Allegiance are parties to
a Registration Agreement dated as of August 13, 1997. See "Description of
Capital Stock -- Registration Rights."
 
VOTING AGREEMENT
 
     Certain of Allegiance's stockholders have each agreed to vote all of their
shares in such a manner as to elect the following persons to serve as directors:
Madison Dearborn Capital Partners, Morgan Stanley Capital Partners, and
Frontenac Company each have the right to designate two directors; Battery
Ventures has the right to designate one director; Allegiance's Chief Executive
Officer has the right to serve as a director; the management investors have the
right to designate three directors; and the final two directorships may be
filled by representatives designated by the fund investors and acceptable to the
management investors.
 
GRANT OF OPTIONS
 
     In March 1998, prior to Reed E. Hundt joining the board of directors,
Allegiance issued:
 
     - options to purchase 50,623 shares of common stock to Reed E. Hundt, and
 
     - 50,623 shares of common stock to Charles Ross Partners, LLC, of which Mr.
       Hundt is a member.
 
     The options were issued with an exercise price of $2.47 per share. 33.33%
of such options vested on March 13, 1999, and an additional 8.34% of such
options will vest every three months after this date, until March 13, 2001, when
all such options become exercisable. These numbers take into account
Allegiance's initial public offering of common stock and related
426.2953905-for-one stock split.
 
                                       62
<PAGE>   66
 
OTHER
 
     Morgan Stanley & Co. Incorporated, an affiliate of Morgan Stanley Capital
Partners, one of the fund investors, acted as a placement agent in connection
with Allegiance's offering of the 11 3/4% notes and redeemable warrants and
received fees of approximately $4.4 million. In addition, Morgan Stanley & Co.
Incorporated was one of the underwriters in Allegiance's initial public offering
of common stock and 12 7/8% notes offering and received fees of approximately
$6.9 million in connection with such offerings.
 
                                       63
<PAGE>   67
 
                       PRINCIPAL AND SELLING STOCKHOLDERS
 
     The following table sets forth certain information regarding the beneficial
ownership of the outstanding common stock of Allegiance as of April 8, 1999 by:
 
     - each of the directors and the executive officers of Allegiance,
 
     - all directors and executive officers as a group,
 
     - each selling stockholder, and
 
     - each owner of more than 5% of the equity securities of Allegiance.
 
     The percentages specified below are based on 50,389,115 shares of common
stock outstanding as of April 8, 1999 and on 62,215,115 shares of common stock
outstanding after the offering. Unless otherwise noted, the address for each
director and executive officer of Allegiance is c/o Allegiance Telecom, Inc.,
1950 Stemmons Freeway, Suite 3026, Dallas, Texas 75207.
 
<TABLE>
<CAPTION>
                                             SHARES BENEFICIALLY                     SHARES BENEFICIALLY
                                           OWNED PRIOR TO OFFERING                   OWNED AFTER OFFERING
                                           ------------------------                  --------------------
                                                           PERCENT    SHARES TO BE                PERCENT
                                                             OF         SOLD IN                     OF
NAME AND ADDRESS OF BENEFICIAL OWNER          NUMBER        CLASS       OFFERING       NUMBER      CLASS
- ------------------------------------       ------------   ---------   ------------   ----------   -------
<S>                                        <C>            <C>         <C>            <C>          <C>
DIRECTORS AND EXECUTIVE OFFICERS:
Royce J. Holland(1)......................    3,908,223       7.8%             --      3,908,223     6.3%
C. Daniel Yost...........................    1,619,940       3.2              --      1,619,940     2.6
Thomas M. Lord(2)........................    1,822,432       3.6              --      1,822,432     2.9
John J. Callahan.........................      608,477       1.2              --        608,477     1.0
Dana A. Crowne...........................      404,985         *              --        404,985       *
Paul D. Carbery(3).......................    4,262,999       8.5         850,000(5)   3,412,999     5.5
James E. Crawford, III(3)(4).............    4,274,499       8.5         850,000(5)   3,424,499     5.5
John B. Ehrenkranz.......................           --        --              --             --      --
Paul J. Finnegan(6)......................           --        --              --             --      --
Richard D. Frisbie(7)....................    2,131,499       4.2              --      2,131,499     3.4
Alan E. Goldberg(8)......................           --        --              --             --      --
Reed E. Hundt(9).........................      101,246         *              --        101,246       *
James N. Perry, Jr.(6)...................           --        --              --             --      --
All directors and executive officers as a
  group (13 persons).....................   14,871,281      29.6         850,000(5)  14,021,281    22.5
5% OWNERS:
Madison Dearborn Capital Partners(10)....   10,302,247      20.4       2,000,000      8,302,247    13.3
Morgan Stanley Capital Partners(11)......   10,302,247      20.4              --     10,302,247    16.6
Frontenac Company(12)....................    4,262,999       8.5         850,000      3,412,999     5.5
</TABLE>
 
- ---------------
 
  *  Denotes less than one percent.
 
 (1) Includes 1,940,552 shares of common stock owned by the Royce J. Holland
     Family Limited Partnership, of which Royce J. Holland is the sole general
     partner, 1,000 shares of common stock owned by Mr. Holland's wife, 2,600
     shares of common stock held by Mr. Holland as custodian for his children,
     as to which 2,600 shares Mr. Holland disclaims beneficial ownership.
     3,881,105 of the shares of common stock owned by Mr. Holland and the Royce
     J. Holland Family Limited Partnership are subject to vesting, with 60% of
     such shares of common stock having vested and an additional 20% vesting on
     each of August 13, 1999 and 2000. See "Management -- Executive Agreements."
 
 (2) Includes 911,216 shares of common stock owned by Mr. Lord's wife and
     children, as to which Mr. Lord disclaims beneficial ownership. All of the
     shares of common stock owned by Mr. Lord and his family are subject to
     vesting with 60% of such shares of common stock having vested and an
 
                                       64
<PAGE>   68
 
     additional 20% vesting on each of August 13, 1999 and 2000. See
     "Management -- Executive Agreements."
 
 (3) 4,262,999 shares of common stock shown are owned by Frontenac VII Limited
     Partnership and Frontenac Masters VII Limited Partnership. Messrs. Carbery
     and Crawford are members of Frontenac Company, VII, L.L.C., the general
     partner of Frontenac VII Limited Partnership and Frontenac Masters VII
     Limited Partnership and their address is c/o Frontenac Company, 135 S.
     LaSalle Street, Suite 3800, Chicago, IL 60603. They disclaim beneficial
     ownership of these shares of common stock.
 
 (4) Includes 500 shares of common stock owned by Mr. Crawford's spouse, 100
     shares of common stock owned by Mr. Crawford's son, and 600 shares held by
     Mr. Crawford as custodian for his son, as to which 600 shares Mr. Crawford
     disclaims beneficial ownership.
 
 (5) Represents shares being sold by the Frontenac funds. Neither Mr. Carbery
     nor Mr. Crawford are selling any shares in their individual capacity.
 
 (6) Messrs. Finnegan and Perry are managing directors of Madison Dearborn
     Partners, Inc., the general partner of the general partner of Madison
     Dearborn Capital Partners II, L.P. and their address is c/o Madison
     Dearborn Partners, Inc., Three First National Plaza, Suite 3800, Chicago,
     IL 60602.
 
 (7) All shares of common stock shown are owned by Battery Ventures IV, L.P. and
     Battery Investment Partners IV, LLC. Mr. Frisbie is a member manager of
     Battery Partners IV, LLC, the general partner of Battery Ventures IV, L.P.
     and a member manager of Battery Investment Partners IV, LLC and his address
     is c/o Battery Ventures, 20 William Street, Wellesley, MA 02181. He
     disclaims beneficial ownership of these shares of common stock.
 
 (8) Mr. Goldberg is Chairman, CEO and Director of Morgan Stanley Capital
     Partners III, Inc., the general partner of the general partner of the funds
     described in footnote (10) below and their address is c/o Morgan Stanley
     Capital Partners, 1221 Avenue of the Americas, New York, NY 10020.
 
 (9) Mr. Hundt owns options to acquire 50,623 shares of common stock and Charles
     Ross Partners, LLC, a Delaware limited liability company, of which Mr.
     Hundt is a member, owns 50,623 shares of common stock.
 
(10) These shares of common stock are owned by Madison Dearborn Capital Partners
     II, L.P.
 
(11) These shares of common stock are owned by Morgan Stanley Capital Partners
     III, L.P., MSCP III 892 Investors, L.P. and Morgan Stanley Capital
     Investors, L.P.
 
(12) These shares of common stock are owned by Frontenac VII Limited Partnership
     and Frontenac Masters VII Limited Partnership.
 
                                       65
<PAGE>   69
 
                      DESCRIPTION OF CERTAIN INDEBTEDNESS
 
11 3/4% NOTES
 
     On February 3, 1998, we issued $445.0 million aggregate principal amount at
maturity of 11 3/4% Senior Discount Notes. They will mature on February 15,
2008. The 11 3/4% notes were issued in units, with each unit consisting of one
11 3/4% note and one redeemable warrant.
 
     No cash interest is payable on the 11 3/4% notes prior to August 15, 2003.
From and after February 15, 2003, interest on the 11 3/4% notes will accrue at
the rate of 11 3/4% per annum. Interest on the 11 3/4% notes is payable
semiannually on February 15 and August 15 of each year, commencing August 15,
2003. Payment of interest will be made to holders of record at the close of
business on the February 1 or August 1 immediately preceding the interest
payment date.
 
     The 11 3/4% notes are not secured by any of our assets and rank equally in
right of payment with all of our unsubordinated and unsecured indebtedness,
including the 12 7/8% notes described below. The 11 3/4% notes are senior in
right of payment to all of our future subordinated indebtedness.
 
     We may redeem the 11 3/4% notes at our option, in whole or in part, at any
time on or after February 15, 2003. The initial redemption price is 105.8750% of
their principal amount at maturity, plus accrued interest. The redemption price
will decline each year and will be 100% of their principal amount at maturity,
plus accrued interest, beginning on February 15, 2006. In addition, at any time
on or before February 15, 2001, we may redeem up to 35% of the aggregate
principal amount at maturity of the 11 3/4% notes with the proceeds of certain
public equity offerings at a redemption price equal to 111.75% of their accreted
value on the redemption date. We may make this redemption only so long as at
least $289.3 million aggregate principal amount at maturity of the 11 3/4% notes
remains outstanding immediately after such redemption.
 
     The 11 3/4% notes indenture contains certain restrictive covenants,
including among others limitations on the ability of Allegiance and its
restricted subsidiaries to:
 
     - incur indebtedness,
 
     - pay dividends,
 
     - prepay subordinated indebtedness,
 
     - repurchase capital stock,
 
     - make investments,
 
     - engage in transactions with affiliates,
 
     - create liens,
 
     - sell assets, and
 
     - engage in mergers and consolidations and certain other events which could
       cause an event of default.
 
     Events of default under the 11 3/4% notes indenture include, among other
things:
 
     - payment defaults,
 
     - covenant defaults,
 
     - cross-defaults to certain other indebtedness,
 
     - judgment defaults, and
 
     - certain events of bankruptcy and insolvency.
 
                                       66
<PAGE>   70
 
12 7/8% NOTES
 
     On July 7, 1998, we issued $205.0 million aggregate principal amount at
maturity of 12 7/8% Senior Notes. They will mature on May 15, 2008.
 
     Interest on the 12 7/8% notes accrues at the rate of 12 7/8% per annum,
payable semiannually on May 15 and November 15 of each year. Payment of interest
will be made to holders of record at the close of business on the May 1 or
November 1 immediately preceding the interest payment date.
 
