<PAGE>

         ___________________________________________________________________
         ___________________________________________________________________
                                           
                                           
                                           
                           NEXTLINK COMMUNICATIONS, L.L.C.
                                           
                                         AND 
                                           
                                NEXTLINK CAPITAL, INC.
                                       Issuers
                                           
                         NEXTLINK COMMUNICATIONS MERGER, INC.
                    (Successor to NEXTLINK Communications, L.L.C.
                                         and
                    to be known as NEXTLINK COMMUNICATIONS, INC.)
                                           
                                         and
                                           
                       UNITED STATES TRUST COMPANY OF NEW YORK
                                       Trustee
                                           
                                           
                                           
                       ________________________________________
                                           
                                        FIRST
                                SUPPLEMENTAL INDENTURE
                             Dated as of January 31, 1997
                                           
                                       Amending
                                           
                                      INDENTURE
                              Dated as of April 25, 1996
                                           
                       ________________________________________
                                           
                                           
                                     $350,000,000
                                           
                                  121/2% Senior Notes
                                  Due April 15, 2006
                                           
                                           
         ___________________________________________________________________
         ___________________________________________________________________

<PAGE>

               THIS FIRST SUPPLEMENTAL INDENTURE, dated as of January 31, 1997
(herein called the "Supplement"), is between NEXTLINK COMMUNICATIONS, L.L.C., a
limited liability company formed under the laws of the State of Washington
(herein called the "Company") and NEXTLINK CAPITAL, INC., a corporation
organized and existing under the laws of the State of Washington and a wholly
owned subsidiary of the Company ("Capital"), as joint and several obligors
(collectively, the "Issuers"), each having its principal office at 155 108th
Avenue N.E., 8th Floor, Bellevue, Washington 98004, NEXTLINK COMMUNICATIONS
MERGER, INC., a corporation organized and existing under the laws of the State
of Washington and the successor in interest to the Company ("INC") and UNITED
STATES TRUST COMPANY OF NEW YORK, duly organized and existing under the laws of
the State of New York, as Trustee (herein called the "Trustee").  Upon
consummation of the Merger, INC will change its name to NEXTLINK Communications,
Inc.

                               RECITALS OF THE ISSUERS
                                           
          WHEREAS, pursuant to the terms of the Indenture, dated as of April 25,
1996 (herein called the "Original Indenture"), between the Issuers and the
Trustee, the Issuers have issued $350,000,000 principal amount of 121/2% Senior
Notes due April 15, 2006 (herein called the "Securities"); and

          WHEREAS, pursuant to the terms of that certain Agreement and Plan of
Merger, dated as of January 23, 1997, by and among the Company and INC, the
Company merged with and into INC, with INC as the surviving corporation (the
"Merger"); and

          WHEREAS, the Prospectus dated July 31, 1996 pursuant to which the
Securities were issued states that in a manager managed limited liability
company such as the Company, there is no board of directors, but pursuant to the
terms of the Company's Amended and Restated Limited Liability Company Agreement,
management of the Company is vested in the Managing Members; and

          WHEREAS, as a result of the Merger, INC will change its name to
NEXTLINK Communications, Inc. and as the surviving corporation of the Merger
will be a corporation with a board of directors; and

          WHEREAS, Section 901 of the Original Indenture provides for the
execution and delivery by the Issuers and, subject to the provisions of Section
903 of the Original Indenture, by the Trustee of one or more supplemental
indentures, without the consent of the Holders of the Securities, for the
purposes specified therein; and

          WHEREAS, pursuant to the provisions of Section 801 and assuming the
requirements of such Section are satisfied, the Company is permitted to become a
corporation through a merger transaction in which the Company is not the
surviving corporation, and under the Original Indenture, the Issuers and the
Trustee may enter into a supplemental indenture, "to evidence the succession of
another Person to either of the Issuers and the assumption by such successor of
the covenants of the Issuers contained in the Securities," which supplement,
pursuant to Section 901 of the Original Indenture, does not require the consent
of the Holders of the Securities; and

          WHEREAS, Section 901 of the Original Indenture also allows the
execution and delivery of a Supplemental Indenture "to add to the covenants of
the Issuers for the benefit of the Holders, or to surrender any right or power
herein conferred upon the Issuers," and


<PAGE>

          WHEREAS, Section 901 of the Original Indenture further allows the
execution and delivery of a Supplemental Indenture "to cure any ambiguity, to
correct or supplement any provision herein which may be inconsistent with any
other provision herein, or to make any other provisions with respect to matters
or questions arising under this Indenture which shall not be inconsistent with
the provisions of this Indenture, provided that such action is pursuant to this
Indenture, PROVIDED that such action pursuant to this Clause 5 shall not
adversely affect the legal rights of the Holders," and

          WHEREAS, the definition of "Change of Control" addresses only the
situation where the Company remains a limited liability company and does not
address what would constitute a "Change of Control" should the Company become a
corporation, which was specifically contemplated at the time of the execution of
the Original Indenture as indicated in clause (5) of Section 801(a) of the
Original Indenture; and

          WHEREAS, the Issuers desire to further evidence that a corporation has
succeeded to the Company by modifying certain other provisions of the Original
Indenture, including the definition of "Board of Directors," Board Resolution,"
"Change of Control" and "Managing Member's Certificate;" and

          WHEREAS, pursuant to the provisions of Section 801(b) INC wishes by
this Supplemental Indenture to evidence its succession to the Company and its
assumption of the covenants of the Company contained in the Original Indenture
and the Securities and pursuant to the provisions of Section 802 INC shall
succeed to, and be substituted for, and may exercise every right and power of,
the Company under the Original Indenture; and

          WHEREAS, all things necessary to make this Supplement, when executed
and delivered by the Trustee, the valid agreement of the Issuers and INC in
accordance with its terms have been done.

          NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:
                                           
          SECTION 101.  Definitions.  Except as otherwise expressly provided 
herein, all capitalized words and terms used herein shall have the respective 
meanings ascribed thereto in Article One of the Original Indenture.

          SECTION 102.  Amendment of Original Indenture.

          (a)  The definition of "Board of Directors" contained in Section 
101 of the Original Indenture is hereby amended and restated in its entirety 
to read as follows (new language is indicated in BOLD ITALICS for convenience 
of reference):

               "Board of Directors" means, the Board of Directors of THE COMPANY
          OR Capital, AS THE CASE MAY BE, or any duly authorized committee of
          that board.
          
          (b)  The definition of "Board Resolution " contained in Section 101 
of the Original Indenture is hereby amended and restated in its entirety to 
read as follows (new language is indicated in BOLD ITALICS for convenience of 
reference):

               "Board Resolution " means, in respect of THE COMPANY OR Capital,
          a copy of a resolution certified by the Secretary or any Assistant
          Secretary of THE COMPANY OR Capital, AS THE CASE MAY BE, to have been
          duly adopted by the Board of Directors and 

                                          2
<PAGE>

          to be in full force and effect on the date of such certification, and
          delivered to the Trustee..

          (c)  The definition of "Managing Member's Certificate" contained in 
Section 101 of the Original Indenture is hereby deleted.

