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Registration No. 333-      

SECURITIES AND EXCHANGE COMMISSION

FORM S-4

NM ACQUISITION CORP.

With copies to:

    Approximate date of commencement of proposed sale of securities to the public: At the effective time of the merger of NEXTLINK Communications, Inc. and Concentric Network Corporation with and into Registrant, which shall occur as soon as practicable after the effective date of this Registration Statement and the satisfaction of or waiver of all conditions to the closing of such merger.

    If the securities being registered on this form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box: [   ]

    If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration number of the earlier effective registration statement for the same offering. [   ]

    If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the effective registration statement for the same offering. [   ]

CALCULATION OF REGISTRATION FEE

	(i)	with respect to the class A common stock, in accordance with Rule 457(f)(1), based on the average of the high and low sale prices for shares of common stock of Concentric Network corporation and class A common stock of NEXTLINK Communications, Inc. on the Nasdaq NMS on April 14, 2000:

	(a)	Concentric common stock, 57,344,762 shares, multiplied by average price, $43.00 plus
	(b)	NEXTLINK class A common stock, 87,879,042 shares, multiplied by average price, $88.05; and

	(ii)	with respect to the class B common stock of NEXTLINK, in accordance with Rule  457(f)(2), based on the par value per share: NEXTLINK Class B common stock, 59,880,765 shares, multiplied by par value per share $0.02.

(3)	Shares of the Registrant’s class A common stock expected to be issued in the transactions described herein to holders of Concentric common stock.
(4)	Shares of the Registrant’s class A common stock expected to be issued in the transactions described herein to holders of NEXTLINK class A common stock.
(5)	Shares of the Registrant’s class B common stock expected to be issued in the transactions described herein to holders of NEXTLINK class B common stock.

     The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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[CONCENTRIC LOGO]

To Our Stockholders:

      I am pleased to announce the proposed merger with NEXTLINK Communications, Inc. This merger will create a combined company offering a broad set of solutions for telecommunications and Internet services.

      The merger is structured so that Concentric and NEXTLINK will merge into a third company, named NM Acquisition Corp., which has been formed for this purpose and which, following the merger, will be known as NEXTLINK Communications, Inc. This merger is described in detail in the attached document.

      In the merger, if the average trading price of NEXTLINK common stock is between $69.23 and $90.91 per share, then for each share of Concentric common stock you hold, you will receive common stock of the combined company worth $45 per share. Holders of Concentric common stock will receive a higher amount if the average trading price of NEXTLINK common stock is higher than $90.91 per share, and will receive a lower amount if the average trading price of NEXTLINK common stock is lower than $69.23 per share. For a more detailed discussion, please see the section entitled “Questions and Answers About the Merger” beginning inside on page iv.

      You will be asked to vote upon the merger agreement and the merger with NEXTLINK at a special meeting of Concentric stockholders. The date, time and place of this special meeting is:

          ,             , 2000

      The merger cannot be consummated unless the holders of a majority of shares of Concentric common stock approve the merger agreement and the merger. Only stockholders who hold shares of Concentric common stock at the close of business on           , 2000, the record date, will be entitled to vote at the special meeting.

      We are very excited by the opportunities we see for the combined company. After careful consideration, your board of directors has unanimously determined that the terms and conditions of the merger are fair to and in the best interests of you, the Concentric stockholders, and has recommended that you approve the merger agreement and merger.

      Please carefully read this document for detailed information about NEXTLINK, the combined company and the merger. Your vote is very important regardless of the number of shares you own. Whether or not you expect to attend the special meeting, please mark, date, sign and promptly return the accompanying proxy in the enclosed postage-prepaid envelope, so that your shares may be represented at the special meeting. Returning your proxy does not deprive you of your right to attend the special meeting and vote your shares in person.

	Very truly yours,
	Henry R. Nothhaft
	Chairman, President and
	Chief Executive Officer

      Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved the securities to be issued under this proxy statement/information statement/prospectus or passed upon the adequacy or accuracy of this proxy statement/information statement/prospectus. Any representation to the contrary is a criminal offense.

      This proxy statement/information statement/prospectus is dated           , 2000 and is first being mailed to Concentric stockholders on or about           , 2000

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[CONCENTRIC LOGO]

CONCENTRIC NETWORK CORPORATION

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

To Our Stockholders:

      Notice is hereby given that a special meeting of stockholders of Concentric Network Corporation will be held on                , 2000  at       a.m., Pacific Daylight Time, at the principal executive offices of Concentric at 1400 Parkmoor Avenue, San Jose, California 95126-3429, for the following purpose:

      To consider and vote upon a proposal to adopt the Agreement and Plan of Merger and Share Exchange Agreement, dated as of January 9, 2000, by and among Concentric, NEXTLINK Communications, Inc., Eagle River Investments, L.L.C. and NM Acquisition Corp., and to approve the acquisition of Concentric by NEXTLINK by means of a merger of both Concentric and NEXTLINK into NM Acquisition Corp., a company formed for this purpose. We describe the merger and the merger agreement more fully in the accompanying proxy statement/information statement/prospectus, which we urge you to read. This document is also a prospectus of NM Acquisition Corp. relating to the shares of NM Acquisition Corp. common stock to be issued in the merger, and an information statement for the stockholders of NEXTLINK.

      Only existing stockholders of record of Concentric common stock at the close of business on           , 2000 are entitled to vote at the special meeting or any adjournments or postponements of the special meeting. YOUR VOTE IS VERY IMPORTANT. Approval of the merger proposal, requires the favorable vote of the holders of a majority of the outstanding shares of Concentric common stock. A FAILURE BY A HOLDER OF CONCENTRIC COMMON STOCK TO VOTE, EITHER BY NOT RETURNING THE ENCLOSED PROXY OR BY CHECKING THE “ABSTAIN” BOX ON THE PROXY, WILL HAVE THE SAME EFFECT AS A VOTE AGAINST THE MERGER.

      Please mark, date, sign and promptly return your proxy whether or not you plan to attend the special meeting.

      The board of directors of Concentric has unanimously approved the merger and the merger agreement and determined that the merger is advisable and in the best interests of Concentric and its stockholders. After careful consideration, the Concentric board of directors unanimously recommends that the Concentric stockholders vote “FOR” the proposal.

	By Order of the Board of
	Directors
	Henry R. Nothhaft
	Chairman, President and
	Chief Executive Officer

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[NEXTLINK LOGO]

Dear NEXTLINK Stockholder:

      The board of directors of NEXTLINK Communications, Inc. has approved the merger of NEXTLINK and Concentric Network Corporation. In the merger, among other things, NEXTLINK and Concentric will each merge with and into NM Acquisition Corp., a Delaware corporation without any operations or material assets which was formed in connection with the merger and which, following the merger, will change its name to NEXTLINK Communications, Inc.

      Eagle River Investments, L.L.C., which owns shares representing more than 50% of the total voting power of all outstanding NEXTLINK common stock, agreed in connection with the execution of the merger agreement to approve the merger and did so on                     , 2000. Under Delaware law and the terms of NEXTLINK’s certificate of incorporation and bylaws, Eagle River’s approval is sufficient to approve the merger and the merger agreement. For this reason, NEXTLINK is not calling a meeting of its stockholders to vote on the merger and the merger agreement. WE ARE NOT ASKING YOU FOR A PROXY AND YOU ARE REQUESTED NOT TO SEND US A PROXY.

      Although we are not asking you for a proxy and ask that you not send us one, we are furnishing this information statement in order to provide you with important information about the merger. Please read this document and the attached merger agreement carefully. This document is also a prospectus of NM Acquisition Corp. relating to the shares of NM Acquisition Corp. common stock to be issued in the merger, and a proxy statement for the stockholders of Concentric who are being asked to approve the merger.

      This proxy statement/information statement/prospectus constitutes notice to the holders of NEXTLINK class B common stock of stockholder action taken, pursuant to a written consent and notice of appraisal rights pursuant to Section 202 of the Delaware General Corporation Law.

Daniel F. Akerson,

      Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved the securities to be issued under this proxy statement/information statement/prospectus or passed upon the adequacy or accuracy of this proxy statement/information statement/prospectus. Any representation to the contrary is a criminal offense.

      This proxy statement/information statement/prospectus is dated           , 2000 and is first being mailed to NEXTLINK stockholders on or about           , 2000.

SUBJECT TO COMPLETION. DATED APRIL 17, 2000

PRELIMINARY PROXY STATEMENT/ INFORMATION STATEMENT/ PROSPECTUS

PROSPECTUS OF

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      This proxy statement/ information statement/ prospectus incorporates important business and financial information about Concentric and NEXTLINK that is not included or delivered with this document. This business and financial information is available without charge to stockholders of both Concentric and NEXTLINK upon their written or oral request at the following address and/or telephone number:

      For Concentric stockholders:

	CONCENTRIC NETWORK CORPORATION
	1400 Parkmoor Avenue
	San Jose, CA 95126
	Attention: Investor Relations
	Telephone number: (408) 817-2000

      For NEXTLINK stockholders:

	NEXTLINK COMMUNICATIONS, INC.
	1505 Farm Credit Drive, 6th Floor
	McLean, VA 22102
	Attention: Investor Relations
	Telephone number: (703) 547-2000

If you would like to request documents from Concentric or NEXTLINK and want to receive them prior to the Concentric stockholder meeting, please make your request at least five business days before the date of that meeting, or             , 2000.

See also “Where You Can Find More Information” on page 77.

      NM Acquisition Corp. may not sell the securities to be issued under this prospectus until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell securities and it is not soliciting an offer to buy securities in any state where the offer or sale is not permitted.

      In this proxy statement/ information statement/ prospectus, unless otherwise indicated, “we” refers to both Concentric and NEXTLINK, and “our” refers to both Concentric and NEXTLINK.