     In connection with the sale of the 12 7/8% notes, we purchased
approximately $69.0 million of U.S. Government securities and placed such
securities in a pledge account to be used for payment in full of the first six
scheduled interest payments due on the 12 7/8% notes.
 
     The 12 7/8% notes are not secured by any of our assets other than the
pledge of the U.S. Government securities described above, and rank equally in
right of payment with all of our unsubordinated and unsecured indebtedness,
including the 11 3/4% notes described above. The 12 7/8% notes are senior in
right of payment to all of our future subordinated indebtedness.
 
     We may redeem the 12 7/8% notes at our option, in whole or in part, at any
time on or after May 15, 2003. The initial redemption price is 106.438% of their
principal amount at maturity, plus accrued interest. The redemption price will
decline each year and will be 100% of their principal amount at maturity, plus
accrued interest, beginning on May 15, 2006. In addition, at any time on or
before May 15, 2001, we may redeem up to 35% of the aggregate principal amount
at maturity of the 12 7/8% notes with the proceeds of certain public equity
offerings at a redemption price equal to 112.875% of the principal amount plus
accrued interest. We may make this redemption only so long as at least $133.25
million aggregate principal amount at maturity of the 12 7/8% notes remains
outstanding immediately after such redemption.
 
     The 12 7/8% notes indenture contains certain restrictive covenants and
events of default that are substantially similar to those contained in the
11 3/4% indenture.
 
REVOLVING CREDIT FACILITY
 
     On April 1, 1999, we entered into a credit agreement and related guaranty
agreement with Goldman Sachs Credit Partners L.P., TD Securities (USA) Inc.,
Morgan Stanley Senior Funding, Inc. and various other lenders that provides for
a $225 million senior secured revolving credit facility maturing December 31,
2005 for a subsidiary of Allegiance Telecom, Inc. This revolving facility is
available, subject to satisfaction of certain terms and conditions, to provide
purchase money financing for the acquisition, construction and improvement of
telecommunications assets by Allegiance's operating subsidiaries. The following
is a summary of material terms of the revolving credit facility.
 
     The borrower under the facility is Allegiance Finance Company, Inc., a
wholly owned subsidiary of Allegiance Telecom, Inc. that will own Allegiance's
operating subsidiaries. The facility is structurally senior to all of
Allegiance's 12 7/8% notes and 11 3/4% notes issued in 1998. The facility is
secured by all of Allegiance's subsidiaries' assets and a pledge of the stock of
Allegiance Finance Company. The facility is guaranteed by Allegiance Telecom,
Inc. Based on Allegiance's current business plan, the facility is expected to be
undrawn until 2000. Interest rates under the facility are tied to the level of
debt compared to consolidated EBITDA and are initially expected to be the London
Interbank Offering Rate + 3.75%. The commitment fee on the undrawn portion of
the facility is 1.50% of the total amount of the facility, with step-downs based
on utilization.
 
     Allegiance's ability to borrow under the facility fluctuates according to
Allegiance's ability to meet the financial covenants and the ability of
Allegiance's geographic markets to generate cash. Allegiance may borrow under
the facility at such time as Allegiance Telecom, Inc. has invested a minimum of
$250 million in the operations of the borrower and/or its subsidiaries, and
certifies that, in at least one market which operates as an independent business
unit, Allegiance has achieved positive earnings before deducting interest,
taxes, depreciation and amortization and before deducting overhead charges. The
facility refers to this measurement as "pre-overhead EBITDA." Allegiance must
also certify that it
 
                                       67
<PAGE>   71
 
projects such market to remain pre-overhead EBITDA positive through the maturity
of the facility. The actual amount available under the initial availability test
is equal to one-third of the total amount of the facility, plus three times the
annualized pre-overhead EBITDA for such market. Thus, for example, if the
Allegiance Dallas market operations turn pre-overhead EBITDA positive for one
month and Allegiance projects that this market will remain positive through the
maturity of the facility on December 31, 2005, the initial availability under
the facility will be equal to one third of the total amount of the facility plus
three times the annualized pre-overhead EBITDA for the Dallas market. The
one-month results are annualized by multiplying these results by twelve.
Allegiance would not be able to borrow if the market fails to remain
pre-overhead EBITDA positive and is required to repay loans at such time in an
amount equal to the availability created by such market.
 
     The availability derived from any single pre-overhead EBITDA positive
market, however, will not exceed $100 million. At present, it is anticipated
that Dallas will be the first market to turn positive on a pre-overhead EBITDA
basis. Management expects this to occur in April 1999, however, there can be no
assurance that this will be the case.
 
     The amount available will increase when two or more markets generate
positive pre-overhead EBITDA for a given month. This incremental availability
will equal three times the annualized pre-overhead EBITDA generated by each
market other than the first market.
 
     The availability test also serves as a financial covenant, and Allegiance
is required to maintain levels of pre-overhead EBITDA from individual markets
that would support amounts outstanding under the facility. The commitments of
the lenders under the facility will reduce in twelve consecutive quarterly
installments, beginning on March 31, 2003, in annual amounts equal to the
following respective percentages of the initial amount of the facility:
 
<TABLE>
<CAPTION>
                                                     FACILITY
YEAR                                                 REDUCTION
- ----                                                 ---------
<S>                                                  <C>
2003..............................................      20%
2004..............................................      30%
2005..............................................      50%
</TABLE>
 
     A comprehensive covenant package as well as the availability tests
described above governs the facility. From April 1, 1999 through June 30, 2001,
Allegiance's performance will be tested by one set of covenants. Another set of
covenants will take effect July 1, 2001. Allegiance must be in compliance with
each covenant in order to borrow under the facility and a failure to satisfy any
of the covenants would enable the lender to declare outstanding amounts to be
due and payable. The covenants for these periods include:
 
<TABLE>
<CAPTION>
    COVENANTS THROUGH JUNE 30, 2001         COVENANTS FROM JULY 1, 2001 TO DECEMBER 31, 2005
    -------------------------------         ------------------------------------------------
<S>                                         <C>
- - Minimum Revenues                          - Senior Secured Debt to Annualized Consolidated
                                              EBITDA
- - Maximum Consolidated EBITDA Loss/
  Minimum Consolidated EBITDA               - Total Debt to Annualized Consolidated EBITDA
- - Senior Secured Debt to Total              - Annualized Consolidated EBITDA/Interest
Capitalization                              Expense
- - Maximum Capital Expenditures              - Annualized Pro Forma Consolidated EBITDA/Pro
                                              Forma Debt Service
- - Maximum Unsecured Subordinated Debt
                                            - Maximum Capital Expenditures
</TABLE>
 
     Allegiance has flexibility under the facility to make unlimited
acquisitions using equity consideration, or if financed with indebtedness,
acquisitions totaling up to $75 million. There is an additional $25 million
sub-limit with respect to acquisitions of entities generating negative free cash
flow for the trailing twelve-
 
                                       68
<PAGE>   72
 
month period, stepping up to $45 million at such time as the borrower generates
positive pre-overhead EBITDA in two or more markets, all of which limits are
subject to increase as additional equity is raised and contributed as common
equity to the borrower and its subsidiaries.
 
     In addition, the borrower is subject to limitations, to be determined, with
respect to investments in more than 24 initial markets. The borrower is
permitted to make distributions to Allegiance Telecom, Inc. to enable the
payment of interest and principal on the existing indebtedness of Allegiance
Telecom, Inc.
 
     The facility is also subject to certain representations, warranties,
covenants and events of default customary for credits of this nature and
otherwise agreed upon by the parties.
 
                          DESCRIPTION OF CAPITAL STOCK
 
GENERAL MATTERS
 
     The total amount of authorized capital stock of Allegiance consists of
150,000,000 shares of common stock, par value $.01 per share, and 1,000,000
shares of preferred stock, par value $.01 per share. As of April 8, 1999,
50,389,115 shares of common stock were issued and outstanding and no shares of
preferred stock were issued and outstanding. The following discussion describes
Allegiance's capital stock, its charter and by-laws. This summary describes all
material provisions of Allegiance's charter and by-laws. If you would like to
read copies of these documents, we have filed copies with the SEC.
 
     Allegiance's charter and by-laws contain certain provisions that are
intended to enhance the likelihood of continuity and stability in the
composition of the board of directors. These provisions may have the effect of
delaying, deferring or preventing a future takeover or change in control of
Allegiance unless the takeover or change in control is approved by the board of
directors.
 
COMMON STOCK
 
     Subject to the prior rights of the holders of any preferred stock, the
holders of outstanding shares of common stock are entitled to receive dividends
out of assets legally available at such time and in such amounts as the board of
directors may from time to time determine. The shares of common stock are not
convertible and the holders have no preemptive or subscription rights to
purchase any securities of Allegiance. Upon liquidation, dissolution or winding
up of Allegiance, the holders of common stock are entitled to receive pro rata,
the assets of Allegiance which are legally available for distribution, after
payment of all debts and other liabilities and subject to the prior rights of
any holders of preferred stock then outstanding. Each outstanding share of
common stock is entitled to one vote on all matters submitted to a vote of
stockholders. There is no cumulative voting.
 
PREFERRED STOCK
 
     Allegiance's board of directors may, without further action by Allegiance's
stockholders, from time to time, direct the issuance of shares of preferred
stock in series and may, at the time of issuance, determine the rights,
preferences and limitations of each series. Satisfaction of any dividend
preferences of outstanding shares of preferred stock would reduce the amount of
funds available for the payment of dividends on shares of common stock. Holders
of shares of preferred stock may be entitled to receive a preference payment in
the event of any liquidation, dissolution or winding-up of Allegiance before any
payment is made to the holders of shares of common stock. Under certain
circumstances, the issuance of shares of preferred stock may render more
difficult or tend to discourage a merger, tender offer or proxy contest, the
assumption of control by a holder of a large block of Allegiance's securities or
the removal of incumbent management. Upon the affirmative vote of a majority of
the total number of directors then in office, the board of directors of
Allegiance, without stockholder approval, may issue shares of preferred stock
with voting and conversion rights which could adversely affect the holders of
shares of common stock. There are no shares of preferred stock currently
outstanding, and Allegiance has no present intention to issue any shares of
preferred stock.
 
                                       69
<PAGE>   73
 
CERTAIN PROVISIONS OF ALLEGIANCE'S CHARTER AND BY-LAWS
 
     Allegiance's charter provides for the board of directors to be divided into
three classes, as nearly equal in number as possible, serving staggered terms.
Approximately one-third of the board of directors will be elected each year. See
"Management." Under the Delaware General Corporation Law, directors serving on a
classified board can only be removed for cause. The provision for a classified
board could prevent a party who acquires control of a majority of the
outstanding voting stock from obtaining control of the board of directors until
the second annual stockholders meeting following the date the acquiror obtains
the controlling stock interest. The classified board provision could have the
effect of discouraging a potential acquiror from making a tender offer or
otherwise attempting to obtain control of Allegiance and could increase the
likelihood that incumbent directors will retain their positions.
 
     Allegiance's charter provides that stockholder action can be taken only at
an annual or special meeting of stockholders and cannot be taken by written
consent in lieu of a meeting. Allegiance's charter and the by-laws provides
that, except as otherwise required by law, special meetings of the stockholders
can only be called under a resolution adopted by a majority of the board of
directors or by the Chief Executive Officer of Allegiance. Stockholders will not
be permitted to call a special meeting or to require the board of directors to
call a special meeting.
 
     Allegiance's by-laws establish an advance notice procedure for stockholder
proposals to be brought before an annual meeting of stockholders of Allegiance,
including proposed nominations of persons for election to the board of
directors.
 