          (d)  The definition of "Change of Control" contained in Section 
1016(c) of the Original Indenture is hereby amended and restated in its 
entirety to read as follows (new language is indicated in BOLD ITALICS for 
convenience of reference):

               (c)  A "Change of Control"  will be deemed to have occurred at
          such time as either (a) any Person or any Persons acting together that
          would constitute a "group" (a "Group") for purposes of Section 13D of
          the Exchange Act, or any successor provision thereto (other than Eagle
          River, Mr. Craig O. McCaw and their respective affiliates or an
          underwriter engaged in a firm commitment underwriting on behalf of the
          Company) shall beneficially own (within the meaning of Rule 13d-3
          under the Exchange Act, or any successor provision thereto) more than
          50% of the aggregate voting power of all classes of Voting Stock of
          the Company; or (b) (I) SO LONG AS THE COMPANY REMAINS A LIMITED
          LIABILITY COMPANY, neither Eagle River nor any Affiliate of Mr. Craig
          O. McCaw or Eagle River shall be a Managing Member of the Company OR
          (II) SO LONG AS THE COMPANY IS A CORPORATION, NEITHER MR. CRAIG O.
          MCCAW NOR ANY PERSON DESIGNATED BY HIM TO THE COMPANY AS ACTING ON HIS
          BEHALF SHALL BE A DIRECTOR OF THE COMPANY; OR (C) DURING ANY PERIOD OF
          TWO CONSECUTIVE YEARS, INDIVIDUALS WHO AT THE BEGINNING OF SUCH PERIOD
          CONSTITUTED THE BOARD OF DIRECTORS OF THE COMPANY (TOGETHER WITH ANY
          NEW DIRECTORS WHOSE ELECTION BY THE BOARD OF DIRECTORS OF THE COMPANY
          OR WHOSE NOMINATION FOR ELECTION BY THE SHAREHOLDERS OF THE COMPANY
          WAS PROPOSED BY A VOTE OF A MAJORITY OF THE DIRECTORS OF THE COMPANY
          THEN STILL IN OFFICE WHO WERE EITHER DIRECTORS AT THE BEGINNING OF
          SUCH PERIOD OR WHOSE ELECTION OR NOMINATION FOR ELECTION WAS
          PREVIOUSLY SO APPROVED) CEASE FOR ANY REASON TO CONSTITUTE A MAJORITY
          OF THE BOARD OF DIRECTORS OF THE COMPANY THEN IN OFFICE.
          

          SECTION 103.  SUCCESSOR SUBSTITUTION.  

          (a)  Pursuant to the provisions of Section 801(b) INC hereby 
acknowledges and agrees that it has succeeded the Company as the Company 
under the Indenture and the Securities, and does hereby assume and agree to 
perform all of the obligations of the Company under the Indenture and the 
Securities and does otherwise agree to be bound by and subject to the terms 
and provisions of the Indenture and the Securities in each and every respect 
as if it had been initially named as the Company therein.  Without in any way 
limiting the generality of the foregoing, INC hereby agrees to be liable for 
the due and punctual payment of principal of (and premium, if any) and 
interest on all of the Securities.

          (b)  All references in the Original Indenture to any action to be 
taken by a Managing Member shall be amended and restated to provide that such 
action shall be taken by the Board of Directors of INC, and that all action 
of a Managing Member that is required to be evidenced by an Managing Member's 
Certificate shall be evidenced by an Officers' Certificate.

          (c)  In order to further evidence the succession of INC to the 
Company and INC's assumption of the covenants of the Company under the 
Indenture and the Securities, the form of Securities set forth in 

                                          3
<PAGE>

ARTICLE TWO of the Original Indenture are hereby amended by replacing, in their
entirety, such forms of Securities with the form of Securities set forth in
Exhibit A hereto.  In exchange for any Security outstanding under the Original
Indenture, INC shall issue, and the Trustee shall authenticate, a new Security
in accordance with the provisions of the Indenture.

          SECTION 104.  Representations of INC  INC hereby represents and 
warrants to the Trustee that as of the date hereof:

          (a)  INC is a corporation validly existing and in good standing 
under the laws of the State of Washington; and

          (b)  no Default or Event of Default will result from the Merger or 
the execution and delivery of this Supplemental Indenture.

          SECTION 105.  Construction with Original Indenture.  All of the 
covenants, agreements and provisions of this Supplement shall be deemed to be 
and construed as part of the Original Indenture and VICE VERSA to the same 
extent as if fully set forth verbatim therein and herein and shall be fully 
enforceable in the manner provided in the Original Indenture.  Except as 
provided in this Supplement, the Original Indenture shall remain in full 
force and effect and the terms and conditions thereof are hereby confirmed.

          SECTION 106.  Conflict with Trust Indenture Act.  If any provision 
hereof limits, qualifies or conflicts with a provision of the Trust Indenture 
Act that is required under such Act to be part of and govern the Original 
Indenture or this Supplement, the latter provision shall control.  If any 
provision hereof modifies or excludes any provision of the Trust Indenture 
Act that may be so modified or excluded, the latter provision shall be deemed 
to apply to this Supplement as so modified or to be excluded, as the case may 
be.

          SECTION 107.  Effect of Headings.  The Section headings herein are 
for convenience only and shall not affect the construction hereof.

          SECTION 109.  Separability Clause.  In case any provision in this 
Supplement shall be invalid, illegal or unenforceable, the validity, legality 
and enforceability of the remaining provisions shall not in any way be 
affected or impaired thereby, it being intended that all of the provisions 
hereof shall be enforceable to the full extent permitted by law.

          SECTION 110.  Benefits of Supplement and Original Indenture.  
Nothing in this Supplement or the Original Indenture or in the Securities, 
express or implied, shall give to any Person other than the parties hereto 
and thereto and their successors hereunder and thereunder and the Holders of 
Securities, any benefit or any legal or equitable right, remedy or claim 
under this Supplement or the Original Indenture.  Neither this Supplement nor 
the Original Indenture may be used to interpret another indenture, loan 
agreement or debt agreement of the Issuers, INC or any of their respective 
Subsidiaries.  No such other indenture or loan or debt agreement may be 
utilized to interpret this Supplement or the Original Indenture.

          SECTION 111.  GOVERNING LAW.  THIS SUPPLEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

          SECTION 112.  No Recourse Against Others.  A director, member, 
managing member officer, employee, stockholder or incorporator, as such, of 
the Issuers or INC shall not have any liability for any 

                                          4
<PAGE>

obligations of the Issuers or INC under this Supplement or for any claim based
on, in respect or by reason of such obligations or their creation.

          SECTION 113.  Duplicate Originals.  All parties may sign any number of
copies or counterparts of this Supplement.  Each signed copy or counterpart
shall be an original, but all of them together shall represent the same
agreement.

          SECTION 114.  Effectiveness.  This Supplement shall become 
effective in accordance with the provisions of Article Nine of the Original 
Indenture.

                              [Signature page follows.]

<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Supplement 
to be duly executed, and their respective corporate seals to be hereunto 
affixed and attested, if applicable, all as of the day and year first above 
written.

                                        NEXTLINK COMMUNICATIONS, L.L.C.



                                        By:  /s/ Kathleen H. Iskra
                                             -----------------------------------
Attest:                                 Title:  Vice President

                                              ----------------------------------
      /s/ R. Bruce Easter, Jr.
-----------------------------

                                        NEXTLINK CAPITAL, INC.



                                        By:  /s/ Kathleen H. Iskra
                                             ----------------------------------
Attest:                                 Title:  Vice President
                                              ---------------------------------

     /s/ R. Bruce Easter, Jr.
-----------------------------

                                        NEXTLINK COMMUNICATIONS MERGER, INC.



                                        By:  /s/ Kathleen H. Iskra
                                            ------------------------------------
Attest:                                 Title:  Vice President
                                              ---------------------------------

     /s/ R. Bruce Easter, Jr.
-----------------------------


[SEAL]                                  UNITED STATES TRUST COMPANY OF NEW YORK



                                        By:  /s/ Patricia Stermer
                                             -----------------------------------
Attest:                                 Title:  Assistant Vice President
                                              ---------------------------------

  /s/ Margaret Ciesmelewski    
--------------------------------

                                          6
<PAGE>

STATE OF WASHINGTON        )
                              ss.:
COUNTY OF KING             )


          On the 30th day of January, 1997, before me personally came 
Kathleen H. Iskra, to me known, who, being by me duly sworn, did depose and 
say that she is the Vice President or NEXTLINK, Inc. a Managing Member of 
NEXTLINK COMMUNICATIONS, L.L.C., one of the limited liability companies 
described in and which executed the foregoing instrument, and duly 
acknowledged to me that she executed the same by authority of the Managing 
Members of said limited liability company.

                                             /s/ Nancy L. Stead
                                        ----------------------------------------




STATE OF WASHINGTON        )
                              ss.:
COUNTY OF KING             )


          On the 30th day of January, 1997, before me personally came 
Kathleen H. Iskra, to me known, who, being by me duly sworn, did depose and 
say that she is the Vice President or NEXTLINK CAPITAL, INC., one of the 
corporations described in and which executed the foregoing instrument, and 
duly acknowledged to me that she executed the same by authority of the Board 
of Directors of said corporation.

