Exhibit 99.3


Crown Castle           Crown Castle International Corp.     Tel 713-570.3000
International          510 Bering Drive, Suite 500          Fax 713-570.3100
                       Houston, TX 77057                    www.crown.castle.com

     November 7, 1999


GTE Wireless Incorporated
One GTE Place
MCGA1B3LGL
Alpharetta, Georgia  30004

Re:  Future Tower Contributions

Ladies and Gentlemen:

GTE Wireless Incorporated ("Thrasher"), Crown Castle International Corp.
("Bidder") and certain other entities have entered into a Formation Agreement
dated as of even date herewith (the "Formation Agreement") providing for,
among other things: (i) the formation of three limited liability companies
(collectively, the "Joint Venture") which will acquire, own, operate and
manage communications towers and related assets; (ii) the contribution by
Thrasher (and others) to the Joint Venture of communications towers and
related assets and liabilities; and (iii) the execution by Thrasher (on behalf
of itself and others) and the Joint Venture of a Master Build to Suit
Agreement (the "MBSA") providing for the construction and operation by the
Joint Venture of communications towers upon which Thrasher will locate
communications facilities and pay rents to the Joint Venture (pursuant to the
"Global Lease" (as defined below)); and (iv) the lease of space on certain
towers and related real estate of the Joint Venture pursuant to the terms and
conditions of a Global Lease Agreement to be entered into by Thrasher (on
behalf of itself and others) and the Joint Venture (the "Global Lease") (all
of the foregoing, together with other matters referred to in the Formation
Agreement, collectively herein referred to as the "Transaction" and all of
such documents as the "Transaction Documents"). Capitalized terms used but not
defined herein shall have the meaning assigned to such terms in the Formation
Agreement.

1.   Future Tower Contributions. (a) The parties acknowledge that (i) the
     communications towers and related assets and liabilities to be conveyed
     to the Joint Venture pursuant to the Formation Agreement do not represent
     all of the tower assets currently owned by Thrasher and its affiliates
     (the communications towers and related assets owned by Thrasher (or its
     Affiliates) and not included in the Thrasher Contributed Assets are
     herein referred to as the "Currently Owned Towers"), (ii) Thrasher or its
     affiliates may, in future, acquire additional tower properties in MSA or
     RSA cellular service markets and/or MTA or BTA PCS markets in that
     portion of the United States of America located east of the Mississippi
     river for use in the operation of its cellular system (herein the
     "Subsequently Acquired Towers") and (iii) that an Affiliate of Thrasher,
     GTE Services Incorporated, has acquired approximately 600 additional
     towers and related assets from Ameritech in the Chicago MTA, St. Louis
     MTA and other locations as the result of the SBC- Ameritech merger
     (herein the "Ameritech Towers"). The Ameritech Towers shall not be
     included in the Currently Owned Towers or the Subsequently Acquired
     Towers. Bidder agrees that, notwithstanding anything to the contrary in
     the Transaction Documents, Thrasher (or its Affiliates) shall have the
     right, but not the obligation, to convey (or in the case of the Ameritech
     Towers, to use its







     commercially reasonable efforts to cause to be conveyed) all or any part
     of the Currently Owned Towers, the Subsequently Acquired Towers and the
     Ameritech Towers to the Joint Venture as herein provided or as otherwise
     agreed to by the parties.

     In the event that Thrasher desires to exercise the right to convey (or in
     the case of the Ameritech Towers, to use its commercially reasonable
     efforts to cause to be conveyed) to Bidder any Currently Owned Towers,
     Subsequently Acquired Towers or the Ameritech Towers, Thrasher shall
     provide written notice to Bidder and the Joint Venture. The written
     notice will include a description of such communications towers and
     related assets and liabilities as Thrasher desires to convey (or in the
     case of the Ameritech Towers, to use its commercially reasonable efforts
     to cause to be conveyed) consistent with the information provided by
     Thrasher pursuant to Annexes I, II and III and Section 5.1 of the
     Formation Agreement. Unless otherwise agreed to by the parties, the
     consideration to be received by Thrasher shall be the product of (i) the
     number of such communications towers to be conveyed, multiplied by (ii)
     (x) as to the Currently Owned Towers and the Subsequently Acquired
     Towers, two hundred seventy-five thousand dollars ($275,000) or (y) as to
     the Ameritech Towers, three hundred ninety thousand dollars ($390,000).

     (b)   Unless otherwise agreed to by Thrasher, the consideration will take
     the form of cash (including Incurred Debt) and additional ownership
     interest in HoldCo in the same proportions received by Thrasher under the
     Formation Agreement.