     Stockholders at an annual meeting may only consider proposals or
nominations specified in the notice of meeting or brought before the meeting by
or at the direction of the board of directors or by a stockholder who was a
stockholder of record on the record date for the meeting, who is entitled to
vote at the meeting and who has given to Allegiance's Secretary timely written
notice, in proper form, of the stockholder's intention to bring that business
before the meeting. Although the by-laws do not give the board of directors the
power to approve or disapprove stockholder nominations of candidates or
proposals regarding other business to be conducted at a special or annual
meeting, the by-laws may have the effect of precluding the conduct of certain
business at a meeting if the proper procedures are not followed or may
discourage or defer a potential acquiror from conducting a solicitation of
proxies to elect its own slate of directors or otherwise attempting to obtain
control of Allegiance.
 
     Allegiance's charter and by-laws provide that the affirmative vote of
holders of at least 66 2/3% of the total votes eligible to be cast in the
election of directors is required to amend, alter, change or repeal certain of
their provisions. This requirement of a super-majority vote to approve
amendments to its charter and by-laws could enable a minority of Allegiance's
stockholders to exercise veto power over any such amendments.
 
CERTAIN PROVISIONS OF DELAWARE LAW
 
     Allegiance is subject to the "Business Combination" provisions of the
Delaware General Corporation Law. In general, such provisions prohibit a
publicly held Delaware corporation from engaging in various "business
combination" transactions with any "interested stockholder" for a period of
three years after the date of the transaction which the person became an
"interested stockholder," unless:
 
     - the transaction is approved by the board of directors prior to the date
       the "interested stockholder" obtained such status;
 
     - upon consummation of the transaction which resulted in the stockholder
       becoming an "interested stockholder," the "interested stockholder," owned
       at least 85% of the voting stock of the corporation outstanding at the
       time the transaction commenced, excluding for purposes of determining the
       number of shares outstanding those shares owned by:
 
      (a) persons who are directors and also officers, and
 
                                       70
<PAGE>   74
 
      (b) employee stock plans in which employee participants do not have the
          right to determine confidentially whether shares held subject to the
          plan will be tendered in a tender or exchange offer; or
 
     - on or subsequent to such date the "business combination" is approved by
       the board of directors and authorized at an annual or special meeting of
       stockholders by the affirmative vote of at least 66 2/3% of the
       outstanding voting stock which is not owned by the "interested
       stockholder."
 
     A "business combination" is defined to include mergers, asset sales and
other transactions resulting in financial benefit to a stockholder. In general,
an "interested stockholder" is a person who, together with affiliates and
associates, owns or within three years did own, 15% or more of a corporation's
voting stock. The statute could prohibit or delay mergers or other takeover or
change in control attempts with respect to Allegiance and, accordingly, may
discourage attempts to acquire Allegiance.
 
LIMITATIONS ON LIABILITY AND INDEMNIFICATION OF OFFICERS AND DIRECTORS
 
     Allegiance's charter limits the liability of directors to the fullest
extent permitted by the Delaware General Corporation Law. In addition, the
charter provides that Allegiance will indemnify directors and officers of
Allegiance to the fullest extent permitted by such law. Allegiance has entered
into indemnification agreements with its current directors and anticipates
entering into such agreements with its executive officers and any new directors
or executive officers.
 
WARRANTS
 
     In connection with the offering of our 11 3/4% notes, Allegiance issued
445,000 redeemable warrants under the Warrant Agreement between Allegiance and
The Bank of New York.
 
     Each redeemable warrant is exercisable to purchase 1.45898399509 shares of
common stock at an exercise price of $.01 per share, subject to adjustment. The
redeemable warrants may be exercised at any time on or after February 3, 1999
and prior to February 3, 2008. Upon the occurrence of a merger with a person
that does not have a class of equity securities registered under the Securities
Exchange Act of 1934, as amended in connection with which the consideration to
stockholders of Allegiance is not all cash, Allegiance or its successor by
merger or consolidation will be required to offer to repurchase the redeemable
warrants. All such repurchases will be at the market price of the common stock
or other securities issuable upon exercise of the redeemable warrants or, if the
common stock or such other securities are not registered under the Exchange Act,
the value of the common stock or other securities as determined by an
independent financial expert, less the exercise price.
 
REGISTRATION RIGHTS
 
     The fund investors, the management investors, and Allegiance are parties to
a Registration Agreement dated as of August 13, 1997. Each of Morgan Stanley
Capital Partners, Madison Dearborn Capital Partners, and Frontenac Company is
entitled to demand two long-form registrations and unlimited short-form
registrations, and Battery Ventures is entitled to demand one long-form
registration, such as registration on Form S-1, and unlimited short-form
registrations, such as registration on Form S-3. In addition, the fund investors
and the management investors may "piggyback" on primary or secondary registered
public offerings of Allegiance's securities. Allegiance has agreed to pay the
registration expenses in connection with these demand and "piggyback"
registrations. Each fund investor and management investor is subject to holdback
restrictions in the event of a public offering of Allegiance securities. The
parties to the Registration Agreement have agreed to permit the holders of
redeemable warrants to "piggyback" on any registrations under the Registration
Agreement. Allegiance has obtained waivers from the requisite holders under the
Registration Agreement of the right of all holders to "piggyback" on the
registration statement relating to this offering.
 
     Allegiance, Morgan Stanley & Co. Incorporated, Salomon Brothers Inc, Bear
Stearns & Co. Inc. and Donaldson Lufkin & Jenrette Securities Corporation are
parties to a Warrant Registration Rights Agreement dated as of February 3, 1998.
Allegiance has filed a shelf registration statement with respect to
                                       71
<PAGE>   75
 
the issuance of the common stock issuable upon exercise of the redeemable
warrants; such shelf registration statement was declared effective by the SEC on
March 31, 1999. Allegiance is required to maintain the effectiveness of such
registration statement until all redeemable warrants have expired or been
exercised. Allegiance is required to pay the expenses associated with such
registration. Allegiance has obtained waivers from the holders of a majority of
the warrants of their rights to "piggyback" on the registration statement
relating to this offering.
 
                        SHARES ELIGIBLE FOR FUTURE SALE
 
     After this offering, we will have 62,215,115 shares of common stock
outstanding, excluding 9,426,097 shares reserved for issuance under our stock
plans and 649,248 shares reserved for issuance upon the exercise of outstanding
warrants. All of the shares of common stock sold in this offering will be freely
tradeable under the Securities Act, unless held by our "affiliates," as that
term is defined by the SEC. In addition, 40,341,554 shares of our common stock
have been issued in transactions that were not registered with the SEC and,
thus, are "restricted securities," as that term is defined by the SEC. Upon the
expiration of the lock-up agreements between Allegiance, certain stockholders,
including the selling stockholders, management and the underwriters, these
shares of common stock will become eligible for sale, subject to compliance with
Rule 144 of the Securities Act as described below.
 
     In general, under Rule 144 as currently in effect, a stockholder who has
beneficially owned restricted securities for at least one year, can sell in any
three-month period a number of shares that does not exceed the greater of:
 
     - 1% of the number of shares of common stock then outstanding, or
       approximately 622,151 shares immediately after this offering, or
 
     - the average weekly trading volume of the common stock on the Nasdaq
       National Market during the four calendar weeks immediately preceding the
       date on which such sale is made.
 
     Sales under Rule 144 are subject to certain requirements relating to manner
of sale, notice and availability of current public information about Allegiance.
A stockholder who is not deemed to have been an affiliate at any time during the
90 days immediately preceding the sale and who has beneficially owned restricted
securities for at least two years is entitled to sell such shares under Rule
144(k) without regard to the limitations and requirements described above.
 
     Allegiance, its directors and certain of its officers and certain
stockholders, including the selling stockholders, have agreed with the
underwriters that, for a period of 90 days after the date of this prospectus,
they will not directly or indirectly, offer, pledge, sell, contract to sell,
sell any option or contract to purchase or otherwise dispose of any common stock
or any securities convertible into or exercisable or exchangeable for common
stock, or in any manner transfer all or a portion of the economic consequences
associated with the ownership of the common stock, or cause a registration
statement covering any shares of common stock to be filed, without the prior
written consent of Salomon Smith Barney Inc. and Goldman, Sachs & Co., subject
to certain limited exceptions, including, in the case of Allegiance, the
issuance of shares under the Employee Stock Discount Purchase Plan and 1998
Stock Incentive Plan and grants of options pursuant to, and issuance of shares
upon exercise of options under, the 1997 Nonqualified Stock Option Plan and the
1998 Stock Incentive Plan. See "Management -- Stock Plans." The lock-up
agreements described above may be released at any time as to all or any portion
of the shares subject to such agreements at the sole discretion of Salomon Smith
Barney Inc. and Goldman, Sachs & Co.
 
     Allegiance has filed and will file registration statements on Form S-8
covering the sale of an aggregate of 9,498,970 shares of common stock reserved
for issuance under the 1997 Nonqualified Stock Option Plan, the 1998 Stock
Incentive Plan and the Employee Stock Discount Purchase Plan. See
"Management -- Stock Plans." Accordingly, shares registered under such
registration statement will be available for sale in the public market upon
issuance of such shares pursuant to the respective stock plan, unless such
shares are subject to vesting restrictions and subject to limitations on resale
by "affiliates" pursuant to Rule 144 and under the lock-up agreements described
above.
                                       72
<PAGE>   76
 
     The holders of the warrants are entitled to "piggyback" registration rights
in connection with any public offering of the common stock. In addition,
Allegiance's shelf registration statement with respect to the issuance of the
common stock issuable upon exercise of the warrants was declared effective on
March 31, 1999. Allegiance is required to maintain the effectiveness of such
registration statement until all warrants have expired or been exercised.
 
                                  UNDERWRITING
 
     Subject to the terms and conditions stated in the underwriting agreement
dated the date hereof, each underwriter named below has severally agreed to
purchase, and Allegiance and the selling stockholders have agreed to sell to
such underwriter, the number of shares set forth opposite the name of such
underwriter.
 
<TABLE>
<CAPTION>
                                                              NUMBER OF
                            NAME                                SHARES
                            ----                              ----------
<S>                                                           <C>
Salomon Smith Barney Inc....................................   2,683,200
Goldman, Sachs & Co.........................................   2,683,200
Donaldson, Lufkin & Jenrette Securities Corporation.........   2,683,200
Morgan Stanley & Co. Incorporated...........................   2,683,200
Warburg Dillon Read LLC.....................................   2,683,200
BancBoston Robertson Stephens Inc...........................      90,000
Bear, Stearns & Co. Inc.....................................      90,000
BNY Capital Markets, Inc....................................      90,000
Credit Lyonnais Securities (USA) Inc........................      90,000
Dresdner Kleinwort Benson North America LLC.................      90,000
Paribas Corporation.........................................      90,000
TD Securities (USA) Inc. ...................................      90,000
Brad Peery Inc..............................................      70,000
Doft & Co., Inc.............................................      70,000
First Union Capital Markets Corp............................      70,000
Hoak Breedlove Wesneski & Co................................      70,000
Kaufman Bros., L.P..........................................      70,000
Ladenburg, Thalman & Co. Inc................................      70,000
Legg Mason Wood Walker, Incorporated........................      70,000
Sanders Morris Mundy........................................      70,000
Stifel, Nicolaus & Company, Incorporated....................      70,000
                                                              ----------
          Total.............................................  14,676,000
                                                              ==========
</TABLE>
 
     The underwriting agreement provides that the obligations of the several
underwriters to purchase the shares included in this offering are subject to
approval of certain legal matters by counsel and to certain other conditions.
The underwriters are obligated to purchase all the shares (other than those
covered by the over-allotment option described below) if they purchase any of
the shares.
 