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QUESTIONS AND ANSWERS ABOUT THE MERGER

Q:	What will NEXTLINK stockholders receive in the merger?

A:	NEXTLINK stockholders will receive one share of NM Acquisition Corp. class A common stock for each share of NEXTLINK class A common stock and one share of NM Acquisition Corp. class B common stock for each share of NEXTLINK class B common stock.

Q:	What is NM Acquisition Corp. and what will its stock represent?

A:

NM Acquisition Corp. is a newly-formed corporation which will have no assets and liabilities of its own until the closing of the merger. After the closing, its assets and business will be those of NEXTLINK and Concentric, and it will also own 100% of INTERNEXT, L.L.C., a Delaware limited liability company. NEXTLINK will be contributing the majority of the assets of NM Acquisition Corp., and NEXTLINK stockholders will receive NM Acquisition Corp. shares on a one-for-one basis as discussed above.

Q:	What is the difference between NM Acquisition Corp. class A and class B common stock?

A:

NM Acquisition Corp. class A common stock, which holders of Concentric common stock and NEXTLINK class A common stock will receive in the merger, will be entitled to one vote per share. NM Acquisition Corp. class B common stock, which holders of NEXTLINK class B common stock will receive in the merger, will be entitled to ten votes per share and will be convertible on a one-for-one basis into shares of NM Acquisition Corp. class A common stock. These differences are identical to the differences between NEXTLINK’s class A common stock and class B common stock. Except for these differences, NM  Acquisition Corp. class A class common stock and class B common stock will be identical.

Q:	What will Concentric stockholders receive in the Merger?

A:

For each share of Concentric common stock converted in the merger, Concentric stockholders will receive NM Acquisition Corp. class A common stock worth $45 dollars per share, unless the average price of NEXTLINK common stock prior to the merger is less than $69.23 per share or more than $90.91 per share. This type of range is called a “collar.” Each share of NM Acquisition Corp. class A common stock is intended to be the economic equivalent of a share of NEXTLINK common stock.

Q:	How does the collar work?

A:

If the NEXTLINK share price is within the collar, the exchange ratio adjusts between 0.495 and 0.650 so that Concentric stockholders receive class A common stock of NM Acquisition Corp. with a value (based on the value of an equivalent number of NEXTLINK shares) of $45 per share of Concentric common stock. If the NEXTLINK share price is outside the collar, the exchange ratio is fixed (at 0.495 if the NEXTLINK average share price is higher than $90.91 per share and at 0.650 if it is less than $69.23 per share), and the value of the merger consideration will depend upon the value of the underlying NEXTLINK shares. If the average NEXTLINK share price is below the low end of the collar, Concentric stockholders will receive NM Acquisition Corp. common stock worth less than $45 per share for each share of Concentric common stock converted in the merger. If the average NEXTLINK share price is above the high end of the collar, Concentric stockholders will receive NM Acquisition Corp. class A common stock worth more than $45 per share for each share of Concentric common stock converted in the merger.

Q:	How is the average NEXTLINK share price computed?

A:	It’s the volume-weighted average price on the Nasdaq National Market, as reported by Bloomberg, L.P., for the 20 trading day period ending on the third trading day prior to the closing of the merger.

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Q:	Does the board of directors of Concentric recommend voting in favor of the merger agreement and the merger?

A:	Yes. After careful consideration, the board of directors of Concentric has determined that the merger is in the best interest of Concentric and its stockholders, has unanimously approved the merger agreement and the merger, and recommends that its stockholders vote in favor of the merger agreement and the merger.

Q:	Has the NEXTLINK board of directors approved the merger agreement and the merger?

A:	Yes. After careful consideration, the board of directors of NEXTLINK has determined that the merger is in the best interest of NEXTLINK and its stockholders and has unanimously approved the merger agreement and the merger.

Q:	Should Concentric stockholders send in stock certificates now?

A:	No. After we complete the merger, NM Acquisition Corp. (which will then be renamed NEXTLINK Communications, Inc.) will send instructions to Concentric stockholders explaining how to exchange their certificates for shares of Concentric common stock.

Q:	Will NEXTLINK stockholders need to send stock certificates now or later?

A:	No. Shares of NEXTLINK common stock will, by operation of the merger, be deemed to be converted into shares of NM Acquisition Corp. common stock, and there will be no need for NEXTLINK stockholders to exchange their common stock certificates.

Q:	What do I need to do now?

A:

Please carefully read and consider the information contained in this proxy statement/information statement/prospectus. If you are a Concentric stockholder, you may indicate how you want to vote on your proxy card and then sign and mail your proxy card in the enclosed return envelope as soon as possible so that your shares will be represented at the Concentric special meeting. You may also attend the special meeting and vote in person instead of submitting a proxy.

Q:	What if I don’t vote?

A:

If you are a Concentric stockholder and you fail either to return your proxy card or to vote in person at the special meeting, or if you mark your proxy “abstain,” the effect will be a vote against the merger agreement and the merger. If you sign and send in your proxy without indicating how you want to vote, your proxy will be counted as a vote for the merger agreement and the merger unless your shares are held in a brokerage account.

Q:	If my shares are held in a brokerage account, will my broker vote my shares for me?

A:

If you are a Concentric stockholder, your broker will not be able to vote your shares without instructions from you on how to vote. Therefore, it is important that you follow the directions provided by your broker regarding how to instruct your broker to vote your shares. If you fail to provide your broker with instructions, it will have the same effect as a vote against the merger agreement and the merger.

Q:	May I change my vote after I have mailed in my signed proxy card?

A:

If you are a Concentric stockholder, you may change your vote at any time before the vote takes place at the Concentric special meeting. To do so, you may either complete and submit a later dated proxy card or send a written notice stating that you would like to revoke your proxy. In addition, you may attend the special meeting and vote in person. However, if you elect to vote in person at the special meeting and your shares are held by a broker, bank or other nominee, you must bring to the special meeting a letter from the broker, bank or other nominee confirming your beneficial ownership of the shares.

Q:	When do you expect to complete the merger?

A:	We are working to complete the merger in the second quarter of 2000, as soon as practicable after Concentric stockholder approval is obtained at the Concentric special meeting. Because the merger is subject to other conditions, however, we cannot predict the exact timing.

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Q:	When and where is the Concentric special meeting?

A:	The special meeting of Concentric stockholders will be held on             , 2000, at      a.m., Pacific Daylight Time, at the principal executive offices of Concentric at 1400 Parkmoor Avenue, San Jose, California 95126-3429.

Q:	What are the federal income tax consequences of the merger?

A:

The merger is intended to qualify as a tax-free reorganization under the Internal Revenue Code. Accordingly, no gain or loss will generally be recognized by Concentric, NEXTLINK or NM Acquisition Corp. as a result of the merger. Additionally, no gain or loss will be recognized by Concentric or NEXTLINK stockholders to the extent they receive shares of NM Acquisition Corp. common stock in the merger. In general, however, Concentric stockholders will recognize taxable gain to the extent they receive cash in lieu of fractional shares in the merger. Concentric stockholders should consult their tax advisors for a full understanding of the tax consequences of the merger.

Q:	Are there any risks associated with the merger?

A:	Yes. The merger does involve some risks. For a discussion of risk factors that should be considered in evaluating the merger, see “Risk Factors” on page 13.

Q:	Who can I contact with questions?

A:	If you are a Concentric stockholder and you have questions about the merger or how to submit your proxy, you should contact:

If you are a NEXTLINK stockholder and you have questions about the merger you should contact:

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SUMMARY

      This brief summary does not contain all of the information about the merger that may be important to you. You should read this entire document and the other documents we refer to for a more complete understanding of NEXTLINK, Concentric and the terms of the merger. See “Where You Can Find More Information” beginning on page 77.

The Companies

NEXTLINK COMMUNICATIONS, INC.

      Since 1996, NEXTLINK has provided high quality telecommunications services to the rapidly growing business market. To serve its customers’ broad and expanding telecommunications needs, NEXTLINK has assembled a unique collection of high-bandwidth, local and national network assets. These assets include:

	•	31 high-bandwidth, or broadband, local networks operating in 19 states, generally located in the central business districts of the cities NEXTLINK serves, the number of which is increasing as NEXTLINK continues to build additional networks;
	•	high-capacity fixed broadband spectrum covering 95% of the population of the 30 largest U.S. cities; and
	•	an interest in a national fiber optic network now being built for INTERNEXT, L.L.C. that will connect over 50 cities in the United States and Canada, including all of the major metropolitan markets that NEXTLINK’s current and planned local networks serve. NEXTLINK currently holds a 50% interest in INTERNEXT, L.L.C., but has agreed to acquire the remaining 50% interest in conjunction with the merger.

      NEXTLINK intends to integrate these assets with additional communications technologies and services in order to become one of the nation’s leading providers of a comprehensive array of communications services.

      NEXTLINK now operates 31 broadband local networks in 49 cities, providing nearly 428,000 business telephone lines to its customers as of December 31, 1999, of which more than 78,000 were installed in the fourth quarter of 1999. NEXTLINK is currently building additional networks, and plans to have operational networks in most of the 30 largest U.S. cities by the end of 2000.

      For further information on NEXTLINK, see “Where You Can Find More Information” on page 77.

CONCENTRIC NETWORK CORPORATION

      Since 1995, Concentric has provided tailored, Internet-protocol based network services for small to medium sized companies. Concentric provides these services through data centers connected to its national network, which forms a part of the Internet backbone. Concentric’s services include implementing private networks for companies, offering high speed access to the Internet, and hosting Web-sites on the World Wide Web.

      By using Concentric’s services, companies can take advantage of Internet tools, such as browsers and high performance servers, to customize their data communications both within a company and between a company and its suppliers, partners and customers. Concentric’s services incorporate the advantages of a public network, such as low cost, nationwide access and standard protocols, with the advantages of a private network, such as customization, high performance, reliability and security. Concentric’s current distribution partners include Intuit, SBC and Web TV.

