Exhibit 5.1

                               [Letterhead of Willkie Farr & Gallagher]

June 25, 1998




NEXTLINK Communications, Inc.
155 108th Avenue N.E., 8th Floor
Bellvue, WA 98004




     Re:  $636,974,000 9.45% Senior Discount 
          Notes due 2008 Exchange Offer


Ladies and Gentlemen:

     We have acted as counsel for NEXTLINK Communications, Inc., a Delaware
corporation (the "Company"), in connection with the filing by the Company with
the Securities and Exchange Commission (the "Commission") on June 24, 1998 of a
registration statement (the "Registration Statement") on Form S-4 under the
Securities Act of 1933, as amended, relating to the proposed issuance, in
exchange for $636,974,000 aggregate principal amount of the Company's 9.45%
Senior Discount Notes due 2008 (the "Old Notes"), of $636,974,000 aggregate
principal amount of the Company's 9.45% Senior Notes Discount due 2008 (the "New
Notes").  The New Notes are to be issued pursuant to an Indenture dated as of
April 1, 1998, as supplemented by a First Supplemental Indenture dated as of
June 3, 1998 (the "Indenture"), between the Company and The United States Trust
Company, as trustee (the "Trustee").  Capitalized terms used herein and not
otherwise defined herein have the meanings ascribed thereto in the Indenture or
in the Purchase Agreement, dated as of March 27, 1998, among the Company,
Salomon Brothers Inc and Goldman, Sachs & Co. (the "Initial Purchasers").

     In that connection, we have examined originals, or copies certified or
otherwise identified to our 





satisfaction, of such documents, corporate records and other instruments as we
have deemed necessary or appropriate for purposes of this opinion, including the
Indenture, the Exchange and Registration Rights Agreement, dated as of April 1,
1998 (the "Registration Rights Agreement"), among the Company and the Initial
Purchasers, the form of the New Notes and the Registration Statement.

     In rendering the opinions contained herein, we have assumed (a) the due
authorization, execution and delivery of each of the Indenture, the Registration
Rights Agreement and the New Notes by each of the parties thereto, (b) that each
of such parties has the legal power to act in the respective capacity or
capacities in which it is to act thereunder, (c) the authenticity of all
documents submitted to us as originals, (d) the conformity to the original
documents of all documents submitted to us as copies and (e) the genuineness of
all signatures on all documents submitted to us.

     Based on the foregoing, we are of the opinion that the New Notes, when duly
issued and authenticated in accordance with the provisions of the Indenture and
delivered in exchange for the Old Notes pursuant to the Registration Rights
Agreement, will constitute valid and binding obligations of the Company
enforceable against the Company in accordance with their terms (subject in each
case to applicable bankruptcy, insolvency, reorganization, moratorium,
fraudulent transfer and other similar laws affecting creditors' rights generally
from time to time in effect and to general principles of equity, including,
without limitation, concepts of materiality, reasonableness, good faith and fair
dealing, regardless of whether considered in a proceeding in equity or at law).

     We do not express any opinion with respect to matters governed by any laws
other than the laws of the State of New York and the federal laws of the United
States of America.  

     We know that we may be referred to as counsel who has passed upon the
legality of the issuance of the New Notes on behalf of the Company in the
Registration Statement filed with the Commission, and we hereby consent to such
use of our name in said Registration Statement and to the filing of this opinion
with said Registration Statement as Exhibit 5.1 thereto.

Very truly yours,