                                             /s/ Nancy L. Stead
                                        ----------------------------------------





                                          7
<PAGE>

STATE OF WASHINGTON        )
                              ss.:
COUNTY OF KING             )


          On the 30th day of January, 1997, before me personally came 
Kathleen H. Iskra, to me known, who, being by me duly sworn, did depose and 
say that she is the Vice President or NEXTLINK COMMUNICATIONS, INC., one of 
the corporations described in and which executed the foregoing instrument, 
and duly acknowledged to me that she executed the same by authority of the 
Board of Directors of said corporation.

                                             /s/ Nancy L. Stead
                                        ----------------------------------------






STATE OF NEW YORK      )
                            ss.:
COUNTY OF NEW YORK     )


          On the 31st day of January, 1996, before me personally came Patricia
Stermer, to me known, who, being by me duly sworn, did depose and say that she
is Asst. Vice President of UNITED STATES TRUST COMPANY OF NEW YORK, one of the
corporations described in and which executed the foregoing instrument; that
he/she knows the seal of said corporation; that the seal affixed to said
instrument is such corporate seal; that it was so affixed by authority of the
By-Laws of said corporation, and that he/she signed his/her name thereto by like
authority.



                                             /s/ Christopher Grell
                                        ---------------------------------------




                                          8

<PAGE>


 EXHIBIT A

Form of Face of Security 

               [If a Global Security not to be held by The Depository Trust 
Company, then insert -THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING 
OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A 
DEPOSITARY OR A NOMINEE THEREOF.  THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE 
OR IN PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN 
WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH 
DEPOSITARY OR A NOMINEE THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES 
DESCRIBED IN THE INDENTURE.]

               [If a Global Security to be held by The Depository Trust Company,
then insert - UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED 
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION 
("DTC"), TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR 
PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. 
OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC 
(AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS 
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR 
OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL 
INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.]

               [If a Temporary Regulation S Global Security, then insert -THIS
SECURITY IS A TEMPORARY REGULATION S GLOBAL SECURITY WITHIN THE MEANING OF THE
INDENTURE REFERRED TO HEREINAFTER. EXCEPT IN THE CIRCUMSTANCES DESCRIBED IN
SECTION 305(c) OF THE INDENTURE, INTERESTS IN THIS TEMPORARY REGULATION S GLOBAL
SECURITY MAY NOT BE OFFERED OR SOLD TO A U.S. PERSON OR FOR THE ACCOUNT OR
BENEFIT OF A U.S. PERSON PRIOR TO THE EXPIRATION OF THE RESTRICTED PERIOD (AS
DEFINED IN THE INDENTURE), AND NO TRANSFER OR EXCHANGE OF AN INTEREST IN THIS
TEMPORARY REGULATION S GLOBAL SECURITY MAY BE MADE FOR AN INTEREST IN A
RESTRICTED GLOBAL SECURITY OR IN A PERMANENT REGULATION S GLOBAL SECURITY UNTIL
AFTER THE LATER OF THE DATE OF EXPIRATION OF THE RESTRICTED PERIOD AND THE DATE
ON WHICH THE OWNER SECURITIES CERTIFICATION AND THE DEPOSITORY SECURITIES
CERTIFICATION RELATING TO SUCH INTEREST HAVE BEEN PROVIDED IN ACCORDANCE WITH
THE TERMS OF THE INDENTURE, TO THE EFFECT THAT THE BENEFICIAL OWNER OR OWNERS OF
SUCH INTEREST ARE NOT U.S. PERSONS.]

              [If a Permanent Regulation S Security, then insert -THE SECURITIES
EVIDENCED HEREBY HAVE NOT BEEN REGISTERED UNDER THE UNITED STATES SECURITIES ACT
OF 1933 (THE "SECURITIES ACT"), AND MAY NOT BE OFFERED, SOLD, OR DELIVERED IN
THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, ANY U.S. PERSON,
UNLESS THE SECURITIES ARE REGISTERED UNDER THE SECURITIES ACT OR AN EXEMPTION
FROM THE REGISTRATION REQUIREMENTS THEREOF IS AVAILABLE.]


                                         A-1

<PAGE>

              [If a Restricted Security, then insert -THE SECURITIES EVIDENCED
HEREBY HAVE NOT BEEN REGISTERED UNDER THE UNITED STATES SECURITIES ACT OF 1933
(THE "SECURITIES ACT")  AND MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE
TRANSFERRED EXCEPT (A) BY THE INITIAL INVESTOR (1) TO A PERSON WHOM THE SELLER
REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF
RULE 144A UNDER THE SECURITIES ACT PURCHASING FOR ITS OWN ACCOUNT OR FOR THE
ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER IN A TRANSACTION MEETING THE
REQUIREMENTS OF RULE 144A, (2) IN AN OFFSHORE TRANSACTION COMPLYING WITH RULE
903 OR RULE 904 OF REGULATION S UNDER THE SECURITIES ACT, (3) PURSUANT TO AN
EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT PROVIDED BY RULE 144
THEREUNDER (IF AVAILABLE) OR (4) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT
UNDER THE SECURITIES ACT AND (B) BY SUBSEQUENT INVESTORS, AS SET FORTH IN (A)
ABOVE OR TO AN INSTITUTIONAL ACCREDITED INVESTOR IN A TRANSACTION EXEMPT FROM
THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT, IN EACH CASE IN ACCORDANCE
WITH ALL APPLICABLE SECURITIES LAWS OF THE STATES OF THE UNITED STATES AND OTHER
JURISDICTIONS.]

                         121/2% SENIOR NOTES DUE April 15, 2006
                                           
                                                        CUSIP NUMBER: __________

No. __________                                                  $_______________

               NEXTLINK Communications, Inc., a corporation formed under the 
laws of the State of Washington (herein called the "Company", which term 
includes any successor Person under the Indenture hereinafter referred to), 
and NEXTLINK Capital, Inc., a Washington corporation and a wholly-owned 
subsidiary of the Company (herein called "Capital", and together with the 
Company, the "Issuers"), for value received, hereby promises to pay to 
__________, or registered assigns, the principal sum of __________ Dollars on 
April 25, 2006, and to pay interest thereon from April 25, 1996 or from the 
most recent Interest Payment Date to which interest has been paid or duly 
provided for, semi-annually on October 15 and April 15 in each year, 
commencing October 15, 1996 at the rate of 121/2 per annum, until the 
principal hereof is paid or made available for payment 

[If Original Securities, then insert:  provided, however, that if (i)
the Issuers have not filed a registration statement under the Securities 
Act of 1933, as amended (the "Securities Act"), registering a security 
substantially identical to this Security (except that such Security will 
not contain terms with respect to the Special Interest payments described
below or transfer restrictions) pursuant to an exchange offer (the 
"Exchange Offer") (the "Exchange Registration Statement") by May 16, 
1996, or (ii) the Exchange Registration Statement relating to the 
Exchange Offer (or, in lieu thereof, a registration statement registering
this Security for resale (a "Resale Registration Statement")) has not 
become or been declared effective by August 23, 1996, or (iii) the Exchange
Offer has not been completed within 30 business days after the date on which
the Exchange Registration Statement has become or been declared effective 
initially (if the Exchange Offer is then required to be made pursuant to the 
Exchange and Registration Rights Agreement (the "Exchange and Registration 
Rights Agreement"), dated as of April 25, 1996, by and between the Issuers,
the Purchasers (as defined therein) and the Holders from time to time of the 
Securities) or (iv) either the Exchange Registration Statement or, if 
applicable, the Resale Registration Statement is filed and declared 
effective (except as specifically permitted therein) but shall thereafter 
cease to be effective without being succeeded promptly by an additional 
registration statement filed and declared effective, in each case (i) 
through (iv) upon the terms and conditions set forth in the Exchange and 
Registration Rights Agreement (each such event referred to in clauses (i)