      For further information on Concentric, see “Where You Can Find More Information” on page 77.

NM ACQUISITION CORP.

      NM Acquisition Corp. was incorporated in Delaware on December 13, 1999. NM Acquisition Corp. does not have, and will not have prior to completion of the merger, any operations, assets or liabilities. Other than the shares of NM Acquisition Corp. issued in the LHP share exchange immediately prior to the

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      NM Acquisition Corp. will be treated as the successor entity to NEXTLINK for all reporting purposes under U.S. securities laws.

The Merger (see page 29)

      In the merger, Concentric and NEXTLINK will each merge with and into NM Acquisition Corp. As a result of the merger, the separate existence of Concentric and NEXTLINK will cease and NM Acquisition Corp. will succeed to the business, assets and liabilities of Concentric and NEXTLINK. Immediately following the merger, NM Acquisition Corp. will change its name to NEXTLINK Communications, Inc.

      For a detailed description of the terms of the merger, see “The Merger” beginning on page 29.

Concentric Special Meeting (see page 26)

      The Concentric special meeting will be held on           , 2000 at           a.m. Pacific Daylight Time, at the principal executive offices of Concentric at 1400 Parkmoor Avenue, San Jose, California. At the special meeting or any adjournment of the special meeting, Concentric stockholders will be asked to consider and vote upon a proposal to approve the merger and the merger agreement.

      Concentric stockholders are entitled to cast one vote per share of Concentric common stock owned as of the close of business on        , 2000, the record date for determining Concentric stockholders entitled to vote at the Concentric special meeting. There were             shares of Concentric common stock outstanding on the record date.

Stockholder Votes Required to Approve the Merger (see page 28)

  Concentric

      The affirmative vote of the holders of a majority of the outstanding shares of Concentric common stock is required to approve and adopt the merger agreement and approve the merger. The failure by a holder of Concentric common stock to vote or instruct a broker, bank or other record holder on how to vote (if that holder’s shares are held in street name) will have the effect of a vote against the merger agreement and the merger. As of the record date, there were                      shares of Concentric common stock entitled to vote outstanding. Concentric’s directors, executive officers and their affiliates hold        % of the outstanding shares entitled to vote, as of the record date.

  NEXTLINK

      The votes of a majority of the total voting power of the outstanding shares of NEXTLINK common stock are required to approve and adopt the merger agreement and approve the merger. Eagle River Investments, L.L.C., which owns shares representing more than 50% of the total voting power of all outstanding NEXTLINK common stock, agreed in connection with the execution of the merger agreement to approve the merger and did so on                     , 2000. As of the record date, there were                      shares entitled to vote outstanding. NEXTLINK’s directors, executive officers and their affiliates hold        % of the outstanding shares of NEXTLINK common stock entitled to vote, as of the record date. Under Delaware law and the terms of NEXTLINK’s certificate of incorporation and bylaws, Eagle River’s approval will be sufficient to approve the merger and the merger agreement. For this reason, NEXTLINK is not calling a meeting of its stockholders to vote on the merger and the merger agreement, nor is NEXTLINK asking its stockholders for a proxy.

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Board Approvals and Recommendations

  Concentric

      The board of directors of Concentric believes that the merger agreement is fair to, and in the best interests of, the stockholders of Concentric, and has unanimously approved the merger and the merger agreement. The Concentric board unanimously recommends that Concentric stockholders vote “FOR” the approval of the merger agreement and the merger.

  NEXTLINK

      The board of directors of NEXTLINK believes that the merger agreement is fair to, and in the best interests of, the stockholders of NEXTLINK, and has approved the merger and the merger agreement. The board of directors of NEXTLINK established a special committee to give independent consideration to the LHP share exchange (which is described below in this summary and in “The Merger Agreement and Related Agreements — LHP Share Exchange”), and the special committee evaluated and participated in the negotiation of the LHP share exchange. The special committee unanimously determined that the LHP share exchange, as contemplated by the merger agreement, is fair to and in the best interests of the NEXTLINK and recommended that the board of directors of NEXTLINK approve the LHP share exchange.

Reasons for the Merger (see page 31-34)

      The boards of directors of Concentric and NEXTLINK believe that the merger may result in a number of benefits to Concentric’s and NEXTLINK’s stockholders, including, among other potential benefits:

	•	the combined company is expected to compete more effectively in the rapidly growing market for telecommunications and Internet services;
	•	the merger may provide the combined company with greater depth of skilled personnel, strengthened research and development activity and expanded distribution and support capacity;
	•	customers of both companies would have access to expanded telecommunications and other products and services;
	•	the merger may provide the combined company with access to each company’s existing customer base and partners; and
	•	the creation of a larger customer base, a higher market profile and greater financial strength would present greater opportunities for marketing the products and services of the combined company.

      In addition, the Concentric board of directors believes that the merger may result in a number of benefits to Concentric and its stockholders, including, among other potential benefits:

	•	opportunities after combining Concentric’s business with NEXTLINK’s business, compared with the opportunities for Concentric as a stand-alone company;
	•	alignment of interests, goals and objectives resulting from a broadened communications business, allowing the combined company to leverage synergies resulting from an integrated management team, streamlined operation, and strengthened infrastructure;
	•	the ability to combine NEXTLINK’s growing local telephone service business and its existing and planned long distance and fixed wireless network assets with Concentric’s web hosting and Internet data services, enabling the combined company to provide cross selling opportunities and other synergies;
	•	potential synergies of the combined company, including the offering of a complete, single-source communications service for small and medium-sized businesses, consisting of Concentric’s Internet business, data center and application service provider services, transported across NEXTLINK’s network;

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	•	access to NEXTLINK’s planned Internet Protocol (IP)-centric national fiber optic network and extensive fixed wireless spectrum;
	•	the continued consolidation of the network services communications industry which enables businesses with substantial resources to effectively compete in the future in cost structure and service offerings; and
	•	the opportunity for Concentric stockholders to participate in the potential for growth of the combined company’s business after the merger, in the form of the combined company’s common stock.

      In addition, the NEXTLINK board of directors believes that the merger may result in a number of benefits to NEXTLINK and its stockholders, including, among other potential benefits:

	•	acceleration of NEXTLINK’s planned expansion of its data product and service offerings;
	•	the opportunity to increase revenue relating to the utilization of NEXTLINK’s network assets;
	•	the opportunity to move local and data traffic onto NEXTLINK’s broadband metropolitan and broadband wireless networks; and
	•	access to an established base in the European data marketplace.

      To review the background and reasons for the merger in greater detail, as well as the risks of the merger, see “The Merger— Concentric’s Reasons for the Merger and Additional Considerations” beginning on page 31, “— NEXTLINK’s Reasons for the Merger and Additional Considerations” beginning on page 33, “— Background of the Merger” beginning on page 29, “— Opinion of Concentric’s Financial Advisor” beginning on page 34, “— Opinion of NEXTLINK’s Financial Advisor” beginning on page 43 and “Risk Factors — Risks Related to the Merger” beginning on page 13.

Opinions of Financial Advisors (see pages 34 and 43; Appendices B and C)

      In deciding to approve the merger and the merger agreement, the board of directors of Concentric considered the opinion of its financial advisor and the board of directors of NEXTLINK considered the opinion of its financial advisor. Concentric received an opinion from its financial advisor, Bear, Stearns & Co. Inc., that the exchange ratio was fair, from a financial point of view, to the Concentric stockholders. NEXTLINK received an opinion from its financial advisor, Merrill Lynch & Co., that the exchange ratio was fair from a financial point of view to NEXTLINK.

Interests of Insiders of Concentric in the Merger (see page 49)

      When considering the recommendation of the Concentric board, you should be aware that the terms of the merger agreement and agreements it contemplates gives a number of Concentric executive officers and key employees substantial interests in the merger that are different from, or in addition to, the interests of Concentric stockholders, including stock option grants at market exercise prices, shares of restricted stock and cash retention bonuses. The board of directors of Concentric was aware of these interests at the time it adopted the merger agreement and approved the merger.

Overview of the Merger Agreement (see page 58)

      For a detailed description of the merger agreement see “The Merger Agreement and Related Agreements” beginning on page 58. The merger agreement is attached to the back of this proxy statement/information statement prospectus as Appendix A.

Conditions to the Merger

      Concentric and NEXTLINK will complete the merger only if Concentric’s stockholders approve it and other contractual and other legal conditions are either satisfied or waived.

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Limitation on Negotiations

      Until the merger is completed or the merger agreement terminated, Concentric has agreed not to directly or indirectly solicit other acquisition proposals and to notify NEXTLINK promptly of any third party inquiries or requests for non-public information that could lead to an acquisition proposal.

Termination of the Merger Agreement

      Either Concentric or NEXTLINK may terminate the merger agreement if, among other things:

	•	the merger is not completed on or before August 31, 2000; or
	•	Concentric accepts or recommends to its stockholders a superior proposal and pays to NEXTLINK a $110 million termination fee.

      Concentric does not have any right to terminate the merger agreement solely because the price of NEXTLINK common stock declines, even though the exchange rate on conversion will not be adjusted to maintain a $45 value if NEXTLINK’s share price falls below $69.23 per share. However, Concentric and NEXTLINK may agree at any time not to complete the merger, even if Concentric’s stockholders have approved it.

Termination Fees and Expenses

      Concentric has agreed to pay NEXTLINK a termination fee of $110 million upon the occurrence of certain events. Otherwise, Concentric and NEXTLINK will generally pay their own fees and expenses in connection with the merger, whether or not the merger is completed.