     The underwriters, for whom Salomon Smith Barney Inc., Goldman, Sachs & Co.,
Donaldson, Lufkin & Jenrette Securities Corporation, Morgan Stanley & Co.
Incorporated and Warburg Dillon Read LLC are acting as representatives, propose
to offer some of the shares directly to the public at the public offering price
set forth on the cover page of this prospectus and some of the shares to certain
dealers at the public offering price less a concession not in excess of $.91 per
share. The underwriters may allow, and such dealers may reallow, a concession
not in excess of $.10 per share on sales to certain other dealers. If all of the
shares are not sold at the initial offering price, the representatives may
change the public offering price and the other selling terms.
 
     Allegiance has granted to the underwriters an option, exercisable for 30
days from the date of this prospectus, to purchase up to 2,201,400 additional
shares of common stock at the public offering price less
                                       73
<PAGE>   77
 
the underwriting discount. The underwriters may exercise such option solely for
the purpose of covering over-allotments, if any, in connection with this
offering. To the extent such option is exercised, each underwriter will be
obligated, subject to certain conditions, to purchase a number of additional
shares approximately proportionate to such underwriter's initial purchase
commitment.
 
     In connection with the offering, Allegiance, Allegiance's executive
officers and directors, the selling stockholders, and certain existing
stockholders of Allegiance have agreed that, without the prior written consent
of Salomon Smith Barney Inc. and Goldman, Sachs & Co. on behalf of the
underwriters, they will not:
 
          (a) offer, pledge, sell, contract to sell, sell any option or contract
     to purchase, purchase any option or contract to sell, grant any option,
     right or warrant to purchase, lend or otherwise transfer or dispose of,
     directly or indirectly, any shares of common stock or any securities
     convertible into or exercisable or exchangeable for common stock, or
 
          (b) enter into any swap or similar arrangement that transfers, in
     whole or in part, any of the economic consequences of ownership of the
     common stock,
 
whether any such transaction described in clause (a) or (b) of this paragraph is
to be settled by delivery of such common stock or such other securities, in cash
or otherwise, for a period of 90 days after the date of this prospectus. The
restrictions described in clause (a) and (b) of this paragraph shall not apply
to:
 
          (a) the common stock to be sold in this offering,
 
          (b) the issuance by Allegiance of common stock upon the exercise of an
     option or a warrant or the conversion of a security outstanding on the date
     of this prospectus,
 
          (c) the issuance by Allegiance of additional options to purchase
     shares of common stock pursuant to Allegiance's existing stock option
     plans,
 
          (d) transactions relating to shares of common stock or other
     securities acquired in open market transactions after the completion of
     this offering, and
 
          (e) certain other limited transactions.
 
     The common stock is quoted on the Nasdaq National Market under the symbol
"ALGX."
 
     The following table shows the underwriting discounts and commissions to be
paid to the underwriters by Allegiance in connection with this offering. These
amounts are shown assuming both no exercise and full exercise of the
underwriters' option to purchase additional shares of common stock.
 
<TABLE>
<CAPTION>
                                                                 PAID BY ALLEGIANCE
                                                             ---------------------------
                                                             NO EXERCISE   FULL EXERCISE
                                                             -----------   -------------
<S>                                                          <C>           <C>
Per share..................................................  $      1.52    $      1.52
Total......................................................  $17,975,520    $21,321,648
</TABLE>
 
     In connection with the offering, the underwriters may purchase and sell
shares of common stock in the open market. These transactions may include
over-allotment, syndicate covering transactions and stabilizing transactions.
Over-allotment involves syndicate sales of common stock in excess of the number
of shares to be purchased by the underwriters in the offering, which creates a
syndicate short position. Syndicate covering transactions involve purchases of
the common stock in the open market after the distribution has been completed in
order to cover syndicate short positions. Stabilizing transactions consist of
certain bids or purchases of common stock made for the purpose of preventing or
retarding a decline in the market price of the common stock while the offering
is in progress.
 
     The underwriters also may impose a penalty bid. Penalty bids permit the
underwriters to reclaim a selling concession from a syndicate member when the
underwriters in covering syndicate short positions or making stabilizing
purchases, repurchase shares originally sold by that syndicate member.
 
                                       74
<PAGE>   78
 
     Any of these activities may cause the price of the common stock to be
higher than the price that otherwise would exist in the open market in the
absence of such transactions. These transactions may be effected on the Nasdaq
National Market or in the over-the-counter market, or otherwise and, if
commenced, may be discontinued at any time.
 
     In addition, in connection with this offering, certain of the underwriters
and selling group members may engage in passive market making transactions in
the common stock on the Nasdaq National Market, prior to the pricing and
completion of the offering. Passive market making consists of displaying bids on
the Nasdaq National Market no higher than the bid prices of independent market
makers and making purchases at prices no higher than those independent bids and
effected in response to order flow. Net purchases by a passive market maker on
each day are limited to a specified percentage of the passive market maker's
average daily trading volume in the common stock during a specified period and
must be discontinued when such limit is reached. Passive market making may cause
the price of the common stock to be higher than the price that otherwise would
exist in the open market in the absence of such transactions. If passive market
making is commenced, it may be discontinued at any time.
 
     Allegiance estimates that the total expenses of this offering (excluding
underwriting discounts and commissions) will be $1,100,000.
 
     The representatives have performed certain investment banking and advisory
services for Allegiance from time to time for which they have received customary
fees and expenses. The representatives may, from time to time, engage in
transactions with and perform services for Allegiance in the ordinary course of
their business.
 
     Allegiance and each of the Selling Stockholders have agreed to indemnify
the underwriters against certain liabilities, including liabilities under the
Securities Act of 1933, or to contribute to payments the underwriters may be
required to make in respect of any of those liabilities.
 
     Affiliates of Morgan Stanley & Co. Incorporated and Goldman, Sachs & Co.
are lenders under the revolving credit facility discussed under "Description of
Certain Indebtedness -- Revolving Credit Facility." Affiliates of Morgan Stanley
& Co. Incorporated are significant shareholders of Allegiance and have two
representatives serving on Allegiance's board of directors. See "Principal and
Selling Stockholders" and "Management -- Directors, Executive Officers and Other
Key Employees."
 
                                 LEGAL MATTERS
 
     The validity of the common stock offered hereby will be passed upon for
Allegiance by Kirkland & Ellis (a partnership including professional
corporations), Chicago, Illinois. Certain legal matters will be passed upon for
the underwriters by Shearman & Sterling, New York, New York.
 
                                    EXPERTS
 
     The consolidated balance sheets of Allegiance as of December 31, 1998 and
December 31, 1997, and the related consolidated statements of operations,
stockholders' equity (deficit) and cash flows for the year ended December 31,
1998 and for the period from inception on April 22, 1997 to December 31, 1997,
have been audited by Arthur Andersen LLP, independent public accountants, as
indicated in their report with respect thereto and are included in this
prospectus in reliance upon the authority of said firm as experts in giving said
report.
 
                                       75
<PAGE>   79
 
                      WHERE YOU CAN FIND MORE INFORMATION
 
     We file annual, quarterly and current reports and other information with
the SEC. You may read and copy any document we file at the SEC's public
reference rooms in Washington, D.C., New York, New York, and Chicago, Illinois.
Please call the SEC at 1-800-SEC-0330 for further information on the public
reference rooms. Our SEC filings are also available to the public on the SEC
Internet site at http://www.sec.gov.
 
                                       76
<PAGE>   80
 
                   INDEX TO CONSOLIDATED FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                           <C>
 
Report of Independent Public Accountants....................  F-2
 
Consolidated Balance Sheets as of December 31, 1998, and
  December 31, 1997.........................................  F-3
 
Consolidated Statements of Operations for the year ended
  December 31, 1998, and for the Period from Inception
  (April 22, 1997) through December 31, 1997................  F-4
 
Consolidated Statements of Stockholders' Equity (Deficit)
  for the year ended December 31, 1998, and for the Period
  from Inception (April 22, 1997) through December 31,
  1997......................................................  F-5
 
Consolidated Statements of Cash Flows for the year ended
  December 31, 1998, and for the Period from Inception
  (April 22, 1997) through December 31, 1997................  F-6
 
Notes to Consolidated Financial Statements..................  F-7
</TABLE>
 
                                       F-1
<PAGE>   81
 
                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS
 
To the Board of Directors and Stockholders of Allegiance Telecom, Inc.:
 
     We have audited the accompanying consolidated balance sheets of Allegiance
Telecom, Inc. (a Delaware corporation) and subsidiaries (the "Company") as of
December 31, 1998 and 1997, and the related consolidated statements of
operations, stockholders' equity (deficit), and cash flows for the year ended
December 31, 1998, and for the period from inception (April 22, 1997), to
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 the 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 disclosures 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 Allegiance Telecom, Inc. and
subsidiaries as of December 31, 1998 and 1997, and the results of their
operations and their cash flows for the year ended December 31, 1998, and for
the period from inception (April 22, 1997), to December 31, 1997, in conformity
with generally accepted accounting principles.
 
                                            ARTHUR ANDERSEN LLP
 
Dallas, Texas,
February 3, 1999
 
                                       F-2
<PAGE>   82
 
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           CONSOLIDATED BALANCE SHEETS -- DECEMBER 31, 1998 AND 1997
                (in thousands, except share and per share data)
 
<TABLE>
<CAPTION>
                                                                 1998         1997
                                                              -----------   ---------
<S>                                                           <C>           <C>
                                       ASSETS
CURRENT ASSETS:
  Cash and cash equivalents.................................  $ 262,501.7   $ 5,726.4
  Short-term investments....................................    143,389.7          --
  Short-term investments, restricted........................     25,542.8          --
  Accounts receivable (net of allowance for doubtful
    accounts of $577.2 and $0, at December 31, 1998 and
    1997, respectively).....................................      6,186.6         4.3
  Prepaid expenses and other current assets.................      1,243.2       245.2
                                                              -----------   ---------
        Total current assets................................    438,864.0     5,975.9
PROPERTY AND EQUIPMENT (net of accumulated depreciation and
  amortization of $9,015.4 and $12.7 at December 31, 1998
  and 1997, respectively)...................................    144,860.0    23,899.9
OTHER NONCURRENT ASSETS:
  Deferred debt issuance costs (net of accumulated
    amortization of $733.7 and $0, at December 31, 1998 and
    1997, respectively).....................................     16,078.4          --
  Long-term investments, restricted.........................     36,699.2          --
  Other assets..............................................      1,372.7       171.2
                                                              -----------   ---------
        Total other noncurrent assets.......................     54,150.3       171.2
                                                              -----------   ---------
        Total assets........................................  $ 637,874.3   $30,047.0
                                                              ===========   =========
                   LIABILITIES AND STOCKHOLDERS' EQUITY (DEFICIT)
CURRENT LIABILITIES:
  Accounts payable..........................................  $  20,981.7   $ 2,261.7
  Accrued liabilities and other current liabilities.........     26,176.8     1,668.0
                                                              -----------   ---------
        Total current liabilities...........................     47,158.5     3,929.7
LONG-TERM DEBT..............................................    471,652.1          --
REDEEMABLE CUMULATIVE CONVERTIBLE PREFERRED STOCK,
  $.01 par value, 0 and 40,498,062 shares authorized, 0 and
    40,498,062 shares issued and outstanding at December 31,
    1998 and 1997, respectively.............................           --    33,409.4
REDEEMABLE WARRANTS.........................................      8,634.1          --
COMMITMENTS AND CONTINGENCIES (see Notes 6 and 8)
STOCKHOLDERS' EQUITY (DEFICIT):
  Preferred stock, $.01 par value, 1,000,000 and 0 shares
    authorized, no shares issued or outstanding at December
    31, 1998 and 1997, respectively.........................           --          --
  Common stock, $.01 par value, 150,000,000 and 42,629,965
    shares authorized, 50,341,554 and 426 shares issued and
    outstanding at December 31, 1998 and 1997,
    respectively............................................        503.4          --
  Additional paid-in capital................................    416,729.9     3,008.4
  Deferred compensation.....................................    (14,617.3)   (2,798.4)
  Deferred management ownership allocation charge...........    (26,224.7)         --
  Accumulated deficit.......................................   (265,961.7)   (7,502.1)
                                                              -----------   ---------
        Total stockholders' equity (deficit)................    110,429.6    (7,292.1)
                                                              -----------   ---------
        Total liabilities and stockholders' equity
        (deficit)...........................................  $ 637,874.3   $30,047.0
                                                              ===========   =========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-3
<PAGE>   83
 