                                         A-2
<PAGE>

through (iv), a "Registration Default"), then interest will accrue (in 
addition to the stated interest on the Securities) (the "Step-Up") at a rate 
of 0.25% per annum, determined daily, on the principal amount of the 
Securities, for the period from the occurrence of the Registration Default 
until such time (the "Step-Down Date") as no Registration Default is in 
effect and, provided, further, that for each 90-day period that the 
Registration Default continues, the per annum rate of such Special Interest 
shall increase (each such increase, an "Additional Step-Up") by an additional 
0.25% per annum, provided that such rate shall in no event exceed 1.0% per 
annum in the aggregate until the Step-Down Date (after which the interest 
rate will be restored to its initial rate).  The Issuers shall provide the 
Trustee with written notice of the date of any Registration Default and the 
Step-Down Date.  Interest accruing as a result of the Step-Up or an 
Additional Step-Up is referred to herein as "Special Interest."  Accrued 
Special Interest, if any, shall be paid semi-annually in arrears on October 
15 and April 15 in each year; and the amount of accrued Special Interest 
shall be determined on the basis of a 365 or 366 day year, as the case may 
be, and the number of days actually elapsed.  Any accrued and unpaid interest 
(including Special Interest) on this Security upon the issuance of an 
Exchange Security (as defined in the Indenture) in exchange for this Security 
shall cease to be payable to the Holder hereof but such accrued and unpaid 
interest (including Special Interest) shall be payable on the next Interest 
Payment Date for such Exchange Security to the Holder thereof on the related 
Regular Record Date.]  The interest so payable, and punctually paid or duly 
provided for, on any Interest Payment Date will, as provided in such 
Indenture, be paid to the Person in whose name this Security (or one or more 
Predecessor Securities) is registered at the close of business on the Regular 
Record Date for such interest, which shall be March 15 or September 15 
(whether or not a Business Day), as the case may be, next preceding such 
Interest Payment Date.  Any such interest not so punctually paid or duly 
provided for will forthwith cease to be payable to the Holder on such Regular 
Record Date and may either be paid to the Person in whose name this Security 
(or one or more Predecessor Securities) is registered at the close of 
business on a Special Record Date for the payment of such Defaulted Interest 
to be fixed by the Trustee, notice whereof shall be given to Holders of 
Securities not less than 10 days prior to such Special Record Date, or be 
paid at any time in any other lawful manner not inconsistent with the 
requirements of any securities exchange on which the Securities may be 
listed, and upon such notice as may be required by such exchange, all as more 
fully provided in said Indenture.

               In the case of a default in payment of principal and premium, 
if any, upon acceleration or redemption, interest shall be payable pursuant 
to the preceding paragraph on such overdue principal (and premium, if any), 
such interest shall be payable on demand and, if not so paid on demand, such 
interest shall itself bear interest at the rate of 1% per annum (to the 
extent that the payment of such interest shall be legally enforceable), and 
shall accrue from the date of such demand for payment to the date payment of 
such interest has been made or duly provided for, and such interest on unpaid 
interest shall also be payable on demand.

               Payment of the principal of (and premium, if any) and interest 
on this Security will be made at the corporate trust office of the Trustee 
and at the office or agency of the Issuers maintained for that purpose in the 
Borough of Manhattan, The City of New York, New York, and at any other office 
or agency maintained by the Issuers for such purpose, in such coin or 
currency of the United States of America as at the time of payment is legal 
tender for payment of public and private debts; provided, however, that at 
the option of the Issuers payment of interest may be made by check mailed to 
the address of the Person entitled thereto as such address shall appear in 
the Security Register.

               The Company shall enter into the Pledge Agreement (as defined 
in the Indenture) and use a portion of the net proceeds of the sale of the 
Securities to the Initial Purchasers (as defined in the Indenture) to 
purchase the securities, which shall initially consist of Government 
Securities (as defined in the Indenture), to be pledged to the Trustee (the 
"Pledged Securities") for the benefit of the Holders 

                                         A-3

<PAGE>

of the Securities in such amount as will be sufficient upon receipt of scheduled
interest and principal payments of such securities, in the opinion of a
nationally recognized firm of independent public accountants selected by the
Company, to provide for payment in full of the first six scheduled interest
payments due on the Securities.  The Pledged Securities will be pledged by the
Company to the Trustee for the benefit of the Holders of the Securities and will
be held by the Trustee in the Pledge Account (as defined in the Indenture)
pending disbursement pursuant to the Pledge Agreement.

           Reference is hereby made to the further provisions of this Security
set forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

           Unless the certificate of authentication hereon has been executed by
the Trustee referred to on the reverse hereof by manual signature, this Security
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

          IN WITNESS WHEREOF, the Issuers have caused this instrument to be duly
executed.

Dated:

                                             NEXTLINK COMMUNICATIONS, INC.


                                                By____________________________
                                                       Title:
Attest:


______________________________
Title:

                                             NEXTLINK CAPITAL, INC. 


                                                By______________________________
                                                       Title:

Attest:


______________________________ Title:

Form of Reverse of Security

               (a)   Temporary Regulation S Global Security.  The form of 
reverse of a Temporary Regulation S Global Security shall be as set forth 
below:

               This Temporary Regulation S Global Security is one of a duly 
authorized issue of Securities of the Issuers designated as its Senior Notes 
due April 15, 2006 (the "Securities") issued under an Indenture, dated as of 
April 25, 1996 (herein called the "Indenture"), between the Issuers and 
United States Trust Company of New York, as trustee (herein called the 
"Trustee", which term includes any successor trustee under the Indenture).  
The Securities are limited in aggregate principal

                                         A-4
<PAGE>

amount to $350,000,000.  Reference is hereby made to the Indenture and all
indentures supplemental thereto for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Issuers, the
Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered.

               Until this Temporary Regulation S Global Security is exchanged 
for a Permanent Regulation S Global Security, the Holder hereof shall not be 
entitled to receive payments of interest hereon; until so exchanged in full, 
this Temporary Regulation S Global Security shall in all other respects be 
entitled to the same benefits as other Securities under the Indenture.

               This Temporary Regulation S Global Security is exchangeable in 
whole or in part for one or more Permanent Regulation S Global Securities or 
Restricted Global Securities only (i) on or after the expiration of the 
Restricted Period and (ii) upon presentation of certificates (accompanied by 
an Opinion of Counsel, if applicable) required by Article 3 of the Indenture. 
 Upon exchange of this Temporary Regulation S Global Security for one or more 
Permanent Regulation S Global Securities or Restricted Global Securities, the 
Trustee shall cancel this Temporary Regulation S Global Security.

               This Temporary Regulation S Global Security shall not become 
valid or obligatory until the certificate of authentication hereon shall have 
been duly manually signed by the Trustee in accordance with the Indenture.  
This Temporary Regulation S Global Security shall be governed by and 
construed in accordance with the laws of the State of New York.

                     SCHEDULE OF EXCHANGES FOR GLOBAL SECURITIES
                                           
               The following exchanges of a part of this Temporary Regulation 
S Global Security for other Global Securities have been made:



<TABLE>
<S>                 <C>                 <C>               <C>                   <C>
                       Amount of           Amount of      Principal Amount
                      decrease in          increase in     of this Global
                    Principal Amount    Principal Amount  Security following       Signature of 
                     of this Global      of this Global   such decrease (or     authorized officer
Date of Exchange       Security             Security          increase)             of Trustee
----------------    -----------------   ----------------  -------------------   ------------------

</TABLE>


                                         A-5
<PAGE>

                (b)  Securities other than a Temporary Regulation S Global 
Security. The form of reverse of all Securities other than a Temporary 
Regulation S Global Security shall be as set forth below:

               This Security is one of a duly authorized issue of Securities 
of the Issuers designated as its Senior Notes due April 15, 2006 (the 
"Securities") issued under an Indenture, dated as of April 25, 1996 (herein 
called the "Indenture"), between the Issuers and United States Trust Company 
of New York, as trustee (herein called the "Trustee", which term includes any 
successor trustee under the Indenture).  The Securities are limited in 
aggregate principal amount to $350,000,000.  Reference is hereby made to the 
Indenture and all indentures supplemental thereto for a statement of the 
respective rights, limitations of rights, duties and immunities thereunder of 
the Issuers, the Trustee and the Holders of the Securities and of the terms 
upon which the Securities are, and are to be, authenticated and delivered.