Amendment of the Merger Agreement

      Concentric and NEXTLINK may jointly amend the terms of the merger agreement. However, after Concentric’s stockholders approve the merger, any amendment which changes the amount or form of consideration in the merger would require further stockholder approval.

LHP Share Exchange

      Currently, NEXTLINK and Eagle River Investments, L.L.C. each own 50% of LHP, L.L.C., a Washington limited liability company, which in turn owns 100% of INTERNEXT, whose sole asset is an interest in a national telecommunications network currently under construction. Immediately prior to the merger, Eagle River or its controlling affiliate will contribute 100% of the outstanding equity interests in LHP to NM Acquisition Corp. in exchange for approximately 3.4 million shares of NM Acquisition Corp. class A common stock. As a result, NM Acquisition Corp. will own 100% of both LHP and INTERNEXT.

Accounting Treatment

      The merger of Concentric and NEXTLINK will be accounted for as a purchase of the Concentric business by NEXTLINK. The LHP share exchange will be accounted for on an historical cost basis, since NEXTLINK and INTERNEXT are under common control.

Completion and Effectiveness of the Merger

      We will complete the merger when all of the conditions for completion of the merger are satisfied or waived in accordance with the merger agreement. The merger will become effective when we file certificates of merger with the State of Delaware. We expect to complete the merger during the second quarter of 2000.

Appraisal Rights (see page 53)

      Under Delaware law, Concentric common stockholders and NEXTLINK class A common stockholders are not entitled to appraisal rights in connection with the merger. However, holders of NEXTLINK class B

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Material Federal Income Tax Consequences (see page 54)

      The merger is intended to qualify as a “reorganization” for United States federal income tax purposes. In general, therefore, the Concentric stockholders and the NEXTLINK stockholders, respectively, will recognize no gain or loss upon the exchange of shares of Concentric common stock and NEXTLINK common stock, respectively, for NM Acquisition Corp. common stock in the merger, except to the extent of cash received in lieu of fractional shares.

      The obligation of Concentric and NEXTLINK to consummate the merger is subject to the prior receipt of an opinion from Wilson Sonsini Goodrich & Rosati, counsel to Concentric, and an opinion from Willkie Farr & Gallagher, counsel to NEXTLINK, that the merger will be treated as a “reorganization” within the meaning of the Internal Revenue Code, and that each of Concentric, NEXTLINK and NM Acquisition Corp. will be a party to the reorganization within the meaning of Section 368(b) of the Internal Revenue Code for United States federal income tax purposes. For a further discussion of the tax consequences of the merger, see “The Merger — Material Federal Income Tax Consequences of the Merger.”

Listing of NM Acquisition Corp. Class A Common Stock (see page 57)

      Prior to the effective time, NM Acquisition Corp. will list the shares of its common stock to be delivered in the merger on The Nasdaq National Market.

Concentric Voting Agreements (see page 64)

      To induce NEXTLINK to enter into the merger agreement, ten Concentric officers and directors holding approximately   % of Concentric’s common stock outstanding at the record date have agreed with NEXTLINK to vote their Concentric shares in favor of the merger and the adoption of the merger agreement and against approval of any proposal opposing or competing against the merger.

Required Regulatory Approvals (see page 61)

      The obligations of Concentric and NEXTLINK to consummate the merger is conditioned upon the receipt of regulatory approvals. NEXTLINK is required to obtain, and is in the process of obtaining, the approval of eleven state public utility service commissions to the merger of NEXTLINK with and into NM Acquisition Corp.

Officers and Directors After the Merger (see page 66)

      After the merger, the NM Acquisition Corp. board of directors will consist of the current NEXTLINK board of directors, with the addition of Henry Nothhaft, President, Chief Executive Officer and Chairman of the Board of Concentric, and Peter C. Waal, currently a member of the board of directors of Concentric. The officers of NEXTLINK immediately prior to the consummation of the merger will be the officers of NM Acquisition Corp. following consummation of the merger, with the addition of Mr. Nothhaft as Vice Chairman and other officers of Concentric.

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MARKET PRICE INFORMATION

      Concentric common stock trades on The Nasdaq National Market under the symbol “CNCX.” NEXTLINK class A common stock trades on The Nasdaq National Market under the symbol “NXLK.” The following table presents the quarterly high and low sales prices for each of Concentric common stock and NEXTLINK class A common stock as reported on The Nasdaq National Market for the periods indicated. Concentric common stock commenced trading on July 31, 1997 and NEXTLINK common stock commenced trading on September 26, 1997. NEXTLINK 1998 and 1999 prices have been adjusted for the two-for-one stock split effected August 27, 1999.

Recent Closing Prices

      On January 7, 2000, the last trading day before announcement of the proposed merger, the closing prices per share of common stock of Concentric and class A common stock of NEXTLINK on The Nasdaq National Market were as follows:

      On        , 2000, the latest practicable trading day before the printing of this proxy statement/information statement/prospectus, the closing prices per share of each of Concentric common stock and NEXTLINK common stock on The Nasdaq National Market were as follows:

      We urge you to obtain current market quotations for Concentric common stock and NEXTLINK common stock. We cannot give you any assurances as to the future prices or markets for Concentric common stock or NEXTLINK common stock. Stockholders can call 800 [       ] toll free in order to obtain information regarding the current exchange ratio.

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SELECTED FINANCIAL DATA OF CONCENTRIC

      The following is a summary of consolidated financial information regarding Concentric’s financial position and operating results as of the dates and for the periods indicated. This information is only a summary and you should read it in conjunction with the financial statements and other information Concentric has filed with the Securities and Exchange Commission. You should read this summary in conjunction with “Management’s Discussion and Analysis of Financial Conditions and Results of Operations” included in Concentric’s 1999 Form 10-K, which explains and qualifies it. See “Where You Can Find More Information” on page 77.

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SELECTED FINANCIAL DATA OF NEXTLINK

      The following is a summary of consolidated financial information regarding NEXTLINK’s financial position and operating results as of the dates and for the periods indicated. This information is only a summary and you should read it in conjunction with the financial statements and other information NEXTLINK has filed with the Securities and Exchange Commission. You should read this summary in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in NEXTLINK’s 1999 Form 10-K, which explains and qualifies it. See “Where You Can Find More Information” on page 77.

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NEXTLINK and Concentric Pro Forma Condensed Combined

      The following selected unaudited pro forma condensed combined financial data of NEXTLINK and Concentric combine the consolidated financial information of NEXTLINK for the year ended December 31, 1999 and the year ended December 31, 1998, with the consolidated financial information of Concentric for the year ended December 31, 1999, and the year ended December 31, 1998. The selected unaudited pro forma condensed combined financial data are derived from the unaudited pro forma combined condensed financial statements contained elsewhere in this proxy statement. We have prepared the unaudited pro forma condensed combined financial information using the purchase method of accounting. This pro forma information does not give effects to any restructuring costs or to any potential cost savings or other operating efficiencies that could result from the merger.

      The unaudited pro format condensed combined financial information does not purport to represent what the combined company’s financial position or results of operations would have been had the merger occurred at the beginning of the earliest period presented or to project the combined financial position or results of operations for any future date or period.

      You should read the financial information in this section along with historical and unaudited pro forma condensed combined financial statements and accompanying notes, either incorporated by reference or included in this proxy statement. See “Unaudited Pro Forma Condensed Combined Financial Statements” beginning on page 68.

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COMPARATIVE PER SHARE DATA

      You should read the comparative share data presented below in conjunction with the historical financial statements and related notes contained in the annual and other reports that Concentric and NEXTLINK have filed with the Securities and Exchange Commission.

      The following table presents on a pro forma basis unaudited data concerning the net income, dividends and book value per share for NEXTLINK after giving effect to the merger and the LHP share exchange, assuming that those transactions occurred as of the beginning of the periods presented:

Pro Forma Basis:

      The following tables present historical per share data for Concentric and NEXTLINK :

Concentric:

NEXTLINK:

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RISK FACTORS

      By voting in favor of the merger, Concentric stockholders will be choosing to invest in the combined company, which involves a high degree of risk. You should consider all of the following risks in deciding whether to vote in favor of the merger. Any of the following risks could materially adversely affect the business, operating results and financial condition of NEXTLINK, Concentric or the combined company. You should consider these factors in conjunction with the information contained elsewhere in this document.

      In light of the following factors, we caution you that you should not consider the past financial performance of NEXTLINK or Concentric to be a reliable indicator of future performance of and or use historical trends to anticipate results or trends in future periods.

RISKS RELATED TO THE MERGER

Difficulties integrating Concentric and NEXTLINK may prevent anticipated benefits of the merger from being realized.

      As a result of the differing nature of Concentric’s and NEXTLINK’s operations, it may be difficult to successfully integrate the products, services, technologies, research and development activities, administration, sales and marketing and other operations of the two companies. Integration difficulties may disrupt the combined company’s business and could prevent the achievement of the potential benefits of the merger. The difficulties, costs and delays involved in integrating the companies, which could be substantial, may include:

	•	distracting management and other key personnel, particularly sales and marketing personnel and senior engineers involved in network deployment, from the business of the combined company;
	•	failure to integrate complex technology, product lines and development plans and the difficulty of maintaining uniform standards, controls, procedures and policies;
	•	potential incompatibility of business cultures;
	•	costs and delays in implementing common systems and procedures, particularly in integrating different information systems;
	•	inability to retain and integrate key management, technical, sales and customer support personnel;
	•	disruptions in the combined sales forces that may result in a loss of current customers or the inability to close sales with potential customers;
	•	additional financial resources that may be needed to fund combined operations;
	•	management’s ability to maximize its financial and strategic position by the incorporation of acquired technology or businesses into its service offerings; and
	•	impairment of relationships with employees and customers as a result of changes in management.

      Any of the above risks could prevent the combined company from realizing significant benefits from the merger.