     (c)   Thrasher's rights hereunder to contribute Currently Owned Towers and
     Subsequently Acquired Towers will expire eighteen (18) months after the
     Final Closing. As to the Ameritech Towers, the written notice provided
     for in item (a) above shall apply to all of the Ameritech Towers
     (excluding tower sites with switches or office buildings, if any) and
     must be given by Thrasher not later than May 1, 2000 and the parties
     shall enter into a definitive agreement for the contribution of such
     towers (the "Definitive Agreement") not later than June 30, 2000;
     provided however, Thrasher shall be obligated to cause to be contributed
     to the Joint Venture only such of the Ameritech Towers as to which it has
     obtained all required consents or approvals or is not prohibited from
     making such contribution by the DOJ or otherwise. The time and date for
     the closing of the contribution of the Ameritech Towers shall be
     established by the Definitive Agreement, but in no event shall such
     closing be sooner than June 1, 2000. Upon conveyance of the properties,
     Thrasher (or its Affiliates) will execute Supplements (as defined in the
     Global Lease) for each property conveyed. Any Currently Owned Towers or
     Subsequently Acquired Towers conveyed hereunder will be conveyed subject
     to the same representations and warranties provided for under Section 5.1
     of the Formation Agreement (given as of the date of conveyance) and
     Thrasher, the Joint Venture and the parties to the Formation Agreement
     shall be subject to, and enjoy the benefit of, the indemnification
     provisions set forth in Article 10 of the Formation Agreement; provided,
     however that any time periods provided for in such Article will be deemed
     to commence as of the date of conveyance with respect to the properties
     conveyed pursuant to this letter agreement.

     (d)   Notwithstanding the foregoing, the Joint Venture will not be
     obligated to accept the contribution of more than one hundred (100)
     Currently Owned Towers and Subsequently Acquired Towers, in the
     aggregate, in any twelve (12) month period; provided, however, that if
     the Joint Venture declines to accept at least one hundred (100) of such
     towers in any twelve month period, Thrasher's rights to








     contribute such towers shall be extended until such time as it would be
     able to cause the Joint Venture to accept the contribution of all of such
     towers offered in the eighteen (18) month period following the Final
     Closing. Notwithstanding anything contained herein to the contrary, the
     Joint Venture will be obligated to accept the contribution of no more
     than 600 Ameritech Towers..

     (e)   The provisions of this letter agreement do not apply to the
     conveyance of towers (and related assets and liabilities) by Thrasher
     which were identified on any Annex or Schedule to the Formation
     Agreement, but which were not conveyed at a Closing ("Contemplated
     Towers"). With respect to such Contemplated Towers, the parties agree
     that Thrasher (or the Transferring Entities) will convey such properties
     when and as it is able to and shall receive the consideration in the
     amounts and forms provided for in the Formation Agreement, to the extent
     that such consideration has not already been received by Thrasher.

     (f)   Notwithstanding the foregoing, with regard to the Ameritech Towers,
     in addition to the right of Thrasher to cause the contribution of those
     towers to the Joint Venture, the Joint Venture shall have the right to
     require that all, but not less than all, of those towers (excluding tower
     sites with switches or office buildings, if any) be contributed to the
     Joint Venture which right shall be exercised by written notice from the
     Joint Venture to Thrasher not later than May 1, 2000 and the parties
     shall enter into the Definitive Agreement not later than June 30, 2000;
     provided however, Thrasher shall be obligated to cause to be contributed
     to the Joint Venture only such of the Ameritech Towers as to which it has
     obtained all required consents or approvals or is not prohibited from
     making such contribution by the DOJ or otherwise., The time and date for
     the closing of the contribution of the Ameritech Towers will be
     established by the Definitive Agreement, but in no event shall such
     closing be sooner than June 1, 2000. Upon receipt of such notice Thrasher
     will prepare a description of such communications towers and related
     assets and liabilities consistent with the information provided by
     Thrasher pursuant to Annexes I, II and III and Section 5.1 of the
     Formation Agreement and the consideration to be received by Thrasher
     shall be the product of (i) the number of such communications towers to
     be conveyed, multiplied by (ii) three hundred ninety thousand dollars
     ($390,000)

     (g)   All towers contributed by Thrasher or its Affiliates to the Joint
     Venture under this letter agreement shall be included as a part of the
     buildings, towers, and facilities of the Joint Venture that are subject
     to the Global Lease and, as such, will be subject to the terms and
     conditions of the Global Lease; as to each contributed tower, Thrasher
     and Bidder will execute and deliver, each to the other, a Supplement (as
     defined in the Global Lease). Unless otherwise agreed to by Thrasher, the
     consideration will take the form of cash and additional ownership
     interest in HoldCo in the same proportions received by Thrasher under the
     Formation Agreement.