               The Securities are subject to redemption upon not less than 30 
nor more than 60 days' notice by mail to each Holder of Securities to be 
redeemed at such Holder's address appearing in the Security Register, in 
amounts of $1,000 or an integral multiple of $1,000, at any time on or after 
April 15, 2001 and prior to maturity, as a whole or in part, at the election 
of the Issuers, at the following Redemption Prices (expressed as percentages 
of the principal amount) plus accrued and unpaid interest (including Special 
Interest) to but excluding the Redemption Date (subject to the right of 
Holders of record on the relevant Regular Record Date to receive interest due 
on an Interest Payment that is on or prior to the Redemption Date), if 
redeemed during the 12-month period beginning April 15, of each of the years 
indicated below:

                         Year                Redemption Price
                    ----------------    -----------------------
                         2001                   106.250%
                         2002                   104.167%
                         2003                   102.083%

and thereafter at a Redemption Price equal to 100% of the principal amount,
together in the case of any such redemption with accrued interest to the
Redemption Date, but interest installments whose Stated Maturity is on or prior
to such Redemption Date will be payable to the Holders of such Securities, or
one or more Predecessor Securities, of record at the close of business on the
relevant Record Dates referred to on the face hereof, all as provided in the
Indenture.

               The Securities are further subject to redemption prior to 
April 15, 2001 only in the event that on or before April 15, 1999 the Company 
receives net proceeds from any sale of its Common Equity, in which case the 
Company may, at its option, use all or a portion of any such net proceeds to 
redeem Securities in a principal amount of up to an aggregate amount equal to 
33 1/3% of the original principal amount of the Securities, provided, 
however, that Securities in an amount equal to at least $175 million remain 
Outstanding after such redemption.  Such redemption must occur on a 
Redemption Date within 90 days of any such sale and upon not less than 30 nor 
more than 60 days' notice by mail to each Holder of Securities to be redeemed 
at such Holder's address appearing in the Security Register, in amounts of 
$1,000 or an integral multiple of $1,000 at a Redemption Price of 112.50% of 
their principal amount plus accrued and unpaid interest (including Special 
Interest), if any to but excluding the Redemption Date (subject to the right 
of Holders of record on the relevant Regular Record Date to receive interest 
due on an Interest Payment Date that is on or prior to the Redemption Date).  

                                         A-6

<PAGE>


               The Securities do not have the benefit of any sinking fund
obligations.

               The Indenture provides that, subject to certain conditions, if 
(i) a Change of Control occurs or (ii) certain Net Available Proceeds are 
available to the Issuers as a result of any Asset Disposition, the Issuers 
shall be required to make an Offer to Purchase for all or a specified portion 
of the Securities.

               In the event of redemption or purchase pursuant to an Offer to 
Purchase of this Security in part only, a new Security or Securities of like 
tenor for the unredeemed or unpurchased portion hereof will be issued in the 
name of the Holder hereof upon the cancellation hereof.

               If an Event of Default shall occur and be continuing, the 
principal of all the Securities may be declared due and payable in the manner 
and with the effect provided in the Indenture.

               The Indenture contains provisions for defeasance at any time 
of (i) the entire indebtedness of this Security, or (ii) certain restrictive 
covenants and Events of Default with respect to this Security, in each case 
upon compliance with certain conditions set forth therein.

               Unless the context otherwise requires, the Original Securities 
(as defined in the Indenture) and the Exchange Securities (as defined in the 
Indenture) shall constitute one series for all purposes under the Indenture, 
including without limitation, amendments, waivers, redemptions and Offers to 
Purchase.

               The Indenture permits, with certain exceptions as therein 
provided, the amendment thereof and the modification of the rights and 
obligations of the Issuers and the rights of the Holders of the Securities 
under the Indenture at any time by the Issuers and the Trustee with the 
consent of the Holders of a majority in aggregate principal amount of the 
Securities at the time Outstanding.  The Indenture also contains provisions 
permitting the Holders of specified percentages in aggregate principal amount 
of the Securities at the time Outstanding, on behalf of the Holders of all 
the Securities, to waive compliance by the Issuers with certain provisions of 
the Indenture and certain past defaults under the Indenture and their 
consequences.  Any such consent or waiver by the Holder of this Security 
shall be conclusive and binding upon such Holder and upon all future Holders 
of this Security and of any Security issued upon the registration of transfer 
hereof or in exchange herefor or in lieu hereof, whether or not notation of 
such consent or waiver is made upon this Security.

               No reference herein to the Indenture and no provision of this 
Security or of the Indenture shall alter or impair the obligation of the 
Issuers, which is absolute and unconditional, to pay the principal of (and 
premium, if any) and interest on this Security at the times, place and rate, 
and in the coin or currency, herein prescribed.

               As provided in the Indenture and subject to certain limitations
therein set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Issuers in the Borough of Manhattan, The City of New
York, New York, duly endorsed by, or accompanied by a written instrument of
transfer in form satisfactory to the Issuers and the Security Registrar duly
executed by, the Holder hereof or his attorney duly authorized in writing, and
thereupon one or more new Securities, of authorized denominations and like tenor
and for the same aggregate principal amount, will be issued to the designated
transferee or transferees.

                                         A-7
<PAGE>

               The Securities are issuable only in registered form without 
coupons in denominations of $1,000 and any integral multiple thereof, subject 
to a minimum initial purchase amount of $100,000 for Other Securities.  As 
provided in the Indenture and subject to certain limitations therein set 
forth, Securities are exchangeable for a like tenor and aggregate principal 
amount of Securities of a different authorized denomination, as requested by 
the Holder surrendering the same.

               No service charge shall be made for any such registration of 
transfer or exchange, but the Issuers may require payment of a sum sufficient 
to cover any tax or other governmental charge payable in connection therewith.

               Prior to due presentment of this Security for registration of
transfer, the Issuers, the Trustee and any agent of the Issuers or the Trustee
may treat the Person in whose name this Security is registered as the owner
hereof for all purposes, whether or not this Security be overdue, and none of
the Issuers, the Trustee or any such agent shall be affected by notice to the
contrary.

               Interest on this Security shall be computed on the basis of a 
360-day year of twelve 30-day months; provided, however, that Special 
Interest shall be computed on the basis of a 365 or 366 day year, as the case 
may be, and the number of days actually elapsed.

               All terms used in this Security which are defined in the 
Indenture shall have the meanings assigned to them in the Indenture.

                                         A-8
<PAGE>

                          OPTION OF HOLDER TO ELECT PURCHASE
                                           
               If you want to elect to have this Security purchased in its 
entirety by the Issuers pursuant to Section 1013 or 1016 of the Indenture, 
check the box:

                                         [ ]
                                           
               If you want to elect to have only a part of this Security 
purchased by the Issuers pursuant to Section 1013 or 1016 of the Indenture, 
state the amount: $___________

Dated:________________             Your Signature:____________________
                                  (Sign exactly as name appears on the
                                   other side of this Security)

Signature Guarantee:          ________________________________________
                              Notice:  Signature(s) must be guaranteed
                              by an "eligible guarantor institution"
                              meeting the requirements of the Trustee,
                              which requirements will include
                              membership or participation in STAMP or
                              such other "signature guarantee program"
                              as may be determined by the Trustee in
                              addition to, or in substitution for
                              STAMP, all in accordance with the
                              Securities Exchange Act of 1934, as
                              amended.


                                         A-9
<PAGE>

EXHIBIT B
                                   ANNEX A
                                           
    [FORM OF CERTIFICATION TO BE GIVEN BY HOLDERS OF BENEFICIAL INTEREST
     IN A TEMPORARY REGULATION S GLOBAL SECURITY TO EUROCLEAR OR CEDEL]
                                           
                       OWNER SECURITIES CERTIFICATION
                                           
                        NEXTLINK COMMUNICATIONS, INC.
                           NEXTLINK CAPITAL, INC.
                                           
                   12 1/2% Senior Notes due April 15, 2006
                                   CUSIP No. _____
                                           
               Reference is hereby made to the Indenture, dated as of April 
25, 1996 (the "Indenture"), between NEXTLINK Communications, Inc. and 
NEXTLINK Capital, Inc., as Issuers, and United States Trust Company of New 
York, as Trustee. Capitalized terms used but not defined herein shall have 
the meanings given to them in the Indenture.