      If the combined company cannot quickly and efficiently integrate Concentric and NEXTLINK personnel, products and services following the closing of the merger, it will not enjoy the full benefits anticipated from the transaction. Concentric officers and employees have valuable knowledge of the data services and web hosting business that would be difficult to replace if the combined company does not retain the services of a substantial portion of them.

If the average price of NEXTLINK common stock decreases below $69.23 per share prior to the merger, Concentric stockholders will receive less dollar value for their Concentric common stock.

      If the average price per share of NEXTLINK common stock prior to the merger falls below $69.23, the NM Acquisition Corp. common stock received by Concentric stockholders will worth less than $45 per share. Additionally, Concentric does not have “walk-away rights” and consequently cannot terminate the merger

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Some officers and directors of Concentric have conflicts of interest arising out of personal benefits to be received in the merger that could influence their support of the merger.

      Certain of Concentric’s executive officers and directors will receive substantial employment-related benefits in the merger. These benefits constitute a conflict of interest for each of these individuals because these benefits, which Concentric stockholders will not share, give them a personal interest in the merger and could have influenced their support for it. In particular, certain of Concentric’s executive officers and directors will receive stock options at market and nominal exercise prices, shares of restricted stock and cash retention bonuses. The directors and officers of Concentric may therefore have been more likely to vote to approve the merger agreement and the merger than if they did not have these interests. Concentric stockholders should consider whether these interests may have influenced these directors and officers to support or recommend the merger. You should read more about these interests under “The Merger — Interests of Insiders of Concentric in the Merger” on page 49.

Concentric may not be able to enter into a merger or business combination with another party at a favorable price because of restrictions in the merger agreement.

      While the merger agreement is in effect, subject to specified exceptions, Concentric is prohibited from entering into or soliciting, initiating or encouraging any inquiries or proposals that may lead to a proposal or offer for a merger, consolidation, business combination, sale of substantial assets, tender offer, sale of shares of capital stock or other similar transactions with any person other than NEXTLINK. As a result of this prohibition, Concentric may not be able to enter into an alternative transaction at a favorable price.

The combined company’s success in the Internet/data services market depends upon third-party distribution and engineering relationships, some of which could be jeopardized by the merger.

      An important element of Concentric’s strategy has been to develop relationships with leading companies to enhance its distribution and engineering efforts. Concentric also has technology supply arrangements in place for key components of its web hosting and e-commerce platform. We cannot assure you that the merger won’t adversely affect some or all of these important relationships. NEXTLINK competes with Williams, SBC and Teligent, all of which are important Concentric customers and therefore may make these companies reluctant to deal with the combined company following the merger.

      Concentric has also entered into strategic agreements with SBC and Teligent for the delivery of private-labeled services to their customers. Concentric relies on these relationships for the acquisition of small and medium enterprise customers. Termination of any of these agreements or the combined company’s failure to renew any of the agreements upon termination on terms acceptable to it could have a material adverse effect on its business, financial condition and results of operations. For example, Concentric currently is in the process of winding down its relationship with Teligent to deliver private label services to Teligent’s customers. Concentric expects the relationship to be terminated in 2000. If Concentric does not successfully replace the Teligent relationship, then Concentric may have difficulty attracting new small and medium sized enterprise customers which could have a material adverse impact on the results of operations of the combined enterprise. Concentric has an outsourcing agreement with Williams Technology Solutions, a subsidiary of Williams Communications Group, Inc., that enables Concentric to use Williams employees for the operational support of its network. Concentric’s use of Williams employees and Williams engineering expertise was integral to the development of Concentric’s network and continues to be integral to the ongoing operation of Concentric’s

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If the combined company is required to redeem Concentric senior notes and preferred stock, there will be substantial expenses resulting from the merger that will divert resources from other productive uses.

      Under the terms of the indenture governing Concentric’s 12 3/4% senior notes due 2007, and the terms of its 13 1/2% series B senior redeemable exchangeable preferred stock, upon completion of the merger the combined company will be required to offer to repurchase those outstanding senior notes and shares of preferred stock at a purchase price equal to 101% of the principal amount of the senior notes and 101% of the liquidation preference of the shares of preferred stock. As of March 31, 2000, the total principal amount of the senior notes and the liquidation preference of the shares of preferred stock outstanding was approximately $338.7 million. If the combined company is required to utilize available cash to fund repurchase of all or a significant amount of Concentric’s senior notes and preferred stock, it would reduce the amount of funds available to implement the business plan of the combined company.

RISKS RELATED TO THE BUSINESS AND OPERATIONS OF NEXTLINK AND CONCENTRIC

      The risks set forth below are a number of the risks relating to the business and operations of Concentric and NEXTLINK. It is important for stockholders of Concentric and NEXTLINK to understand these risks because, after the merger, they could harm the business of the combined company.

  Risks Related to Liquidity and Capital Resources

NEXTLINK and Concentric have substantial existing debt and the combined company will incur substantial additional debt, in addition to NEXTLINK’s and Concentric’s records of increasing losses and negative cash flow.

      As of March 31, 2000 NEXTLINK had outstanding nine issues of senior notes totaling $3,733.3 million in principal amount, approximately $4.1 million in miscellaneous debt obligations of its subsidiaries, and two series of redeemable preferred stock. These redeemable preferred stock series include 8,324,796 shares of 14% redeemable preferred stock, with a liquidation preference of $50 per share, and 4,000,000 shares of 6 1/2% preferred stock, with a liquidation preference of $50 per share. NEXTLINK has also issued 584,357 shares of Series C cumulative convertible participating preferred stock and 265,625 shares of Series D convertible participating preferred stock, both with a liquidation preference of $1,000 per share. NEXTLINK has also obtained a $1,000.0 million credit facility, of which $375.0 million has been drawn.

      At March 31, 2000 Concentric’s total debt (including the current portion) was $214.8 million, and stockholders’ equity was $62.2 million. Interest on this indebtedness totaled approximately $22.6 million in 1999. Concentric also issued 150,000 shares of preferred stock in June 1998 with dividends which accrue at the rate of 13 1/2 % per year and 50,000 shares of preferred stock in June 1999 with dividends which accrue at the rate of 7% per year.

      The combination of NEXTLINK’s and Concentric’s debt, including preferred stock, will have important consequences for the combined company, including the following:

	•	its ability to obtain additional financing in the future, whether for working capital, capital expenditures, acquisitions or other purposes, may be impaired;
	•	a substantial portion of its cash flow from operations and financing activities will be dedicated to the payment of interest on its debt and dividends on preferred stock, which will reduce the funds available for other purposes;
	•	its flexibility in planning for or reacting to changes in market conditions may be limited; and

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	•	it may be more vulnerable in the event of a downturn in its business.

      For each period since inception, both NEXTLINK and Concentric have incurred substantial and increasing net losses and negative cash flow from operations. Consequently, neither NEXTLINK nor Concentric currently generates, and the combined company may not be able to generate, cash flows from which it can make interest payments on outstanding notes and dividend payments on outstanding preferred stock or fund continuing operations and planned capital expenditures. We cannot know when, if ever, net cash generated by the internal business operations of the combined company will support its growth and continued operations. If the combined company is unable to generate cash flow in the future sufficient to cover its fixed charges and is unable to borrow sufficient funds from other sources, then it may be required to:

	•	refinance all or a portion of its existing debt and redeemable preferred stock; or
	•	sell all or a portion of its assets.

      If the combined company fails to pay principal and interest on its notes when due, the noteholders could declare default and demand that it repay the entire amount of defaulted notes. Unless the combined company is able to find alternate financing to pay the entire amount, the noteholders could seek a judgment and attempt to seize its assets to satisfy the debt to them. Any action of this type would have a material adverse affect on the business of the combined company and on the market price of its common stock.

      The indentures under which NEXTLINK’s and Concentric’s notes have been issued, and NEXTLINK’s credit facility, will permit the combined company to incur substantial additional debt. We fully expect to draw down the remaining $625.0 million available under NEXTLINK’s credit facility and borrow substantial additional funds in the next several years. This additional indebtedness, together with the indebtedness of Concentric expected to be assumed in connection with the merger, will further increase the risk of a default unless the combined company can establish an adequate revenue base and generate sufficient cash flow to repay its indebtedness. We cannot assure you that the combined company will ever establish an adequate revenue base to produce an operating profit or generate adequate positive cash flow to provide future capital expenditures and repayment of debt.

Neither NEXTLINK nor Concentric has sufficient additional financing commitments to meet the long term needs of the combined company and, if the combined company not successful in raising additional capital, it will not be able to build and maintain its business.

      Building the business of the combined company will require substantial additional capital spending. NEXTLINK’s and Concentric’s capital spending plans have increased substantially over time, as their respective strategies have evolved and their planned networks have grown larger and more robust and service offerings have expanded. The combined company will need to raise additional capital because its anticipated future capital requirements exceed NEXTLINK’s and Concentric’s cash and marketable securities on hand as of March 31, 2000, the $850.0 million that NEXTLINK received in January 2000 in connection with its Forstmann Little investment, the $375.0 million that NEXTLINK received in February 2000 in connection with its credit facility, and the $625.0 million currently available under NEXTLINK’s credit facility, the only current commitment for additional financing for the combined company. If the combined company fails to raise sufficient capital, it may be required to delay or abandon some of its planned future expansion or expenditures, which could have a material adverse effect on its growth and its ability to compete in the telecommunications services industry and generate profits for stockholders, and could even result in a payment default on its existing debt.

The covenants in NEXTLINK’s and Concentric’s indentures and NEXTLINK’s credit facility will restrict the combined company’s financial and operational flexibility, which could have an adverse effect on its results of operations.