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
                     CONSOLIDATED STATEMENTS OF OPERATIONS
                (in thousands, except share and per share data)
 
<TABLE>
<CAPTION>
                                                                                PERIOD FROM
                                                                                 INCEPTION
                                                                             (APRIL 22, 1997),
                                                               YEAR ENDED         THROUGH
                                                              DECEMBER 31,     DECEMBER 31,
                                                                  1998             1997
                                                              ------------   -----------------
<S>                                                           <C>            <C>
REVENUE.....................................................  $   9,786.2       $       0.4
OPERATING EXPENSES:
  Network...................................................      9,528.8             151.2
  Selling, general, and administrative......................     46,089.4           3,425.9
  Management ownership allocation charge....................    167,311.9                --
  Noncash deferred compensation.............................      5,307.2             209.9
  Depreciation and amortization.............................      9,002.8              12.7
                                                              -----------       -----------
          Total operating expenses..........................    237,240.1           3,799.7
                                                              -----------       -----------
          Loss from operations..............................   (227,453.9)         (3,799.3)
OTHER (EXPENSE) INCOME:
  Interest income...........................................     19,917.4             111.4
  Interest expense..........................................    (38,951.7)               --
                                                              -----------       -----------
          Total other (expense) income......................    (19,034.3)            111.4
                                                              -----------       -----------
NET LOSS....................................................   (246,488.2)         (3,687.9)
ACCRETION OF REDEEMABLE PREFERRED STOCK AND WARRANT
  VALUES....................................................    (11,971.4)         (3,814.2)
                                                              -----------       -----------
NET LOSS APPLICABLE TO COMMON STOCK.........................  $(258,459.6)      $  (7,502.1)
                                                              ===========       ===========
NET LOSS PER SHARE, basic and diluted.......................  $    (10.53)      $(17,610.68)
                                                              ===========       ===========
WEIGHTED AVERAGE NUMBER OF SHARES OUTSTANDING, basic and
  diluted...................................................   24,550,346               426
                                                              ===========       ===========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-4
<PAGE>   84
 
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT)
 
                 For the Year Ended December 31, 1998, and for
     the Period from Inception (April 22, 1997), through December 31, 1997
                (in thousands, except share and per share data)
<TABLE>
<CAPTION>
                                                                                                        DEFERRED
                                PREFERRED STOCK         COMMON STOCK                                   MANAGEMENT
                              --------------------   -------------------   ADDITIONAL                   OWNERSHIP
                              NUMBER OF              NUMBER OF              PAID-IN       DEFERRED     ALLOCATION    ACCUMULATED
                               SHARES      AMOUNT      SHARES     AMOUNT    CAPITAL     COMPENSATION     CHARGE        DEFICIT
                              ---------   --------   ----------   ------   ----------   ------------   -----------   -----------
<S>                           <C>         <C>        <C>          <C>      <C>          <C>            <C>           <C>
BALANCE, April 22, 1997
  (date of inception).......        --    $     --           --   $  --    $       --    $       --    $        --   $        --
  Issuance of common stock
    at $.23 per share.......        --          --          426      --           0.1            --             --            --
  Accretion of redeemable
    preferred stock and
    warrant values..........        --          --           --      --            --            --             --      (3,814.2)
  Deferred compensation.....        --          --           --      --       3,008.3      (3,008.3)            --            --
  Amortization of deferred
    compensation............        --          --           --      --            --         209.9             --            --
  Net loss..................        --          --           --      --            --            --             --      (3,687.9)
                               -------    --------   ----------   ------   ----------    ----------    -----------   -----------
BALANCE, December 31,
  1997......................        --          --          426      --       3,008.4      (2,798.4)            --      (7,502.1)
  Accretion of redeemable
    preferred stock and
    warrant values..........        --          --           --      --            --            --             --     (11,971.4)
  Initial public offering...        --          --   10,000,000   100.0     137,656.8            --             --            --
  Conversion of redeemable
    preferred stock.........        --          --   40,341,128   403.4      65,402.0            --             --            --
  Deferred compensation.....        --          --           --      --     210,662.7     (17,126.1)    (193,536.6)           --
  Amortization of deferred
    compensation............        --          --           --      --            --       5,307.2      167,311.9            --
  Net loss..................        --          --           --      --            --            --             --    (246,488.2)
                               -------    --------   ----------   ------   ----------    ----------    -----------   -----------
BALANCE, December 31,
  1998......................        --    $     --   50,341,554   $503.4   $416,729.9    $(14,617.3)   $ (26,224.7)  $(265,961.7)
                               =======    ========   ==========   ======   ==========    ==========    ===========   ===========
 
<CAPTION>
 
                                 TOTAL
                              -----------
<S>                           <C>
BALANCE, April 22, 1997
  (date of inception).......  $        --
  Issuance of common stock
    at $.23 per share.......          0.1
  Accretion of redeemable
    preferred stock and
    warrant values..........     (3,814.2)
  Deferred compensation.....           --
  Amortization of deferred
    compensation............        209.9
  Net loss..................     (3,687.9)
                              -----------
BALANCE, December 31,
  1997......................     (7,292.1)
  Accretion of redeemable
    preferred stock and
    warrant values..........    (11,971.4)
  Initial public offering...    137,756.8
  Conversion of redeemable
    preferred stock.........     65,805.4
  Deferred compensation.....           --
  Amortization of deferred
    compensation............    172,619.1
  Net loss..................   (246,488.2)
                              -----------
BALANCE, December 31,
  1998......................  $ 110,429.6
                              ===========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-5
<PAGE>   85
 
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
                     CONSOLIDATED STATEMENTS OF CASH FLOWS
 
                 For the Year Ended December 31, 1998, and for
     the Period from Inception (April 22, 1997), through December 31, 1997
                                 (in thousands)
 
<TABLE>
<CAPTION>
                                                                 1998          1997
                                                              -----------   ----------
<S>                                                           <C>           <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
  Net loss..................................................  $(246,488.2)  $ (3,687.9)
  Adjustments to reconcile net loss to cash used in
    operating activities --
    Depreciation and amortization...........................      9,002.8         12.7
    Provision for uncollectible accounts receivable.........        577.2           --
    Accretion of senior discount notes......................     27,762.7           --
    Amortization of original issue discount.................        569.9           --
    Amortization of deferred debt issuance costs............        733.7           --
    Amortization of management ownership allocation charge
     and deferred compensation..............................    172,619.1        209.9
    Changes in assets and liabilities --
      Accounts receivable...................................     (6,759.5)        (4.3)
      Prepaid expenses and other current assets.............       (998.0)      (245.2)
      Other assets..........................................     (1,201.5)      (171.2)
      Accounts payable......................................      4,703.9        275.1
      Accrued liabilities and other current liabilities.....     22,208.1      1,668.0
                                                              -----------   ----------
         Net cash used in operating activities..............    (17,269.8)    (1,942.9)
                                                              -----------   ----------
CASH FLOWS FROM INVESTING ACTIVITIES:
  Purchases of property and equipment.......................   (113,538.7)   (21,926.0)
  Purchases of investments..................................   (294,688.8)          --
  Proceeds from redemption of investments...................     89,057.1           --
                                                              -----------   ----------
         Net cash used in investing activities..............   (319,170.4)   (21,926.0)
                                                              -----------   ----------
CASH FLOWS FROM FINANCING ACTIVITIES:
  Proceeds from senior notes................................    443,212.1           --
  Proceeds from issuance of redeemable warrants.............      8,183.5           --
  Deferred debt issuance costs..............................    (16,812.1)          --
  Proceeds from issuance of redeemable preferred stock......           --      5,000.0
  Proceeds from redeemable capital contributions............     20,875.2     24,595.2
  Proceeds from issuance of common stock....................           --          0.1
  Proceeds from initial public offering.....................    137,756.8           --
                                                              -----------   ----------
         Net cash provided by financing activities..........    593,215.5     29,595.3
                                                              -----------   ----------
INCREASE IN CASH AND CASH EQUIVALENTS.......................    256,775.3      5,726.4
CASH AND CASH EQUIVALENTS, beginning of period..............      5,726.4           --
                                                              -----------   ----------
CASH AND CASH EQUIVALENTS, end of period....................  $ 262,501.7   $  5,726.4
                                                              ===========   ==========
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
  Cash paid during the period for --
    Interest................................................  $   9,384.4   $       --
                                                              ===========   ==========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-6
<PAGE>   86
 
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                           DECEMBER 31, 1998 AND 1997
                (in thousands, except share and per share data)
 
1. GENERAL:
 
Allegiance Telecom, Inc., a competitive local exchange carrier (CLEC), was
incorporated on April 22, 1997, as a Delaware corporation, for the purpose of
providing voice, data, and Internet services to business, government, and other
institutional users in major metropolitan areas across the United States.
Allegiance Telecom, Inc. and its subsidiaries are referred to herein as the
"Company."
 
The Company's business plan is focused on offering services in 24 of the largest
metropolitan areas in the United States. As of December 31, 1998, the Company
was operational in nine markets: Atlanta, Boston, Chicago, Dallas, Fort Worth,
Los Angeles, New York City, Oakland and San Francisco and is in the process of
deploying networks in seven other markets: Houston, Northern New Jersey, Orange
County, Philadelphia, San Diego, San Jose and Washington, D.C.
 
Until December 16, 1997, the Company was in the development stage. From its
inception on April 22, 1997, through December 31, 1997, the Company's principal
activities included developing its business plans, procuring governmental
authorizations, raising capital, hiring management and other key personnel,
working on the design and development of its local exchange telephone networks
and operations support systems (OSS), acquiring equipment and facilities, and
negotiating interconnection agreements. Also, the Company initiated resale
services to customers in the Dallas market in December 1997. During 1998, the
Company began providing facilities-based services to customers in its markets.
During 1998, the Company concentrated on building out the markets it is
currently operating in, as well as developing its future markets. Accordingly,
the Company has incurred substantial operating losses and operating cash flow
deficits.
 
The Company's success will be affected by the problems, expenses, and delays
encountered in connection with the formation of any new business and by the
competitive environment in which the Company operates. The Company's performance
will further be affected by its ability to assess potential markets, secure
financing or raise additional capital, implement expanded interconnection and
collocation with incumbent local exchange carrier (ILEC) facilities, lease
adequate trunking capacity from ILECs or other CLECs, purchase and install
switches in additional markets, implement efficient OSS and other back office
systems, develop a sufficient customer base, and attract, retain, and motivate
qualified personnel. The Company's networks and the provisions of
telecommunications services are subject to significant regulation at the
federal, state, and local levels. Delays in receiving required regulatory
approvals or the enactment of new adverse regulation or regulatory requirements
may have a material adverse effect upon the Company. Although management
believes that the Company will be able to successfully mitigate these risks,
there is no assurance that the Company will be able to do so or that the Company
will ever operate profitably.
 