               This is to certify that, as of the date hereof, $________ of the
above-captioned Securities (the "Securities") are beneficially owned by non-U.S.
person(s). As used in this paragraph, the term "U.S. person" has the meaning
given to it by Regulation S under the Securities Act of 1933, as amended.

               We undertake to advise you promptly by tested telex on or 
prior to the date on which you intend to submit your certification relating 
to the Securities held by you for our account in accordance with your 
operating procedures if any applicable statement herein is not correct on 
such date, and in the absence of any such notification it may be assumed that 
this certification applies as of such date.

               We understand that this certificate is required in connection 
with certain securities laws of the United States. In connection therewith, 
if administrative or legal proceedings are commenced or threatened in 
connection with which this certificate is or would be relevant, we 
irrevocably authorize you to produce this certificate to any interested party 
in such proceedings. This certificate and the statements contained herein are 
made for your benefit and the benefit of the Issuers and the Initial 
Purchasers.

Dated:______________, ____



By:____________________________________________
   As, or as agent for, the beneficial owner(s) 
   of the Securities to which this certificate 
   relates.

                                         A-1
<PAGE>

                                   ANNEX B
                                           
             [FORM OF CERTIFICATION TO BE GIVEN BY THE EUROCLEAR
                  OPERATOR OR CEDEL BANK, SOCIETE ANONYME]
                                           
                     DEPOSITORY SECURITIES CERTIFICATION
                                           
                        NEXTLINK COMMUNICATIONS, INC.
                           NEXTLINK CAPITAL, INC.
                                           
                   12 1/2% Senior Notes due April 15, 2006
                                   CUSIP No. _____
                                           
               Reference is hereby made to the Indenture, dated as of April 
25, 1996 (the "Indenture"), between NEXTLINK Communications, Inc. and 
NEXTLINK Capital, Inc., as Issuers, and United States Trust Company of New 
York, as Trustee. Capitalized terms used but not defined herein shall have 
the meanings given to them in the Indenture.

               This is to certify that, with respect to U.S.$___________ 
principal amount of the above-captioned Securities (the "Securities"), except 
as set forth below, we have received in writing, by tested telex or by 
electronic transmission, from member organizations appearing in our records 
as persons being entitled to a portion of the principal amount of the 
Securities (our "Member Organizations"), certifications with respect to such 
portion, substantially to the effect set forth in the Indenture.1

               We further certify (i) that we are not making available 
herewith for exchange (or, if relevant, exercise of any rights or collection 
of any interest) any portion of the Temporary Regulation S Global Security 
(as defined in the Indenture) excepted in such certifications and (ii) that 
as of the date hereof we have not received any notification from any of our 
Member Organizations to the effect that the statements made by such Member 
Organizations with respect to any portion of the part submitted herewith for 
exchange (or, if relevant, exercise of any rights or collection of any 
interest) are no longer true and cannot be relied upon as of the date hereof.

               We understand that this certification is required in 
connection with certain securities laws of the United States. In connection 
therewith, if administrative or legal proceedings are commenced or threatened 
in connection with which this certification is or would be relevant, we 

______________
1         Unless Morgan Guaranty Trust Company of New York, London Branch is
otherwise informed by the Agent, the long form certificate set out in the
Operating Procedures will be deemed to meet the requirements of this sentence.

                                         B-1
<PAGE>

irrevocably authorize you to produce this certification to any interested party
in such proceedings. This certificate and the statements contained herein are
made for your benefit and the benefit of the Issuers and the Initial Purchasers.

Dated:  _____________, _______

                Yours faithfully,

[CHEMICAL BANK, as operator of the Euroclear System]
or
[CEDEL BANK, SOCIETE ANONYME]

By______________________________ 



                                         B-2
<PAGE>

                                   ANNEX C
                                           
       [FORM OF CERTIFICATION TO BE GIVEN BY  TRANSFEREE OF BENEFICIAL
           INTEREST IN A  TEMPORARY REGULATION S GLOBAL SECURITY]
                                           
                     TRANSFEREE SECURITIES CERTIFICATION
                                           
                        NEXTLINK COMMUNICATIONS, INC.
                           NEXTLINK CAPITAL, INC.
                                           
                   12 1/2% Senior Notes due April 15, 2006
                                   CUSIP No. _____
                                           
          Reference is hereby made to the Indenture, dated as of April 25, 
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK 
Capital, Inc., as Issuers, and United States Trust Company of New York, as 
Trustee. Capitalized terms used but not defined herein shall have the 
meanings given to them in the Indenture.
          
          For purposes of acquiring a beneficial interest in the Temporary 
Regulation S Global Security, the undersigned certifies that it is not a U.S. 
Person as defined by Regulation S under the Securities Act of 1933, as 
amended.
          
          We undertake to advise you promptly by tested telex on or prior to 
the date on which you intend to submit your certification relating to the 
Securities held by you in which we intend to acquire a beneficial interest in 
accordance with your operating procedures if any applicable statement herein 
is not correct on such date, and in the absence of any such notification it 
may be assumed that this certification applies as of such date.
          
          We understand that this certificate is required in connection with 
certain securities laws of the United States. In connection therewith, if 
administrative or legal proceedings are commenced or threatened in connection 
with which this certificate is or would be relevant, we irrevocably authorize 
you to produce this certificate to any interested party in such proceeding. 
This certificate and the statements contained herein are made for your 
benefit and the benefit of the Issuers and the Initial Purchasers.

Dated:______________, ____

By:_____________________________
    As, or as agent for, the
    beneficial acquiror of the
    Securities to which this
    certificate relates.

                                      C-1

<PAGE>

                                   ANNEX D

     FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF RESTRICTED GLOBAL
             SECURITY TO TEMPORARY REGULATION S GLOBAL SECURITY

   (Exchanges or transfers pursuant to Section 305(c)(3) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

          Reference is hereby made to the Indenture, dated as of April 25, 
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK 
Capital, Inc., as Issuers, and United States Trust Company of New York, as 
Trustee. Capitalized terms used but not defined herein shall have the 
meanings given to them in the Indenture.

          This letter relates to U.S.$___________ aggregate principal amount 
of Securities which are held in the form of the Restricted Global Security 
(CUSIP No. _________) with the Depository in the name of 
[insert name of transferor](the "Transferor"). The Transferor has requested a 
transfer of such beneficial interest in the Securities to a Person who will 
take delivery thereof in the form of an equal aggregate principal amount of 
Securities evidenced by the Temporary Regulation S Global Security (CUSIP No. 
_________) to be held with the Depository in the name of [Euroclear] 
[Cedel Bank, societe  anonyme].

          In connection with such request and in respect of such Securities, 
the Transferor does hereby certify that such transfer has been effected in 
accordance with the transfer restrictions set forth in the Securities and 
pursuant to and in accordance with Regulation S under the Securities Act of 
1933, as amended (the "Securities Act"), and accordingly the Transferor does 
hereby certify that:

          (1)  the offer of the Securities was not made to a person in the 
United States;

          
          
          [(2)  at the time the buy order was originated, the transferee was
outside the United States or the Transferor and any person acting on its 
behalf reasonably believed that the transferee was outside the United States;]1

          
          [(2)  the transaction was executed in, on or through the 
facilities of a designated offshore securities market and neither the 
Transferor nor any person acting on our behalf knows that the transaction was 
pre-arranged with a buyer in the United States;]1

          (3)  no directed selling efforts have been made in contravention 
of the requirements of Rule 903(b) or 904(b) of Regulation S, as applicable; 

___________________
1         Insert one of these two provisions, which come from the definition of
"offshore transaction" in Regulation S.