      The indentures under which NEXTLINK’s and Concentric’s senior notes have been issued and NEXTLINK’s credit facility contain covenants that restrict, among other things, the ability of the combined company to borrow money, make particular types of investments or other restricted payments, sell assets or

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  Risks Related to NEXTLINK’s Technology and Network Development

If the combined company cannot quickly and efficiently install NEXTLINK’s hardware, it will be unable to generate revenue.

      Each of NEXTLINK’s networks consists of many different pieces of hardware, including switches, routers, fiber optic cables, electronics, and combination radio transmitter/receivers, known as transceivers, and associated equipment, which are difficult to install. If the combined company cannot install this hardware quickly, the time in which customers can be connected to its network and it can begin to generate revenue from NEXTLINK’s network will be delayed. The construction of NEXTLINK’s national fiber optic network is not under NEXTLINK’s control, but is under the control of Level 3 Communications. If Level 3 Communications fails to complete its network on time or if it fails to perform as specified, NEXTLINK’s strategy of linking its local networks to one another and creating an end-to-end national network will be delayed.

Internet-protocol technology has not yet been perfected for full service networks like NEXTLINK’s.

      NEXTLINK plans to rely on IP technology as the principal basis for its planned end-to-end network. Although IP technology is used throughout the Internet, its extension to support other telecommunications applications, such as voice and video, has not yet been perfected, and currently has several deficiencies, including poor reliability and quality. Integrating these technologies into NEXTLINK’s network may prove difficult and may be subject to delays. NEXTLINK cannot assure you that these improvements will become available in a timely fashion or at reasonable cost, if at all, or that the technology choices we make will prove to be cost effective and correct.

The combined company may not be able to connect NEXTLINK’s network to the incumbent carrier’s network on favorable terms.

      NEXTLINK currently requires interconnection agreements with the dominant local telephone company to connect calls between its customers and non-customers. Congress and the telecommunications industry refer to this dominant local carrier as the incumbent local exchange carrier, or the incumbent carrier. We cannot assure you that the combined company will be able to negotiate or renegotiate interconnection agreements in all of NEXTLINK’s markets on favorable terms.

Physical space limitations in office buildings and landlord demands for fees or revenue sharing could limit the combined company’s ability to connect customers directly to NEXTLINK’s networks and reduce the combined company’s operating margins.

      Connecting a customer who is a tenant in an office building directly to NEXTLINK’s network requires installation of in-building cabling through the building’s risers from the customer’s office to NEXTLINK’s fiber in the street or its antenna on the roof. In some office buildings, particularly the premier buildings in the largest markets, the risers are already close to their maximum physical capacity due to the entry of other competitive carriers into the market. Moreover, the owners of these buildings are increasingly requiring competitive telecommunications service providers like NEXTLINK to pay fees or otherwise share revenue as a condition of access. NEXTLINK has not been required to pay these fees in smaller markets it has served in

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NEXTLINK’s deployment of wireless first mile connections could be delayed by a lack of acceptable equipment and by installation risks.

      The Federal Communications Commission, or FCC, licensed NEXTLINK’s broadband wireless spectrum in what it calls the Local Multipoint Distribution Service, or LMDS. LMDS is a newly-authorized service, and equipment vendors are only beginning to offer radios, transceivers and related equipment designed to work at its frequencies. Recently completed field testing revealed that improvements in the price, features and functionality of the point-to-multi-point equipment must be made before NEXTLINK undertakes a broader commercial launch of services using this technology. Although NEXTLINK’s vendors have advised NEXTLINK that these improvements will be incorporated in their second generation equipment, this equipment is still in development. NEXTLINK cannot be certain that commercial quantities of equipment meeting its standards will be available in time to meet its development schedule.

      LMDS direct connections require NEXTLINK to obtain access to rooftops from building owners and to satisfy local construction and zoning rules for antennas and transmitters. The need to obtain these authorizations could be an additional source of delay.

NEXTLINK cannot accurately predict the total cost of its fixed wireless deployment.

      Although NEXTLINK has selected one vendor from which we will purchase LMDS equipment, because NEXTLINK’s fixed wireless development strategy contemplates using a number of equipment vendors, we don’t know precisely how much the equipment the combined company will need will cost. Installation costs are expected to vary greatly, depending on the particular characteristics of the locations to be served. After initial installation, we expect to incur additional costs to reconfigure, redeploy and upgrade our fixed wireless direct connections as technologies improve.

NEXTLINK’s competition against the incumbent carrier in local markets and Concentric’s dependence upon incumbent local carriers may make it more difficult for the combined company to connect new customers to its networks.

      It is expensive and difficult for NEXTLINK to switch a new customer to NEXTLINK’s network because:

	•	a potential customer faces switching costs if it decides to become our customer, and
	•	NEXTLINK requires cooperation from the incumbent carrier.

      NEXTLINK’s principal competitors, the incumbent carriers, are already established providers of local telephone services to all or virtually all telephone subscribers within their respective service areas.

      Their physical connections from their premises to those of their customers are expensive and difficult to duplicate. To complete the new customer provisioning process, NEXTLINK relies on the incumbent carrier to process certain information. The incumbent carriers have a financial interest in retaining their customers, which could reduce their willingness to cooperate with our new customer provisioning requests.

      We cannot assure you that the combined company will be able to overcome these advantages and compete successfully with the incumbent carriers.

      Additionally, Concentric is dependent upon incumbent carriers to provide telecommunications services to it and its customers. Concentric experiences delays from time to time in receiving telecommunications services from these suppliers. We cannot assure you that the combined company will be able to obtain such

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If the combined company loses key personnel and qualified technical staff, our ability to manage the day-to-day aspects of our complex network will be weakened.

      We believe that a critical component for the success of the combined company will be the attraction and retention of qualified professional and technical personnel. If the combined company loses key personnel and qualified technical staff, or is unable to recruit qualified personnel, our ability to manage the day-to-day aspects of our complex network will be weakened. NEXTLINK and Concentric face significant competition in the attraction and retention of personnel who possess the skill sets that they seek.

      In addition, the combined company must also develop and retain a large and sophisticated sales force. If the combined company fails to do so, there will be an adverse effect on its ability to generate revenue and, consequently, its operating cash flow.

  Risks Related to Competition and the Telecommunications and Data Services Industries

The combined company will face competition in local markets from other carriers, putting downward pressure on prices.

      NEXTLINK currently faces, and the combined company will face, competition from recent and potential market entrants, including long distance carriers entering, reentering or expanding their entry into the local exchange marketplace such as AT&T, MCI WorldCom and Sprint (which has agreed to merge with MCI WorldCom). This places downward pressure on prices for local telephone service and for data services and makes it more difficult for NEXTLINK and the combined company to achieve positive operating cash flow. In addition, competition from other companies, such as cable television companies, electric utilities, microwave carriers, wireless telephone system operators and private networks built by large end-users is expected. We cannot assure you that the combined company will be able to compete effectively with these industry participants.

The combined company will face competition in long distance markets, putting downward pressure on prices.

      NEXTLINK also currently faces, and the combined company will face, intense competition from long distance carriers in the provision of long distance services, which places downward pressure on prices for long distance service, including both voice and data services, and makes it difficult for us to achieve positive operating cash flow. Although the long distance market is dominated by three major competitors, AT&T, MCI WorldCom and Sprint (which has agreed to merge with MCI WorldCom), hundreds of other companies also compete in the long distance marketplace. We also anticipate that the incumbent carriers will be competing in the long distance market in the near future. We cannot assure you that the combined company will be able to effectively compete with any of these industry participants.

The combined company will face competition in creating a national broadband network.

      Several of NEXTLINK’s competitors, such as Qwest, Level 3, IXC and Williams, have announced an intention to create end-to-end broadband networks that would compete directly with the network NEXTLINK is building. In addition, the major long-distance and incumbent local carriers have the ability and announced intention to do so as well. We cannot assure you that the combined company will be able to successfully compete with these service providers.

The combined company will face competition for data services.

      Competitors for data services consist of online service providers, Internet service providers and Web hosting providers. New competitors continue to enter this market and include large computer hardware, software, media and other technology and telecommunications companies, including the incumbent carriers.

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Many of these competitors have superior resources, which may place the combined company at a cost and price disadvantage.

      Many of our current and potential competitors have market presence, engineering, technical and marketing capabilities and financial, personnel and other resources substantially greater than those of NEXTLINK and Concentric and those of the combined company. As a result, some of these competitors can raise capital at a lower cost than we can, and they may be able to develop and expand their communications and network infrastructures more quickly, adapt more swiftly to new or emerging technologies and changes in customer requirements, take advantage of acquisition and other opportunities more readily, and devote greater resources to the marketing and sale of their products and services than we can. Also, our competitors’ greater brand name recognition may require us to price our services at lower levels in order to win business. Finally, our competitors’ cost advantages give them the ability to reduce their prices for an extended period of time if they so choose.

The technologies used by NEXTLINK and Concentric may become obsolete, which would limit the ability of the combined company to compete effectively.

      The telecommunications industry is subject to rapid and significant changes in technology. If the combined company does not replace or upgrade technology and equipment that becomes obsolete, it will be unable to compete effectively because it will not be able to meet the expectations of its customers.

      The following technologies and equipment that NEXTLINK uses or will use are subject to obsolescence: wireline and wireless transmission technologies, circuit, and packet switching technologies and data transmission technologies, including the digital subscriber line (DSL), asynchronous transfer mode (ATM) and IP technologies. In addition, we cannot assure you that the technologies that the combined company chooses to invest in will lead to successful implementation of its business plan.

      Additionally, the markets for Concentric’s services are characterized by rapidly changing technology, evolving industry standards, changes in customer needs, emerging competition and frequent new product and service introductions. The future success of the combined company’s data services business will depend, in part, on its ability to accomplish the following in a timely and cost-effective manner:

	•	effectively use leading technologies;
	•	continue to develop its technical expertise;
	•	enhance its current networking services;
	•	develop new services that meet changing customer needs;
	•	advertise and market its services; and
	•	influence and respond to emerging industry standards and other technological changes.