     (h)   The Definitive Agreement shall (i) include, without limitation, the
     terms of Article 7 of the Formation Agreement (as modified to accommodate
     the time and circumstances applicable to the closing of the Currently
     Owned Towers, the Subsequently Acquired Towers and the Ameritech Towers)
     and (ii) provide that any obligation of Thrasher to obtain the Required
     Thrasher Phase I Reports with regard to the Subsequently Acquired Towers
     and the Ameritech Towers shall be determined by the date of the
     acquisition of those towers by the party from which Thrasher or its
     Affiliate obtained them and not by the date such towers were acquired by
     Thrasher or its Affiliate.









2.   Miscellaneous.

     (a)   All notices hereunder must be in writing and shall be deemed validly
     given if sent in accordance with the provisions of Section 11.9 of the
     Formation Agreement.

     (b)   This letter agreement shall be governed by and interpreted and
     enforced in accordance with the laws of the State of Delaware, without
     regard to the principles of conflict of law thereof.

     (c)   This letter agreement may be executed in multiple counterparts and
     any party hereto may execute any such counterpart, each of which when
     executed and delivered shall be deemed to be an original and all of which
     counterparts taken together shall constitute but one and the same
     instrument. This letter agreement shall become binding when one or more
     counterparts taken together shall have been executed and delivered by the
     parties.

     (d)   Any dispute hereunder shall be resolved in the manner set forth in
     Section 11.1 of the Formation Agreement.

     (e)   This letter agreement may not be assigned by any party hereto without
     the prior written consent of the other party, provided that (i) Thrasher
     may assign its rights hereunder to any entity of which either Thrasher
     Parent, Thrasher or Bell Atlantic (after the Bell Atlantic/Thrasher
     Merger is consummated) owns directly or indirectly a majority of the
     voting power of the outstanding capital stock or to any transferee of its
     entire remaining Thrasher HoldCo Interest, in each case, in compliance
     with Section 9.2 of the Formation Agreement, and (ii) Bidder may assign
     any of its rights hereunder to any wholly-owned (direct or indirect)
     subsidiary of Bidder or to any transferee of its entire remaining Bidder
     HoldCo Interest, in each case, in compliance with Section 9.1 of the
     Formation Agreement. No such assignment shall relieve Thrasher or Bidder
     of their respective obligations hereunder except that in connection with
     a transfer by Thrasher of its entire remaining Thrasher HoldCo Interest,
     respectively, made in accordance with the provisions of Article 9 of the
     Formation Agreement, the transferring party shall be relieved only of its
     obligations under Articles 8 and 9 of the Formation Agreement. For
     purposes of the foregoing, a transfer by merger by Bidder or Thrasher
     (whether or not Bidder or Thrasher is the surviving corporation), or any
     direct or indirect parent corporation of Bidder or Thrasher, shall not be
     deemed to be an assignment for purposes of this letter agreement. Subject
     to the foregoing, all of the terms and provisions of this Agreement shall
     be binding upon and inure to the benefit of and be enforceable by the
     permitted successors and assigns of Thrasher and Bidder. All references
     herein to any party shall be deemed to include any successor to such
     party, including any corporate successor.

     (f)   This letter agreement shall automatically terminate upon the
     termination of the Formation Agreement, including the circumstance where
     one or more Closings have occurred and the Formation Agreement and the
     other Transaction Documents remain in effect for the limited purpose of
     governing the parties' relationship with respect to the assets and
     liabilities transferred and assumed at such Closings.

     (g)   The parties understand and agree that in no event may the Thrasher
     HoldCo Interest be decreased to a percentage less than 10.0% (assuming
     that no Bidder Contributed Shares have been contributed to or are held by
     HoldCo) as a result of







     adjustments in the percentage interests of the members of HoldCo and,
     accordingly, to the extent that any of the transactions contemplated
     hereby would cause such decrease to occur the parties will revise the
     terms of the transactions contemplated in order to prevent such decrease.

          The foregoing represents the entire agreement of the parties with
respect to the matters expressly provided for herein, and except as expressly
provided for herein, shall not be deemed to amend, alter, modify or waive any
of the rights or obligations of the parties under the Formation Agreement or
any other Transaction Documents.









          Please execute the enclosed copy of this letter and return it to the
address set forth above, evidencing Thrasher's agreement to the terms and
conditions of this letter. Execution of the letter by each of us shall
constitute each parties agreement to the foregoing and each party agrees to
use its best efforts to cause the Joint Venture to comply with any of its
obligations hereunder.

                                               CROWN CASTLE INTERNATIONAL
                                               CORP.

                                               By: __________________________
                                               Name: ________________________
                                               Title__________________________

                                               GTE WIRELESS INCORPORATED

                                               By: __________________________
                                               Name: ________________________
                                               Title__________________________