                                     D-1

<PAGE>


               (4)  the transaction is not part of a plan or scheme to evade the
registration requirements of the Securities Act; and

               (5)  upon completion of the transaction, the beneficial 
interest being transferred as described above is to be held with the 
Depository in the name of [Euroclear] [Cedel Bank, societe anonyme].

               We understand that this certificate is required in connection 
with certain securities laws of the United States. In connection therewith, 
if administrative or legal proceedings are commenced or threatened in 
connection with which this certificate is or would be relevant, we 
irrevocably authorize you to produce this certificate to any interested party 
in such proceeding. This certificate and the statements contained herein are 
made for your benefit and the benefit of the Issuers and the Initial 
Purchasers.

[Insert Name of Transferor]

By:_____________________________
          Name:
          Title:

Dated:  ______________

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.



                                    D-2
<PAGE>


                                 ANNEX E

    FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF  RESTRICTED GLOBAL
             SECURITY TO PERMANENT REGULATION S GLOBAL SECURITY
   (Exchanges or transfers pursuant to Section 305(c)(4) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer


               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

          Reference is hereby made to the Indenture, dated as of April 25, 
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK 
Capital, Inc., as Issuers, and United States Trust Company of New York, as 
Trustee. Capitalized terms used but not defined herein shall have the 
meanings given to them in the Indenture.

          This letter relates to U.S.$___________ aggregate principal amount 
of Securities which are held in the form of the Restricted Global Securities 
(CUSIP No. _________) with the Depository in the name of 
[insert name of transferor](the "Transferor"). The Transferor has requested a 
transfer of such beneficial interest in the Securities to a Person who will 
take delivery thereof in the form of an equal aggregate principal amount of 
Securities evidenced by the Permanent Regulation S Global Security (CUSIP No. 
_________).

          In connection with such request, and in respect of such Securities, 
the Transferor does hereby certify that such transfer has been effected in 
accordance with the transfer restrictions set forth in the Securities and,

(1) with respect to transfers made in reliance on Regulation S under the 
Securities Act of 1933, as amended (the "Securities Act"), the Transferor 
does hereby certify that:

          (A)  the offer of the Securities was not made to a person in the 
United States;

          [(B) at the time the buy order was originated, the transferee was 
outside the United States or the Transferor and any person acting on its 
behalf reasonably believed that the transferee was outside the United 
States;]1

          [(B) the transaction was executed in, on or through the facilities of 
a designated offshore securities market and neither the Transferor nor any 
person acting on our behalf knows that the transaction was pre-arranged with 
a buyer in the United States;]1

          (C)  no directed selling efforts have been made in contravention of 
the requirements of Rule 903(b) or 904(b) of Regulation S, as applicable; and

_________________________
1         Insert one of these two provisions, which come from the definition of
"ofshore transaction" in Regulation S.

                                        E-1
<PAGE>


          (D)  the transaction is not part of a plan or scheme to evade the
registration requirements of the Securities Act; or

(2) with respect to transfers made in reliance on Rule 144 under the Securities
Act, the Transferor does hereby certify that the Securities are being
transferred in a transaction permitted by Rule 144 under the Securities Act.

          We understand that this certificate is required in connection with 
certain securities laws of the United States. In connection therewith, if 
administrative or legal proceedings are commenced or threatened in connection 
with which this certificate is or would be relevant, we irrevocably authorize 
you to produce this certificate to any interested party in such proceeding. 
This certificate and the statements contained herein are made for your 
benefit and the benefit of the Issuers and the Initial Purchasers.

[Insert Name of Transferor]

By:_____________________________
          Name:
          Title:

Dated:  ______________

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.


                                    E-2 

<PAGE>


                                 ANNEX F

         FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF TEMPORARY
        REGULATION S GLOBAL SECURITY OR PERMANENT REGULATION S GLOBAL
                   SECURITY TO  RESTRICTED GLOBAL SECURITY
   (Exchanges or transfers pursuant to Section 305(c)(5) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

           Reference is hereby made to the Indenture, dated as of April 25, 
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK 
Capital, Inc., as Issuers, and United States Trust Company of New York, as 
Trustee. Capitalized terms used but not defined herein shall have the 
meanings given to them in the Indenture.  This letter relates to U.S. 
$___________ principal amount of Securities which are evidenced by an 
aggregate [Temporary Regulation S Global Security (CUSIP No. _________)] 
[Permanent Regulation S Global Security (CUSIP No. _________)] and held with 
the Depository through [Euroclear] [Cedel] (Common Code _______) in the name 
of [insert name of transferor] (the "Transferor"). The Transferor has 
requested a transfer of such beneficial interest in Securities to a person 
that will take delivery thereof in the form of an equal principal amount of 
Securities evidenced by a Restricted Global Security of the same series and 
of like tenor as the Securities (CUSIP No. _________).

          In connection with such request, and in respect of such Securities, 
the Transferor does hereby certify that such transfer is being effected 
pursuant to and in accordance with Rule 144A under the Securities Act and, 
accordingly, the Transferor does hereby further certify that the Securities 
are being transferred to a person that the Transferor reasonably believes is 
purchasing the Securities for its own account, or for one or more accounts 
with respect to which such person exercises sole investment discretion, and 
such person and each such account is a "qualified institutional buyer" within 
the meaning of Rule 144A, in each case in a transaction meeting the 
requirements of Rule 144A and in accordance with any applicable securities 
laws of any state of the United States.

          This certificate and the statements contained herein are made for 
your benefit and the benefit of the Issuers and the Initial Purchasers.

[Insert Name of Transferor]

By:_____________________________
          Name:
          Title:

Dated:  ______________

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.



                                      F-1

<PAGE>

                                   ANNEX G-1

        FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF NON-GLOBAL
              RESTRICTED SECURITY TO RESTRICTED GLOBAL SECURITY
  (Transfers and exchanges pursuant to Section 305(c)(6) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

            Reference is hereby made to the Indenture, dated as of April 25,
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK
Capital, Inc., as Issuers, and United States Trust Company of New York, as
Trustee. Capitalized terms used but not defined herein shall have the meanings
given to them in the Indenture.

            This letter relates to $___________ principal amount of Restricted
Securities held in definitive form (CUSIP No. _____) by [insert name of
transferor] (the "Transferor"). The Transferor has requested an exchange or
transfer of such Securities.

            In connection with such request and in respect of such Securities,
the Transferor does hereby certify that (i) such Securities are owned by the
Transferor and are being exchanged without transfer or (ii) such transfer has
been effected pursuant to and in accordance with Rule 144A or Rule 144 under
the United States Securities Act of 1933, as amended (the "Securities Act") and
accordingly the Transferor does hereby further certify that:

          (1)  if the transfer has been effected pursuant to Rule 144A:

               (A)  the Securities are being transferred to a person that the
           Transferor reasonably believes is  purchasing the Securities for its
           own account, or for one or more accounts with respect to which such
           Person exercises sole investment discretion;

               (B)  such Person and each such account is a "qualified 
           institutional buyer" within the meaning of Rule 144A; and

               (C)  the Securities have been transferred in a transaction 
           meeting the requirements of Rule 144A and in accordance with any
           applicable securities laws of any state of the United States; or

          (2)  if the transfer has been effected pursuant to Rule 144:

               (A)  more than two years has elapsed since the date of the 
           closing of the initial placement of the Securities pursuant to the
           Purchase Agreement; and

               (B)  the Securities have been transferred in a transaction 
           permitted by Rule 144 and made in accordance with any applicable
           securities laws of any state of the United States.


                                            G-1-1

<PAGE>

          We understand that this certificate is required in connection with 
certain securities laws of the United States. In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with which this certificate is or would be relevant, we irrevocably authorize
you to produce this certificate to any interested party in such proceeding.
This certificate and the statements contained herein are made for your benefit
and the benefit of the Issuers and the Initial Purchasers.


Dated:  ______________, ____

[Insert Name of Transferor]



By:_____________________________
          Name:
          Title:

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.