      We believe that the combined company’s ability to compete successfully in the data services market will depend upon the continued compatibility and interoperability of Concentric’s services with products and architectures offered by various vendors. We cannot assure you that industry standards will be established, or, if established, that we can conform to those standards in time to maintain a competitive position. In addition, if the combined company fails to develop successive enhancements to DSL technology or other enhanced services, it may not maintain a competitive position. Also, in order to maintain its competitive position, the

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	•	Internet access through cable television, satellite and wireless modems;
	•	Internet access through screen-based telephones, televisions or other consumer electronic devices; or
	•	subscriber requirements that change the way Internet access is provided.

      Any failure to pursue these technological advances, which may require substantial time and expense, may result in the combined company losing its competitive position and causing a material adverse effect on the combined company’s business. We cannot assure you that we will succeed in adapting Concentric’s network service business to alternate access devices and conduits as they emerge.

      We cannot assure you that the combined company will be successful in effectively using new technologies, developing new services or enhancing its existing services on a timely basis or that such new technologies or enhancements will achieve market acceptance. The combined company’s pursuit of necessary technological advances may require substantial time and expense.

The combined company may be required to pay patent licensing fees, which will divert funds which could be used for other purposes.

      From time to time NEXTLINK and Concentric receive requests to consider licensing certain patents held by third parties that may have bearing on its interactive voice response, other enhanced, or data services. Should the combined company be required to pay license fees in the future, such payments, if substantial, could have a material adverse effect on its results of operations.

      Additionally, if someone asserts a claim relating to Concentric’s proprietary technology or information, the combined company may seek licenses to such intellectual property. We cannot assure you, however, that the combined company could obtain licenses on commercially reasonable terms, if at all. The failure to obtain the necessary licenses or other rights could have a material adverse effect on the combined company’s business, financial condition and results of operations.

NEXTLINK and its industry are, and Concentric and its industry may become, highly regulated, imposing substantial compliance costs and restricting the ability of the combined company to compete in its target markets.

      NEXTLINK is subject to varying degrees of federal, state and local regulation. This regulation imposes substantial compliance costs on NEXTLINK. It also restricts its ability to compete. For example, in each state in which NEXTLINK desires to offer its services, it needs to obtain authorization from the appropriate state commission. NEXTLINK cannot assure you that it will receive authorization for markets to be launched in the future.

      As an operator of value-added networks that provide access to regulated transmission facilities only as part of a data services package, Concentric is not currently subject to direct regulation by the Federal Communications Commission (FCC) or any other governmental agency, other than regulations applicable to businesses generally. However, future changes in law or regulation could result in some aspects of its current operations becoming subject to one or more forms of telecommunication regulation by the FCC or other regulatory agencies.

      The prices at which the combined company may sell Concentric’s services could be affected by regulatory changes:

	•	in the Internet connectivity market;
	•	that indirectly or directly affect telecommunications costs; or
	•	that increase the likelihood or scope of competition from the regional bell operating companies, or RBOCs, that are currently restricted from providing certain services.

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      We cannot predict the effect, if any, that future regulation or regulatory changes may have on the combined company’s business, and we cannot assure you that future regulation or regulatory changes will not have a material adverse effect on the combined company’s business, results of operations or financial condition.

The requirement that NEXTLINK obtain permits and rights-of-way increases its cost of doing business.

      In order for NEXTLINK to acquire and develop its fiber networks, it must obtain local franchises and other permits, as well as rights-of-way and fiber capacity from entities such as incumbent carriers and other utilities, railroads, long distance companies, state highway authorities, local governments and transit authorities. The process of obtaining these permits and rights-of-way increases the cost of doing business.

      We cannot assure you that the combined company will be able to maintain the existing franchises, permits and rights-of-way that it will need to implement its business. Nor can we assure you that the combined company will be able to obtain and maintain the other franchises, permits and rights that it will require. A sustained and material failure to obtain or maintain these rights could materially adversely affect the combined company’s business in the affected metropolitan area.

Continued rapid growth of the combined company’s network, services and subscribers could be slowed if we cannot manage the growth of NEXTLINK’s network.

      NEXTLINK has rapidly expanded and developed its network, services and subscribers, and expect to continue to do so. This has placed and will continue to place significant demands on NEXTLINK’s and the combined company’s management, operational and financial systems and procedures and controls. We may not be able to manage the anticipated growth of the combined company effectively, which would harm its business, results of operations and financial condition. Further expansion and development will depend on a number of factors, including:

	•	technological developments;
	•	the combined company’s ability to hire, train and retain qualified personnel in a competitive labor market;
	•	availability of rights-of-way, building access and antenna sites;
	•	development of customer billing, order processing and network management systems that are capable of serving our growing customer base;
	•	cooperation of the existing local telephone companies;
	•	regulatory and governmental developments; and
	•	existence of strategic alliances or relationships.

      The combined company will need to continue to improve its operational and financial systems and its procedures and controls as it grows. It must also develop, train and manage its employees.

The combined company’s ability to succeed in the data services market is uncertain.

      The combined company’s ability to succeed in the data services market depends to a large extent on its ability to build a tailored, value-added network services business. The combined company’s ability to do so is subject to the following risks:

	•	the data services markets are relatively new, and current and future competitors are likely to introduce competing services or products which may result in market saturation;

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	•	certain critical issues concerning commercial use of tailored, value-added services and Internet services, including, among others, security, reliability, ease and cost of access, and quality of service, remain unresolved and may impact the growth of such services;
	•	the market for data services may fail to grow or grow more slowly than anticipated;
	•	reliability, quality or compatibility problems with new enterprise service offerings which we may introduce could significantly delay or hinder market acceptance and could divert technical and other resources;
	•	the combined company’s inability to obtain sufficient quantities of sole- or limited-source components required to provide data services or to develop alternative sources, if required, could result in delays and increased costs in expanding, and overburdening of, our network infrastructure;
	•	suppliers may not provide the combined company with products or components that comply with Internet standards or that inter-operate with other products or components used in its infrastructure;
	•	capacity constraints that adversely affect the system performance if demand for data services were to increase faster than projected or were to exceed current forecasts;
	•	the combined company’s ability to respond to changing customer requirements or evolving industry trends;
	•	the failure of any link in the delivery chain, including the networks with which the combined company establish public or private peering arrangements or private transit;
	•	the market for tailored value-added network services is extremely competitive, and we expect that competition will intensify in the future;
	•	increased price and other competition due to Internet industry consolidation;
	•	interruptions in service due to a natural disaster, such as an earthquake, or other unanticipated problem; and
	•	liability for information disseminated through our network.

The combined company faces risks associated with international expansion.

      NEXTLINK has begun to expand into Canadian markets and the merger will entail the acquisition of Concentric’s UK operations. The combined company may expand into other international markets in the future. The following risks are inherent in doing business on an international level:

	•	unexpected changes in regulatory requirements;
	•	export restrictions and controls relating to encryption technology;
	•	tariffs and other trade barriers;
	•	difficulties in staffing and managing foreign operations;
	•	longer payment cycles and problems in collecting accounts receivable;
	•	political instability;
	•	fluctuations in currency exchange rates;
	•	seasonal reductions in business activity during the summer months in Europe and certain other parts of the world; and
	•	potentially adverse tax consequences that could adversely impact the success of its international operations.

      We cannot assure you that one or more of such factors will not have a material adverse effect on the existing or future international operations of the combined company and, consequently, on its business,

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OTHER RISKS

Craig O. McCaw, who will control approximately   % of the combined company’s voting power after the merger, may have interests which are adverse to your interests.

      Craig O. McCaw, primarily through his majority ownership and control of Eagle River Investments, L.L.C., will control approximately   % of the combined company’s total voting power after the merger. Because Mr. McCaw has the ability to control the direction and future operations of the combined company and has interests in other companies that may compete with the combined company, he may make decisions that are adverse to your interests.

      Mr. McCaw effectively controls a decision whether a change of control of NEXTLINK will occur. Moreover, Delaware corporate law could make it more difficult for a third party to acquire control of us, even if a change of control could be beneficial to you.

We do not plan on the combined company paying dividends on its common stock.

      We do not anticipate the combined company paying any dividends for the foreseeable future. The NEXTLINK credit facility and the indentures governing the combined company’s senior notes will restrict our ability to pay cash dividends.

  Forward-Looking Statements

Our forward-looking statements are subject to a variety of factors that could cause actual results to differ significantly from current beliefs.

      Some statements and information contained or incorporated in this proxy statement/ information statement/ prospectus are not historical facts, but are “forward-looking statements,” as such term is defined in the Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by the use of forward-looking terminology such as “believes,” “expects,” “plans,” “may,” “will,” “would,” “could,” “should,” or “anticipates,” or the negative of these words or other variations of these words or other comparable words, or by discussions of strategy that involve risks and uncertainties. Such forward-looking statements include, but are not limited to, statements regarding:

	•	market development, the number of markets we expect to serve, and the expected number of addressable business lines in such markets;
	•	network development, including those with respect to IP and ATM network and facilities development and deployment, broadband fixed wireless technology, testing and installation, high speed technologies such as DSL, and matters relevant to our national network;
	•	liquidity and financial resources, including anticipated capital expenditures, funding of capital expenditures and anticipated levels of indebtedness; and
	•	statements with respect to when the merger will be completed and the effects of the merger, including the potential benefits of the merger to Concentric, NEXTLINK and their respective stockholders.