Expenses are expected to exceed revenues in each market in which the Company
offers service until a sufficient customer base is established. It is
anticipated that obtaining a sufficient customer base will take a number of
years, and positive cash flows from operations are not expected in the near
future.
 
2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:
 
CONSOLIDATION
 
The accompanying financial statements include the accounts of Allegiance
Telecom, Inc. and its wholly owned subsidiaries. All significant intercompany
balances and transactions have been eliminated.
 
                                       F-7
<PAGE>   87
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
CASH AND CASH EQUIVALENTS
 
     For purposes of reporting cash flows, the Company includes as cash and cash
equivalents, cash, marketable securities, and commercial paper with original
maturities of three months or less at date of purchase.
 
SHORT-TERM INVESTMENTS
 
     Short-term investments consist primarily of commercial paper with original
maturities at date of purchase beyond three months and less than 12 months. Such
short-term investments are carried at their accreted value, which approximates
fair value, due to the short period of time to maturity.
 
RESTRICTED INVESTMENTS
 
     Restricted investments consist primarily of U.S. government securities
purchased in connection with the Company's outstanding 12 7/8% Notes (see Note
4) to secure the first three years' (six semiannual) interest payments on the
12 7/8% Notes. Such investments are stated at their accreted value, which
approximates fair value, and are shown in both current and other noncurrent
assets, based upon the maturity dates of each of the securities at the balance
sheet date.
 
     Restricted investments also includes $787.2 in certificates of deposit held
as collateral for letters of credit issued on behalf of the Company. These
investments are classified as other noncurrent assets.
 
ACCOUNTS RECEIVABLE
 
     Accounts receivable consist of end-user receivables, interest receivable,
and at December 31, 1997, a receivable from an employee.
 
PREPAID EXPENSES AND OTHER CURRENT ASSETS
 
     Prepaid expenses and other current assets consist of prepaid rent, prepaid
insurance, and refundable deposits. Prepayments are expensed on a straight-line
basis over the life of the underlying agreements.
 
PROPERTY AND EQUIPMENT
 
     Property and equipment includes network equipment, leasehold improvements,
software, office equipment, furniture and fixtures, construction-in-progress,
and other. These assets are stated at cost, which includes direct costs and
capitalized interest, and are depreciated once placed in service using the
straight-line method. Interest expense for the year ended December 31, 1998, was
$41,749.9 before the capitalization of $2,798.2 of interest related to
construction-in-progress. No interest expense was incurred during the period
ended December 31, 1997. Repair and maintenance costs are expensed as incurred.
 
                                       F-8
<PAGE>   88
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     Property and equipment at December 31, 1998 and 1997, consist of the
following:
 
<TABLE>
<CAPTION>
                                                                                   USEFUL
                                                                                   LIVES
                                                           1998        1997      (IN YEARS)
                                                        ----------   ---------   ----------
<S>                                                     <C>          <C>         <C>
Network equipment.....................................  $ 67,303.8   $      --       5-7
Leasehold improvements................................    24,483.2        37.5      5-10
Software..............................................     7,840.0          --         3
Office equipment and other............................     4,384.3        89.9         2
Furniture and fixtures................................     2,419.6       150.2         5
                                                        ----------   ---------
Property and equipment, in service....................   106,430.9       277.6
Less -- accumulated depreciation......................    (9,015.4)      (12.7)
                                                        ----------   ---------
Property and equipment, in service, net...............    97,415.5       264.9
Construction-in-progress..............................    47,444.5    23,635.0
                                                        ----------   ---------
Property and equipment, net...........................  $144,860.0   $23,899.9
                                                        ==========   =========
</TABLE>
 
REVENUE RECOGNITION
 
     Revenue is recognized in the month in which the service is provided, except
for reciprocal compensation generated by calls placed to Internet service
providers connected to the Company's network. The propriety of CLECs (such as
the Company) to earn local reciprocal compensation is the subject of numerous
regulatory and legal challenges. Until this issue is ultimately resolved, the
Company has determined to recognize this revenue only when realization of it is
certain, which in most cases will be upon receipt of cash.
 
COMPREHENSIVE INCOME
 
     In June 1997, the Financial Accounting Standards Board (FASB) issued
Statement of Financial Accounting Standards (SFAS) No. 130 (SFAS 130),
"Reporting Comprehensive Income." SFAS 130 established reporting and disclosure
requirements for comprehensive income and its components within the financial
statements. The Company's comprehensive income components were immaterial as of
December 31, 1998, and the Company had no comprehensive income components as of
December 31, 1997; therefore, comprehensive income/loss is the same as net
income/loss for both periods.
 
LOSS PER SHARE
 
     The Company calculates net loss per share under the provisions of SFAS No.
128, "Earnings per Share." The net loss per share amounts reflected on the
statements of operations and the number of shares outstanding on the balance
sheets reflect a 426.2953905-for-one stock split, which occurred in connection
with the initial public offering (see Note 3). The net loss applicable to common
stock includes the accretion of redeemable cumulative convertible preferred
stock and warrant values of $11,971.4 for the year ended December 31, 1998, and
$3,814.2 for the period from inception (April 22, 1997), through December 31,
1997.
 
                                       F-9
<PAGE>   89
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     The securities listed below were not included in the computation of diluted
loss per share, since the effect from the conversion would be antidilutive.
 
<TABLE>
<CAPTION>
                                                                   DECEMBER 31,
                                                              ----------------------
                                                                1998        1997
                                                              --------   -----------
<S>                                                           <C>        <C>
Redeemable Cumulative Convertible Preferred Stock...........        --    40,498,062
Redeemable Warrants.........................................   649,248            --
1997 Nonqualified Stock Option Plan.........................   886,127       189,127
1998 Stock Incentive Plan...................................   365,526            --
Employee Stock Discount Purchase Plan.......................    44,624            --
</TABLE>
 
RECOGNITION OF THE COST OF START-UP ACTIVITIES
 
     On April 3, 1998, the American Institute of Certified Public Accountants
issued Statement of Position No. 98-5 (SOP 98-5), "Reporting on the Costs of
Start-up Activities." SOP 98-5 requires that start-up activities and
organization costs be expensed as incurred and that start-up costs capitalized
prior to the adoption of SOP 98-5 be reported as a cumulative effect of a change
in accounting principle. The Company adopted SOP 98-5 during the second quarter
of 1998. Adoption of SOP 98-5 did not have an effect on the Company, inasmuch as
the Company had previously expensed all such costs.
 
ACCOUNTING FOR DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES
 
     In June 1998, the FASB issued SFAS No. 133, "Accounting for Derivative
Instruments and Hedging Activities" (SFAS 133). SFAS 133 requires that all
derivatives be recognized at fair value as either assets or liabilities. SFAS
133 also requires an entity that elects to apply hedge accounting to establish
the method to be used in assessing the effectiveness of the hedging derivatives
and the measurement approach for determining the ineffectiveness of the hedge at
the inception of the hedge. The methods chosen must be consistent with the
entity's approach to managing risk. The Company adopted SFAS 133 at the
beginning of the fourth quarter of 1998. Adoption of SFAS 133 did not have an
effect on the Company, inasmuch as the Company has historically not invested in
derivatives or participated in hedging activities.
 
USE OF ESTIMATES IN FINANCIAL STATEMENTS
 
     The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of expenses during the reporting period.
Actual results could differ from those estimates.
 
RECLASSIFICATIONS
 
     Certain amounts in the prior period's consolidated financial statements
have been reclassified to conform with the current period presentation.
 
3. CAPITALIZATION:
 
     In connection with its initial public offering of common stock (the "IPO")
on July 7, 1998 (see below), the Company effected a 426.2953905-for-one stock
split, which is retroactively reflected within these financial statements.
 
                                      F-10
<PAGE>   90
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
STOCK PURCHASE AGREEMENT AND SECURITY HOLDERS AGREEMENT
 
     On August 13, 1997, the Company entered into a stock purchase agreement
with Allegiance Telecom, LLC ("Allegiance LLC") (see Note 7). Allegiance LLC
purchased 40,498,062 shares of 12% redeemable cumulative convertible preferred
stock ("Redeemable Preferred Stock"), par value $.01 per share, for aggregate
consideration of $5,000.0 (the "Initial Closing"). Allegiance LLC agreed to make
additional contributions as necessary to fund expansion into new markets
("Subsequent Closings"). In order to obtain funds through Subsequent Closings,
the Company submitted a proposal to Allegiance LLC detailing the funds necessary
to build out the Company's business in a new market. Allegiance LLC was not
required to make any contributions until it approved the proposal. The maximum
commitment of Allegiance LLC was $100,000.0. No capital contributions were
required to be made after the Company consummated an initial public offering of
its stock (which occurred on July 7, 1998).
 
     Allegiance LLC contributed a total of $50,132.9 and $29,595.2 prior to the
Company's initial public offering and as of December 31, 1997, respectively.
Each security holder in Allegiance LLC had the right to require Allegiance LLC
to repurchase all of the outstanding securities held by such security holder at
the greater of the original cost (including interest at 12% per annum) for such
security or the fair market value, as defined in the security holders agreement,
at any time and from time to time after August 13, 2004, but not after the
consummation of a public offering or sale of the Company. If repurchase
provisions had been exercised, the Company had agreed, at the request and
direction of Allegiance LLC, to take any and all actions necessary, including
declaring and paying dividends and repurchasing preferred or common stock, to
enable Allegiance LLC to satisfy its repurchase obligations.
 
     Because of the redemption provisions, the Company has recognized the
accretion of the value of the Redeemable Preferred Stock to reflect management's
estimate of the potential future fair market value of the Redeemable Preferred
Stock payable in the event the repurchase provisions were exercised. Amounts
were accreted using the effective interest method, assuming the Redeemable
Preferred Stock is redeemed at a redemption price based on the estimated
potential future fair market value of the equity of the Company in August 2004.
The accretion was recorded each period as an increase in the balance of
Redeemable Preferred Stock outstanding and a noncash increase in the net loss
applicable to common stock.
 
     In connection with the IPO, the Redeemable Preferred Stock was converted
into common stock, and the amounts accreted were reclassified as a component of
additional paid-in capital. In addition, the redemption provisions and the
obligation of Allegiance LLC to make additional contributions to the Company
(and the obligation of the members of Allegiance LLC to make capital
contributions) have terminated.
 
REDEEMABLE CUMULATIVE CONVERTIBLE PREFERRED STOCK
 
     Each share of the Company's Redeemable Preferred Stock was convertible into
shares of the Company's common stock (the "Common Stock") on a one-for-one
basis, subject to certain antidilution provisions. No dividends were declared in
1998 or 1997.
 
     In 1998, prior to the conversion of the Redeemable Preferred Stock, the
Company recorded accretion of $11,520.8. Accretion recorded in the period ended
December 31, 1997, was $3,814.2.
 
     Capital contributed in the Subsequent Closings occurring in October 1997
and January 1998 and other capital contributions totaled approximately
$45,132.9.
 
     In February and March 1998, the Company issued 273,361.92 shares of
Redeemable Preferred Stock for aggregate consideration of $337.5.
 
                                      F-11
<PAGE>   91
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     In connection with the consummation of the IPO, the outstanding shares of
the Redeemable Preferred Stock were converted into 40,341,128 shares of Common
Stock. Upon the conversion of the Redeemable Preferred Stock, the obligation of
the Company to redeem the Redeemable Preferred Stock also terminated and,
therefore, the accretion of the Redeemable Preferred Stock value recorded to the
date of the IPO, $15,335.0, was reclassified to additional paid-in capital along
with $50,470.4 proceeds from the issuance of the Redeemable Preferred Stock and
redeemable capital contributions.
 