                                    G-1-2

<PAGE>

                                  ANNEX G-2

        FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF NON-GLOBAL
      RESTRICTED SECURITY TO PERMANENT REGULATION S GLOBAL SECURITY OR
                   TEMPORARY REGULATION S GLOBAL SECURITY
  (Transfers and exchanges pursuant to Section 305(c)(6) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

          Reference is hereby made to the Indenture, dated as of April 25, 
1996 (the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK
Capital, Inc., as Issuers, and United States Trust Company of New York, as
Trustee. Capitalized terms used but not defined herein shall have the meanings
given to them in the Indenture.

          This letter relates to $___________ principal amount of Restricted
Securities held in definitive form (CUSIP No. _____) by [insert name of
transferor] (the "Transferor"). The Transferor has requested an exchange or
transfer of such Securities.

          In connection with such request and in respect of such Securities, the
Transferor does hereby certify that (i) such Securities are owned by the
Transferor and are being exchanged without transfer or (ii) such transfer has
been effected pursuant to and in accordance with (a) Rule 903 or Rule 904 under
the Securities Act of 1933, as amended (the "Act"), or (b) Rule 144 under the
Act, and accordingly the Transferor does hereby further certify that:

          (1)  if the transfer has been effected pursuant to Rule 903 or Rule
904:

               (A)  the offer of the Securities was not made to a person in the
United States;

               (B)  either:

               (i)  at the time the buy order was originated, the transferee was
          outside the United States or the Transferor and any person acting on
          its behalf reasonably believed that the transferee was outside the
          United States, or

               (ii)  the transaction was executed in, on or through the 
          facilities of a designated offshore securities market and neither
          the Transferor nor any person acting on its behalf knows that the
          transaction was pre-arranged with a buyer in the United States;

               (C)  no directed selling efforts have been made in 
contravention of the requirements of Rule 903 (b) or 904(b) of Regulation S, as
applicable;

               (D)  the transaction is not part of a plan or scheme to evade the
registration requirements of the Act; and 



                                    G-2-1

<PAGE>

               (E) if such transfer is to occur during the Restricted Period, 
upon completion of the transaction, the beneficial interest being transferred
as described above was held with the Depository through [Euroclear] [CEDEL]; or

          (2)  if the transfer has been effected pursuant to Rule 144:

               (A)  more than two years has elapsed since the date of the 
closing of the initial placement of the Securities pursuant to the Purchase
Agreement; and

               (B)  the Securities have been transferred in a transaction 
permitted by Rule 144 and made in accordance with any applicable securities
laws of any state of the United States.

          We understand that this certificate is required in connection with 
certain securities laws of the United States. In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with which this certificate is or would be relevant, we irrevocably authorize
you to produce this certificate to any interested party in such proceeding.
This certificate and the statements contained herein are made for your benefit
and the benefit of the Issuers and the Initial Purchasers.


Dated:  ______________, ____

[Insert Name of Transferor]



By:_____________________________
          Name:
          Title:

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.


                                    G-2-2

<PAGE>

                                  ANNEX H-1

        FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF NON-GLOBAL
        PERMANENT REGULATION S SECURITY TO RESTRICTED GLOBAL SECURITY
  (Transfers and exchanges pursuant to Section 305(c)(7) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

          Reference is hereby made to the Indenture, dated as of April 25, 1996 
(the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK Capital,
Inc., as Issuers, and United States Trust Company of New York, as Trustee. 
Capitalized terms used but not defined herein shall have the meanings given to
them in the Indenture.

          This letter relates to $___________ principal amount of Restricted
Securities held in definitive form (CUSIP No. ____) by [insert name of
transferor] (the "Transferor").  The Transferor has requested an exchange or
transfer of such Securities.

          In connection with such request and in respect of such Securities, the
Transferor does hereby certify that (i) such Securities are owned by the
Transferor and are being exchanged without transfer or (ii) such transfer has
been effected pursuant to and in accordance with Rule 144A under the United
States Securities Act of 1933, as amended, and accordingly the Transferor does
hereby further certify that the Securities are being transferred to a person
that the Transferor reasonably believes is purchasing the Securities for its own
account, or for one or more accounts with respect to which such Person exercises
sole investment discretion, and such Person and each such account is a
"qualified institutional buyer" within the meaning of Rule 144A, in each case in
a transaction meeting the requirements of Rule 144A and in accordance with any
applicable securities laws of any state of the United States.

          We understand that this certificate is required in connection with 
certain securities laws of the United States.  In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with  which this certificate is or would be relevant, we irrevocably authorize 


                                    H-1-1

<PAGE>

you to produce this certificate to any interested party in such proceeding. 
This certificate and the statements contained herein are made for your benefit
and the benefit of the Issuers and the Initial Purchasers.

Dated:  ________________, ____



[Insert Name of Transferor]



By:___________________________
          Name:
          Title:

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital, Inc.


                                    H-1-2

<PAGE>


                                  ANNEX H-2

        FORM OF CERTIFICATION FOR TRANSFER OR EXCHANGE OF NON-GLOBAL
      PERMANENT REGULATION S  SECURITY TO PERMANENT REGULATION S GLOBAL
                                  SECURITY
  (Transfers and exchanges pursuant to Section 305(c)(7) of the Indenture)

United States Trust Company of New York,
   as Trustee
114 West 47th Street
New York, New York 10036.
Attention: Ms. Patricia Stermer

               Re:  NEXTLINK Communications, Inc. and NEXTLINK Capital, INC.
                    12 1/2% Senior Notes Due April 15, 2006 (the "Securities")

          Reference is hereby made to the Indenture, dated as of April 25, 1996 
(the "Indenture"), between NEXTLINK Communications, Inc. and NEXTLINK Capital,
Inc., as Issuers, and United States Trust Company of New York, as Trustee. 
Capitalized terms used but not defined herein shall have the meanings given to
them in the Indenture.

          This letter relates to $___________ principal amount of Restricted
Securities held in definitive form (CUSIP No. ____) by [insert name of
transferor] (the "Transferor").  The Transferor has requested an exchange or
transfer of such Securities.

          In connection with such request and in respect of such Securities, the
Transferor does hereby certify that (i) such Securities are owned by the
Transferor and are being exchanged without transfer or (ii) such transfer has
been effected pursuant to and in accordance with (a) Rule 903 or Rule 904 under
the Securities Act of 1933, as amended (the "Act"), or (b) Rule 144 under the
Act, and accordingly the Transferor does hereby further certify that:

          (1)  if the transfer has been effected pursuant to Rule 903 or Rule 
904:

               (A)  the offer of the Securities was not made to a person in the
United States;

               (B)  either:

               (i)  at the time the buy order was originated, the transferee was
          outside the United States or the Transferor and any person acting on
          its behalf reasonably believed that the transferee was outside the
          United States, or

               (ii)  the transaction was executed in, on or through the 
          facilities of a designated offshore securities market and neither the
          Transferor nor any person acting on its behalf knows that the
          transaction was pre-arranged with a buyer in the United States;

               (C)  no directed selling efforts have been made in 
contravention of the requirements of Rule 903 (b) or 904(b) of Regulation S, as
applicable;

               (D)  the transaction is not part of a plan or scheme to evade the
registration requirements of the Act; and 



                                    H-2-1

<PAGE>

               (E) if such transfer is to occur during the Restricted Period, 
upon completion of the transaction, the beneficial interest being transferred
as described above was held with the Depository through [Euroclear] [CEDEL]; or

          (2)  if the transfer has been effected pursuant torRule 144:

               (A)  more than two years has elapsed since the date of the 
closing of the initial placement of the Securities pursuant to the Purchase
Agreement; and

               (B)  the Securities have been transferred in a transaction 
permitted by Rule 144 and made in accordance with any applicable securities
laws of any state of the United States.

          We understand that this certificate is required in connection with 
certain securities laws of the United States.  In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with  which this certificate is or would be relevant, we irrevocably authorize
you to produce this certificate to any interested party in such proceeding. 
This certificate and the statements contained herein are made for your benefit
and the benefit of the Issuers and the Initial Purchasers.

Dated:  ________________, ____

[Insert Name of Transferor]

By:___________________________
          Name:
          Title:

cc:  NEXTLINK Communications, Inc. and NEXTLINK Capital,rInc.




                                    H-2-2