      All such forward-looking statements are qualified by the inherent risks and uncertainties surrounding expectations generally, and also may materially differ from our actual experience involving any one or more of these matters and subject areas. The operation and results of our business also may be subject to the effect of other risks and uncertainties in addition to the relevant qualifying factors identified in the above “Risk

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	•	general economic conditions in the geographic areas that we are targeting for communications services;
	•	the ability to achieve and maintain market penetration and revenue levels sufficient to provide financial viability to our business;
	•	access to sufficient debt or equity capital to meet our operating and financing needs;
	•	the quality and price of similar or comparable communications services offered or to be offered by our competitors; and
	•	future telecommunications-related legislation or regulatory actions.

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THE CONCENTRIC SPECIAL MEETING

General

      Concentric is furnishing this document as a proxy statement to holders of Concentric common stock in connection with the solicitation of proxies by the Concentric board of directors for use at the special meeting of stockholders of Concentric to be held on           , 2000, and any adjournment thereof, and as a prospectus for the NM Acquisition Corp. class A common stock to be issued to holders of Concentric common stock as contemplated by the merger agreement. This document is first being furnished to stockholders of Concentric on or about           , 2000 for their special meeting. This document is also being furnished to NEXTLINK stockholders as an information statement in connection with the merger, and as a prospectus for the NM Acquisition Corp. class A common stock to be issued to holders of NEXTLINK class A common stock and for the NM Acquisition Corp. class B common stock to be issued to holders of NEXTLINK class B common stock, as contemplated by the merger agreement.

Date, Time and Place

      The special meeting will be held on        , 2000, starting at           a.m., Pacific Daylight Time, at the principal executive offices of Concentric at 1400 Parkmoor Avenue, San Jose, California 95126-3429.

Purpose of the Special Meeting

      At the special meeting, Concentric stockholders will consider and vote upon a proposal to adopt the merger agreement and to approve the transactions it contemplates.

Board Recommendation

      The Concentric board has determined that the merger is advisable and fair to, and in the best interests of, Concentric and its stockholders. The Concentric board has therefore unanimously approved the merger and the merger agreement and recommends that stockholders vote for approval of the merger and the merger agreement. When considering the recommendation of the Concentric board, you should be aware that the terms of the merger gives a number of Concentric directors, executive officers and key employees substantial interests in the merger that are different from, or in addition to, the interests of Concentric stockholders, including stock option grants at market and nominal exercise prices, shares of restricted stock and cash retention bonuses. The board of directors of Concentric was aware of these interests at the time it adopted the merger agreement and approved the merger. See “The Merger — Interests of Certain Insiders of Concentric in the Merger.”

      The matters to be considered at the special meeting are of great importance to you as a stockholder of Concentric. Accordingly, we urge you to read and carefully consider the information presented in this proxy statement/information statement/prospectus, and to complete, date, sign and promptly return the enclosed proxy in the enclosed postage-paid envelope.

      You should not send any stock certificates with your proxy card. We will mail you a transmittal form with instructions for the surrender of Concentric common stock certificates promptly after completion of the merger.

Record Date; Voting Rights

      Only holders of record of Concentric common stock at the close of business on the record date,        , 2000, are entitled to receive notice of and to vote at the special meeting. At the close of business on the record date, there were           shares of Concentric common stock outstanding, held by approximately           record holders. Each share of Concentric common stock entitles the record holder of the share to one vote.

      On the record date, the directors and executive officers of Concentric and their affiliates beneficially owned and were entitled to vote  shares of Concentric common stock, or approximately           percent of the shares of Concentric common stock outstanding, on the record date.

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Quorum

      To constitute a quorum for the special meeting, stockholders entitled to cast at least a majority of the votes that all stockholders of Concentric are entitled to cast on the merger agreement and the merger must be present in person or by properly executed proxy. Concentric common stock represented by proxies which are marked “ABSTAIN” will be counted as shares present for purposes of determining the presence of a quorum on all matters, as will shares that are represented by proxies that are executed by any broker, fiduciary or other nominee on behalf of the beneficial owner(s) of the shares regardless of whether authority to vote is withheld from the broker, fiduciary of nominee on one or more matters. If a quorum is not present at the special meeting, it is expected that the meeting will be adjourned to solicit additional proxies.

Voting of Proxies

      To assure that your shares are represented at the special meeting, we urge you to complete, date and sign the enclosed proxy and promptly return it in the enclosed envelope or otherwise mail it to Concentric.

      Concentric stockholders may also vote their shares in person at the special meeting. In order to vote in person at the special meeting, Concentric stockholders must attend the special meeting and cast their votes according to the voting procedures announced at the special meeting. If your shares are held in “street name” by your broker, your broker will vote your shares only if you provide instructions on how to vote. Your broker will provide directions on how to instruct the broker to vote your shares.

      Stockholders may revoke their proxies at any time prior to their use. Proxies may be revoked by:

	•	filing, with the Secretary of Concentric, before taking the vote at the special meeting, a written notice of revocation bearing a later date than the date of the proxy or a later-dated proxy relating to the same shares; or
	•	attending the special meeting and voting in person. Attendance at the special meeting will not in and of itself constitute a revocation of a proxy. Any written notice of revocation or subsequent proxy must be sent so as to be delivered at or before the taking of the vote at the special meeting.

      Concentric stockholders who require assistance in changing or revoking a proxy should contact Pete Bergeron at the address or phone number provided in this document under the caption “Where You Can Find More Information.”

      All shares of Concentric common stock represented by proxies properly received prior to or at the special meeting and not revoked will be voted in accordance with their instructions indicated on such proxies. If Concentric stockholders do not indicate any instructions on a proxy properly executed and returned, that proxy will be voted FOR the merger proposal.

      If any other matters are properly presented at the special meeting for consideration, the persons named in the enclosed form of proxy, and acting under that proxy, will have discretion to vote on such matters in accordance with their best judgment, unless authorization to use that discretion is withheld. If a proposal to adjourn the special meeting is properly presented, the persons named in the enclosed form of proxy will not have discretion to vote shares voted against any of the proposals related to the approval of the merger in favor of the adjournment proposal. Concentric’s board does not currently intend to bring any other business before the special meeting, and so far as Concentric’s board knows, no other matters are to be brought before the special meeting.

      Abstentions may be specified on the merger proposal. Since the favorable vote of holders of a majority of the outstanding shares of Concentric common stock on the merger proposal is required to approve the proposal, a proxy marked “ABSTAIN” with respect to any such proposal will have the effect of a vote against that proposal. In addition, the failure of a Concentric stockholder in connection with the merger proposal to return a proxy will have the effect of a vote against the proposal.

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Vote Required to Approve the Merger Agreement and the Merger

      Under Delaware law, the affirmative vote of a majority of the outstanding Concentric common stock entitled to vote is required to approve the merger agreement and the merger. On the record date, there were           shares of Concentric common stock outstanding and entitled to vote and, thus, the affirmative vote of        shares is required for approval.

      Pursuant to voting agreements, directors and executive officers of Concentric beneficially owning an aggregate of 1,925,842 shares of Concentric common stock, including shares issuable upon exercise of options, as of the record date, or   % of the shares of Concentric common stock outstanding on that date, have agreed to vote their shares of Concentric common stock in favor of the merger and the merger agreement.

Abstentions and Broker Non-Votes

      Under the General Corporation Law of the State of Delaware, an abstaining vote and a broker “non-vote” are counted as present and entitled to vote and are, therefore, included for purposes of determining whether a quorum of shares is present at a meeting; however, such votes are not deemed to be “votes cast.” As a result, abstentions and broker “non-votes” are not included in the tabulation of the voting results for approval of the merger and the merger agreement. A broker “non-vote” occurs when a nominee holding shares for a beneficial owner does not vote on a particular proposal because the nominee does not have discretionary voting power with respect to that item and has not received instructions from the beneficial owner. Because the required vote of the Concentric stockholders to adopt the merger agreement and the merger is based upon the number of outstanding shares of Concentric common stock, rather than upon the shares actually voted, the failure by the holder of any shares to submit a proxy or to vote in person at the Concentric meeting (including abstentions and broker non-votes) will have the same effect as a vote against the adoption of the merger agreement and the merger.

Solicitation of Proxies and Expenses

      Concentric has retained the services of ChaseMellon Consulting Services, LLC to assist in the solicitation of proxies from its stockholders. The fees to be paid by Concentric to ChaseMellon Consulting Services, LLC for these services are not expected to exceed $20,000 plus reasonable out-of-pocket expenses. Concentric will bear its own expenses in connection with the solicitation of proxies for the special meeting of stockholders, except that Concentric and NEXTLINK each will pay one-half of all filing and other fees (other than fees to be paid by Eagle River in connection with the LHP share exchange) paid to the SEC in connection with the registration statement and this proxy statement/information statement/prospectus.

      In addition to solicitation by mail, the directors, officers and employees of Concentric may solicit proxies from their stockholders by telephone, facsimile or in person. Brokerage houses, nominees, fiduciaries and other custodians will be requested to forward soliciting materials to beneficial owners and will be reimbursed for their reasonable expenses incurred in sending proxy materials to beneficial owners.

Appraisal Rights

      Under Delaware law, Concentric stockholders are not entitled to appraisal rights in connection with the merger.

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THE MERGER

      This section describes material aspects of the proposed merger and related transactions. While we believe that the description covers the material terms of the merger and the related transactions, this summary may not contain all of the information that is important to you. You should read the entire merger agreement, which is incorporated by reference and attached to this proxy statement/information statement/prospectus as Appendix A, and the other documents we refer to carefully and in their entirety for a more complete understanding of the merger.

Background of the Merger

      In the summer of 1999, NEXTLINK conducted an internal study of the Internet Service Provider (ISP)/data services market. The intent was to evaluate potential strategic partners with positions in ISP, web hosting and e-commerce services that would complement NEXTLINK’s position as a leading competitive local exchange carrier (CLEC)/emerging broadband data company. NEXTLINK narrowed the target list of potential strategic partners and set up several meetings, including with Concentric, to discuss possible business/strategic relationship opportunities.