PREFERRED STOCK
 
     In connection with the IPO, the Company authorized 1,000,000 shares of
preferred stock ("Preferred Stock") with a $.01 par value. At December 31, 1998,
no shares of Preferred Stock were issued and outstanding.
 
COMMON STOCK
 
     On July 7, 1998, the Company raised $150,000.0 of gross proceeds in the
Company's IPO. The Company sold 10,000,000 shares of its Common Stock at a price
of $15 per share. In connection with the IPO, the outstanding shares of
Redeemable Preferred Stock were converted in to 40,341,128 shares of Common
Stock, and the Company increased the number of authorized Common Stock to
150,000,000. At December 31, 1998, 50,341,554 shares were issued and
outstanding. Of the authorized but unissued Common Stock, 6,998,970 shares are
reserved for issuance upon exercise of options issued under the Company's stock
option, stock incentive, and stock purchase plans (see Note 10) and 649,248
shares are reserved for issuance, sale, and delivery upon the exercise of
warrants (see Note 4).
 
DEFERRED COMPENSATION
 
     Allegiance LLC sold to certain management investors (the "Management
Investors") membership units of Allegiance LLC at amounts less than their
estimated fair market value; therefore, the Company has recognized deferred
compensation of $10,090.2 and $977.6 at December 31, 1998 and 1997,
respectively, of which $2,726.1 and $40.7 have been amortized to expense at
December 31, 1998 and 1997, respectively. In connection with the IPO, the
Redeemable Preferred Stock was converted into Common Stock, and Allegiance LLC
was dissolved. The deferred compensation charge is amortized based upon the
period over which the Company has the right to repurchase certain of the
securities (at the lower of fair market value or the price paid by the employee)
in the event the management employee's employment with the Company is
terminated.
 
DEFERRED MANAGEMENT OWNERSHIP ALLOCATION CHARGE
 
     On July 7, 1998, in connection with the IPO, certain venture capital
investors (the "Fund Investors") and certain Management Investors owned 95.0%
and 5.0%, respectively, of the ownership interests of Allegiance LLC, which
owned substantially all of the Company's outstanding capital stock. As a result
of the successful IPO, Allegiance LLC was dissolved, and its assets (which
consisted almost entirely of such capital stock) have been distributed to the
Fund Investors and Management Investors in accordance with Allegiance LLC's
Limited Liability Company Agreement (the "LLC Agreement"). The LLC Agreement
provided that the equity allocation between the Fund Investors and the
Management Investors be 66.7% and 33.3%, respectively, based upon the valuation
implied by the IPO. Under generally accepted accounting principles, the Company
recorded the increase in the assets of Allegiance LLC allocated to the
Management Investors as a $193,536.6 increase in additional paid-in capital, of
which $122,475.5 was recorded as a noncash, nonrecurring charge to operating
expense and $71,061.1 was recorded as a deferred management ownership allocation
charge. The deferred charge was amortized at $44,836.4 as of December 31, 1998,
and will be further amortized at $18,870.2, $7,175.7, and $178.8 during the
years
 
                                      F-12
<PAGE>   92
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
1999, 2000, and 2001, respectively, which is the period over which the Company
has the right to repurchase certain of the securities (at the lower of fair
market value or the price paid by the employee) in the event the management
employee's employment with the Company is terminated.
 
4. LONG-TERM DEBT:
 
     Long-term debt consisted of the following:
 
<TABLE>
<CAPTION>
                                                                  DECEMBER 31,
                                                              --------------------
                                                                 1998       1997
                                                              ----------   -------
<S>                                                           <C>          <C>
Series B 11 3/4% Notes, face amount $445,000.0 due February
  15, 2008, effective interest rate of 12.45%, at accreted
  value.....................................................  $270,526.1   $    --
12 7/8% Senior Notes, face amount $205,000.0 due May 15,
  2008, effective interest rate of 13.24%, at accreted
  value.....................................................   201,018.6
Other.......................................................       107.4        --
                                                              ----------   -------
          Total long-term debt..............................  $471,652.1   $    --
                                                              ==========   =======
</TABLE>
 
     On February 3, 1998, the Company raised gross proceeds of approximately
$250,477.1 in an offering of 445,000 Units (the "Unit Offering"), each of which
consists of one 11 3/4% Senior Discount Note due 2008 of the Company (the
"11 3/4% Notes") and one warrant to purchase .0034224719 shares of Common Stock
(the "Redeemable Warrants") at an exercise price of $.01 per share, subject to
certain antidilution provisions. Of the gross proceeds, $242,293.6 was allocated
to the 11 3/4% Notes and $8,183.5 was allocated to the Redeemable Warrants. The
Redeemable Warrants became exercisable in connection with the IPO (see Note 3)
in July 1998, and each warrant may now purchase 1.45898399509 shares of Common
Stock as a result of the stock split (see Note 3).
 
     A Registration Statement on Form S-4 (File No. 333-49013), registering the
Company's 11 3/4% Notes and offering to exchange (the "Exchange Offer") any and
all of the outstanding 11 3/4% Notes for Series B 11 3/4% Notes due 2008 (the
"Series B Notes"), was declared effective by the Securities and Exchange
Commission on May 22, 1998. The Exchange Offer terminated after all of the
outstanding 11 3/4% Notes were exchanged. The terms and conditions of the Series
B Notes are identical to those of the 11 3/4% Notes in all material respects.
 
     The Series B Notes have a principal amount at maturity of $445,000.0 and an
effective interest rate of 12.45%. The Series B Notes mature on February 15,
2008. From and after February 15, 2003, interest on the Series B Notes will be
payable semiannually in cash at the rate of 11 3/4% per annum.
 
     The Company must make an offer to purchase the Redeemable Warrants for cash
at the relevant value upon the occurrence of a repurchase event. A repurchase
event is defined to occur when (i) the Company consolidates with or merges into
another person if the Common Stock thereafter issuable upon exercise of the
Redeemable Warrants is not registered under the Securities Exchange Act of 1934,
as amended (the "Exchange Act") or (ii) the Company sells all or substantially
all of its assets to another person, if the Common Stock thereafter issuable
upon the exercise of the Redeemable Warrants is not registered under the
Exchange Act, unless the consideration for such a transaction is cash. The
relevant value is defined to be the fair market value of the Common Stock as
determined by the trading value of the securities if publicly traded or at an
estimated fair market value without giving effect to any discount for lack of
liquidity, lack of registered securities, or the fact that the securities
represent a minority of the total shares outstanding. As a result of the warrant
redemption provisions, the Company is recognizing the potential future
redemption value of the Redeemable Warrants by recording accretion of the
Redeemable
 
                                      F-13
<PAGE>   93
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
Warrants to their estimated fair market value at February 3, 2008, using the
effective interest method. Accretion recorded in the year ended December 31,
1998, was $450.6.
 
     The Series B Notes are redeemable by the Company, in whole or in part,
anytime on or after February 15, 2003, at 105.875% of their principal amount at
maturity, plus accrued and unpaid interest, declining to 100% of their principal
amount at maturity, plus accrued and unpaid interest on and after February 15,
2006. In addition, at any time prior to February 15, 2001, the Company may, at
its option, redeem up to 35% of the principal amount at maturity of the Series B
Notes in connection with one or more public equity offerings at 111.750% of the
accreted value on the redemption date, provided that at least $289,250.0
aggregate principal amount at maturity of the Series B Notes remains outstanding
after such redemption.
 
     On July 7, 1998, the Company raised approximately $200,918.5 of gross
proceeds from the sale of its 12 7/8% Senior Notes due 2008 (the "12 7/8%
Notes"), of which approximately $69,033.4 was used to purchase U.S. government
securities, which were placed in a pledged account to secure and fund the first
six scheduled payments of interest on the notes (see Note 2).
 
     The 12 7/8% Notes have a principal amount at maturity of $205,000.0 and an
effective interest rate of 13.24%. The 12 7/8% Notes mature on May 15, 2008.
Interest on the 12 7/8% Notes is payable semiannually in cash at the rate of
12 7/8% on May 15 and November 15 of each year. As of December 31, 1998, the
Company has recorded accrued interest associated with the 12 7/8% Notes of
$3,470.2, which is included in other current liabilities.
 
     The 12 7/8% Notes are redeemable by the Company, in whole or in part, at
any time on or after May 15, 2003, at 106.438% of their principal amount,
declining to 100% of their principal amount, plus accrued interest, on or after
May 15, 2006. In addition, prior to May 15, 2001, the Company may redeem up to
35% of the aggregate principal amount of the 12 7/8% Notes with the proceeds of
one or more public offerings (as defined in the indenture relating to the
12 7/8% Notes) at 112.875% of their principal amount, plus accrued interest,
provided, however, that after any such redemption at least 65% of the aggregate
principal amount of the 12 7/8% Notes originally issued remains outstanding.
 
     The Series B and the 12 7/8% Notes carry certain restrictive covenants
that, among other things, limit the ability of the Company to incur
indebtedness, create liens, engage in sale-leaseback transactions, pay dividends
or make distributions in respect to their capital stock, redeem capital stock,
make investments or certain other restricted payments, sell assets, issue or
sell stock of restricted subsidiaries (as defined in the indentures relating to
the Series B Notes and the 12 7/8% Notes), enter into transactions with any
holder of 5% or more of any class of capital stock of the Company, or effect a
consolidation or merger. In addition, upon a change of control, the Company is
required to make an offer to purchase each series of notes at a purchase price
of 101% of the accreted value thereof (in the case of the Series B Notes) and
101% of the principal amount thereof (in the case of the 12 7/8% Notes),
together with accrued interest, if any. However, these limitations are subject
to a number of qualifications and exceptions (as defined in the indentures
relating to each series of notes). The Company was in compliance with all such
restrictive covenants of each series of notes at December 31, 1998.
 
5. CAPITAL LEASES:
 
     On May 29, 1998, the Company signed a capital lease agreement for three,
four-fiber rings, with a term of 10 years and a renewal term of 10 years, at an
expected total cost of $3,485.0; $871.3 was paid as of December 31, 1998. The
remainder is expected to be paid in 1999 and is not reflected in the financial
statements, since the payment is contingent upon the timing of completion of
network segments.
 
                                      F-14
<PAGE>   94
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     On December 4, 1998, the Company signed a capital lease agreement for 12
optical fibers configured in two separate rings, with a term of 15 years and two
renewal terms of five years each. Total cost associated with the capital lease
is dependent upon the timing of completion of connectivity of the optical fibers
with the Company's network, which is to be completed in two phases. The Company
will incur recurring monthly charges of $29.4 after the completion of phase one.
After completion of phase two, the Company will pay a one-time fee of $76.5 and
the recurring monthly charge will increase to $76.5. This capital lease is not
reflected in the financial statements, since the total cost and timing of
payments are contingent upon the timing of completion of the phases.
 
6. LEGAL MATTERS:
 
     On August 29, 1997, WorldCom, Inc. ("WorldCom") sued the Company and two
individual employees. In its complaint, WorldCom alleges that these employees
violated certain noncompete and nonsolicitation agreements by accepting
employment with the Company and by soliciting then-current WorldCom employees to
leave WorldCom's employment and join the Company. In addition, WorldCom claims
that the Company tortiously interfered with WorldCom's relationships with its
employees and that the Company's behavior constituted unfair competition.
WorldCom seeks injunctive relief and damages, although it has filed no motion
for a temporary restraining order or preliminary injunction. The Company denies
all claims and will vigorously defend itself. An estimate of possible loss
cannot be made at this time.
 
     On October 7, 1997, the Company filed a counterclaim against WorldCom for,
among other things, attempted monopolization of the "one-stop shopping"
telecommunications market, abuse of process, and unfair competition. WorldCom
moved to dismiss the abuse of process and unfair competition claims. The court
dismissed the unfair competition claim on March 4, 1998. Thus, the Company's
counterclaim for attempted monopolization and abuse of power are still being
litigated.
 
7. RELATED PARTIES:
 
     From inception (April 22, 1997) through July 7, 1998, the Company was a
wholly owned subsidiary of Allegiance LLC. On July 7, 1998, the Fund Investors
and the Management Investors owned 95.0% and 5.0%, respectively, of the
ownership interest of Allegiance LLC, which owned substantially all of the
Company's outstanding capital stock. As a result of the successful IPO (see Note
3), Allegiance LLC was dissolved, and its assets (which consisted almost
entirely of such capital stock) have been distributed to the Fund Investors and
the Management Investors in accordance with the LLC Agreement (see Note 3).
 
     As of July 7, 1998 and 1997, Allegiance LLC had made aggregate capital
contributions to the Company of approximately $50,132.9 and $29,595.2,
respectively.
 
     During 1998 and 1997, the Company paid all organizational and legal fees of
Allegiance LLC, the amount of which was not material. No amounts are due from
Allegiance LLC at December 31, 1998, or December 31, 1997.
 
     In connection with the Unit Offering (see Note 4), the IPO (see Note 3),
and the sale of the 12 7/8% Notes (see Note 4), the Company incurred
approximately $11,331.5 in fees to an affiliate of an investor in the Company.
 
                                      F-15
<PAGE>   95
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
8. COMMITMENTS AND CONTINGENCIES:
 
     The Company has entered into various operating lease agreements, with
expirations through 2009, for network facilities, office space, and equipment.
Future minimum lease obligations related to the Company's operating leases as of
December 31, 1998, are as follows:
 
<TABLE>
<S>                                            <C>
1999........................................   $10,984.8
2000........................................    11,201.6
2001........................................    10,436.7
2002........................................     8,600.8
2003........................................     7,940.7
Thereafter..................................    30,083.5
</TABLE>
 
     Total rent expense for the year ended December 31, 1998, was $2,991.8 and
for the period from inception (April 22, 1997) through December 31, 1997, was
$212.1.
 
     In October 1997, the Company entered into a five-year general agreement
with Lucent Technologies, Inc. ("Lucent") establishing terms and conditions for
the purchase of Lucent products, services, and licensed materials. This
agreement includes a three-year exclusivity commitment for the purchase of
products and services related to new switches. The agreement contains no minimum
purchase requirements.
 
9. FEDERAL INCOME TAXES:
 
     The Company accounts for income tax under the provisions of SFAS No. 109,
"Accounting for Income Taxes" (SFAS 109). SFAS 109 requires an asset and
liability approach that requires the recognition of deferred tax assets and
liabilities for the expected future tax consequences of events that have been
recognized in the Company's financial statements. The Company had approximately
$53,572.5 and $460.5 of net operating loss carryforwards for federal income tax
purposes at December 31, 1998 and 1997, respectively. The net operating loss
carryforwards will expire in the years 2012 and 2018 if not previously utilized.
The Company has recorded a valuation allowance equal to the net deferred tax
assets at December 31, 1998 and 1997, due to the uncertainty of future operating
results. The valuation allowance will be reduced at such time as management
believes it is more likely than not that the net deferred tax assets will be
realized. Any reductions in the valuation allowance will reduce future
provisions for income tax expense.
 
     The Company's deferred tax assets and liabilities and the changes in those
assets are:
 
<TABLE>
<CAPTION>
                                                         1997        CHANGE        1998
                                                       ---------   ----------   ----------
<S>                                                    <C>         <C>          <C>
Start-up costs capitalized for tax purposes..........  $ 1,025.9   $   (213.7)  $    812.2
Net operating loss carryforward......................      156.6     18,058.1     18,214.7
Amortization of original issue discount..............         --      9,663.6      9,663.6
Depreciation.........................................         --     (2,392.4)    (2,392.4)
Valuation allowance..................................   (1,182.5)   (25,115.6)   (26,298.1)
                                                       ---------   ----------   ----------
                                                       $      --   $       --   $       --
                                                       =========   ==========   ==========
</TABLE>
 
     Amortization of the original issue discount on the Series B Notes and
12 7/8% Notes as interest expense is not deductible in the income tax return
until paid.
 
                                      F-16
<PAGE>   96
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     Under existing income tax law, all operating expenses incurred prior to a
company commencing its principal operations are capitalized and amortized over a
five-year period for tax purposes.
 
10. STOCK OPTION/STOCK INCENTIVE/STOCK PURCHASE PLANS:
 
     At December 31, 1998, the Company had three stock-based compensation plans:
the 1997 Nonqualified Stock Option Plan (the "1997 Option Plan"), the 1998 Stock
Incentive Plan, and the Employee Stock Discount Purchase Plan (the "Stock
Purchase Plan"). The Company applies the provisions of Accounting Principles
Board Opinion No. 25, "Accounting for Stock Issued to Employees," and the
related interpretations in accounting for the Company's plans. Had compensation
cost for the Company's plans been determined based on the fair value of the
options as of the grant dates for awards under the plans, consistent with the
method prescribed in SFAS No. 123, "Accounting for Stock-Based Compensation,"
the Company's net loss applicable to common stock and net loss per share would
have increased to the pro forma amounts indicated below. The Company utilized
the following assumptions in calculating the estimated fair value of each option
on the date of grant, using the Black-Scholes option-pricing model with the
following weighted-average assumptions for grants in 1998 and 1997: dividend
yield of 0%, expected volatility of 89.1%, and expected lives of six years for
both years: risk-free interest rates of 5.63% in 1998 and 6.06% in 1997 for the
1997 Option Plan and 4.70% in 1998 for the 1998 Stock Incentive Plan.
 
<TABLE>
<CAPTION>
                                                                 1998         1997
                                                              ----------   ----------
<S>                                                           <C>          <C>
Net loss applicable to common stock -- as reported..........  $258,459.6   $  7,502.1
Net loss applicable to common stock -- pro forma............   259,796.6      7,512.2
Net loss per share, basic and diluted -- as reported........       10.53    17,610.68
Net loss per share, basic and diluted -- pro forma..........       10.58    17,634.27
</TABLE>
 
     As the 1998 Stock Incentive Plan and the Stock Purchase Plan were adopted
in 1998, the December 31, 1997, pro forma balances do not include expenses for
these plans.
 
1997 OPTION PLAN AND 1998 STOCK INCENTIVE PLAN
 
     Under the 1997 Option Plan, the Company granted options to key employees, a
director, and a consultant of the Company for an aggregate of 1,037,474 shares
of the Company's Common Stock. The Company will not grant options for any
additional shares under the 1997 Option Plan.
 
     Under the 1998 Stock Incentive Plan, the Company may grant options to
certain employees, directors, advisors, and consultants of the Company. The 1998
Stock Incentive Plan provides for issuance of the following types of incentive
awards: stock options, stock appreciation rights, restricted stock, performance
grants, and other types of awards that the Compensation Committee of the Board
of Directors (the "Compensation Committee") deems consistent with the purposes
of the 1998 Stock Incentive Plan. The Company has reserved 3,655,778 shares of
Common Stock for issuance under the 1998 Stock Incentive Plan.
 
     Options granted under both plans have a term of six years and vest over a
three-year period, and the Compensation Committee administers both option plans.
 
                                      F-17
<PAGE>   97
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     A summary of the status of the 1997 Option Plan as of December 31, 1998 and
1997, is presented in the table below:
 
<TABLE>
<CAPTION>
                                           DECEMBER 31, 1998            DECEMBER 31, 1997
                                      ---------------------------   --------------------------
                                                 WEIGHTED AVERAGE             WEIGHTED AVERAGE
                                       SHARES     EXERCISE PRICE    SHARES     EXERCISE PRICE
                                      --------   ----------------   -------   ----------------
<S>                                   <C>        <C>                <C>       <C>
Outstanding, beginning of period....   189,127        $2.47              --        $  --
Granted.............................   848,347         2.76         189,127         2.47
Exercised...........................        --           --              --           --
Forfeited...........................  (151,347)        2.60              --           --
                                      --------                      -------
Outstanding, end of period..........   886,127         2.73         189,127         2.47
                                      ========                      =======
Options exercisable at period-end...    44,481                           --
                                      ========                      =======
Weighted average fair value of
  options granted...................  $   2.82                      $  0.68
                                      ========                      =======
</TABLE>
 
     As of December 31, 1998 and 1997, options outstanding under the 1997 Option
Plan have a weighted average remaining contractual life of 5.2 and 5.8 years,
respectively.
 
     A summary of the status of the 1998 Stock Incentive Plan as of December 31,
1998, is presented in the table below:
 
<TABLE>
<CAPTION>
                                                                   DECEMBER 31, 1998
                                                              ----------------------------
                                                                          WEIGHTED AVERAGE
                                                               SHARES      EXERCISE PRICE
                                                              ---------   ----------------
<S>                                                           <C>         <C>
Outstanding, beginning of period............................         --        $   --
Granted.....................................................    399,974         10.21
Exercised...................................................         --            --
Forfeited...................................................    (34,448)        10.47
                                                              ---------
Outstanding, end of period..................................    365,526         10.19
                                                              =========
Options exercisable at period-end...........................         --
                                                              =========
Weighted average fair value of options granted..............  $   10.22
                                                              =========
</TABLE>
 
     As of December 31, 1998, options outstanding under the 1998 Stock Incentive
Plan have a weighted average remaining contractual life of 5.7 years.
 
     As the estimated fair market value of the Company's Common Stock (as
implied by the IPO price) exceeded the exercise price of the options granted,
the Company has recognized deferred compensation of $7,635.0 and $2,030.7 at
December 31, 1998 and 1997, respectively, of which $2,581.1 and $169.2 have been
amortized to expense at December 31, 1998 and 1997, respectively, over the
vesting period of the options. As of December 31, 1998, the Company has reversed
$599.1 of unamortized deferred compensation related to options forfeited.
 
                                      F-18
<PAGE>   98
                   ALLEGIANCE TELECOM, INC. AND SUBSIDIARIES
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
STOCK PURCHASE PLAN
 
     The Company's Stock Purchase Plan is intended to give employees a
convenient means of purchasing shares of Common Stock through payroll
deductions. Each participating employee's contributions will be used to purchase
shares for the employee's share account as promptly as practicable after each
calendar quarter. The cost per share will be 85% of the lower of the closing
price of the Company's Common Stock on the Nasdaq National Market on the first
or the last day of the calendar quarter. The Company has reserved 2,305,718
shares of Common Stock for issuance under the Stock Purchase Plan. As of
December 31, 1998, no shares have been issued under the Stock Purchase Plan;
however, participants have contributed $303.4 and will be issued 44,624 shares
of Common Stock in January 1999. The Compensation Committee administers the
Stock Purchase Plan.
 
                                      F-19
<PAGE>   99
 
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                               14,676,000 SHARES
 
                            ALLEGIANCE TELECOM, INC.
 
                                  COMMON STOCK
 
                        [ALLEGIANCE TELECOM, INC., LOGO]
 
                                  ------------
 
                                   PROSPECTUS
                                 APRIL 14, 1999
 
                                  ------------
 
                              SALOMON SMITH BARNEY
 
                              GOLDMAN, SACHS & CO.
 
                          DONALDSON, LUFKIN & JENRETTE
 
                           MORGAN STANLEY DEAN WITTER
 
                            WARBURG DILLON READ LLC
 
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