CONFORMED COPY

                                   ASSET SALE
                                WAIVER UNDER THE
                              TERM CREDIT AGREEMENT


         WAIVER  dated as of October 20,  2000 under the Term  Credit  Agreement
dated as of March 31, 1998 (as heretofore amended,  the "Term Credit Agreement")
among MOTIENT CORPORATION (formerly AMERICAN MOBILE SATELLITE  CORPORATION) (the
"Borrower"),  the BANKS party  thereto  (the  "Banks"),  MORGAN  GUARANTY  TRUST
COMPANY OF NEW YORK, as Documentation  Agent (the  "Documentation  Agent"),  and
TORONTO DOMINION  (TEXAS),  INC., as Administrative  Agent (the  "Administrative
Agent").

                              W I T N E S S E T H :







         WHEREAS,  (i) Motient Holdings Inc. (formerly AMSC Acquisition Company,
Inc.) ("Holdings"),  a direct wholly-owned subsidiary of the Borrower,  proposes
(x) to sell certain assets used in connection  with the wireless  communications
business  for the  transportation  industry  to  Aether  Systems  Inc.  for cash
consideration  of up to  $52,500,000  ($20,000,000  to be  received  at closing,
$10,000,000 to be received upon satisfaction of certain  conditions  relating to
the MobileMax 2 product,  and up to the  remaining  $22,500,000  (the  "Earn-out
Payment") to be received in March, 2002 if certain performance criteria are met)
(the "Retail  Transportation  Business Sale"), 100% of the Net Cash Proceeds (as
defined  in the Term  Credit  Agreement)  of which  will be  applied  to  reduce
commitments and, if applicable, repay loans in accordance with the provisions of
Holdings'  revolving credit agreement  (provided that if the Earn-out Payment is
received  after  (1)  the   consummation   of  the  transfer  of  the  satellite
communications  business of Motient  Services Inc., as contemplated by the asset
purchase agreement (the "Asset Purchase Agreement")  described in clause (vi) of
the definition of Satellite Business  Transactions set forth in the Waiver dated
as of June 27, 2000 under the Term Credit Agreement (the "June Waiver"), and (2)
application  of an amount equal to the Net Cash  Proceeds of the exercise of the
Newco  Option (as  defined in the June  Waiver) to reduce  commitments  and,  if
applicable, repay loans in accordance with the provisions of Holdings' revolving
credit  agreement and clause (ii) below,  then only 75% of the Net Cash Proceeds
of the  Earn-out  Payment  shall be so  applied);  and (y) to enter into related
agreements,  including,  without  limitation,  an intellectual  property license
agreement,  an inventory  purchase  agreement,  a terrestrial  network  reseller
agreement,   a  network  satellite  services  agreement  and  a  service  bureau
agreement,  none of the  proceeds of which will be applied to prepay loans under
the Term Credit  Agreement or to reduce  commitments  under Holdings'  revolving
credit  agreement;  and (ii) as a result of the Retail  Transportation  Business
Sale, the additional  amount payable to Motient  Services Inc. for its satellite
communications  services  business  under the Asset  Purchase  Agreement will be
reduced by the sum of $39,500,000 plus one-half of any Earn-out Payment, and for
purposes of Section 2 of the June Waiver the Net Cash  Proceeds of the  exercise
of the Newco Option shall be reduced by a like amount (the  "Satellite  Business
Transactions Modification"); and

         WHEREAS,  the  undersigned  Banks and the  Shareholder  Guarantors  are
willing to consent to the foregoing and to waive certain  provisions of the Term
Credit Agreement in connection with the foregoing;

         NOW, THEREFORE, the undersigned parties hereto agree as follows:

         SECTION  1.  Definitions;  References.  Unless  otherwise  specifically
defined  herein,  each term used  herein  which is  defined  in the Term  Credit
Agreement has the meaning assigned to such term in the Term Credit Agreement.

         SECTION 2. Waiver.  The  undersigned  Banks waive  compliance  with the
provisions  of Sections  5.04(a) and 5.18 of the Term  Credit  Agreement  to the
extent (and only to the extent) necessary to permit the transactions referred to
in clause (i) of the first recital above.  In addition,  the  undersigned  Banks
consent to the Satellite  Business  Transactions  Modification and deem the June
Waiver to have been amended to the extent necessary to give effect thereto.

         SECTION 3.  Representations  of Borrower.  The Borrower  represents and
warrants that (i) the  representations  and warranties set forth in Article 4 of
the Term Credit Agreement shall be true on and as of the Effective Date and (ii)
no Default shall have occurred and be continuing on such date.

         SECTION  4.   Governing  Law.  This  Waiver  shall be  governed  by and
construed in accordance with the laws of the State of New York.

         SECTION  5.  Counterparts.  This  Waiver may be signed in any number of
counterparts, each of which shall be an original, with the same effect as if the
signatures thereto and hereto were upon the same instrument.






         SECTION 6. Effectiveness.  This Waiver shall become effective as of the
date  hereof on the date (the  "Effective  Date") when the  Documentation  Agent
shall have  received a  counterpart  hereof from each of the  Borrower,  Hughes,
SingTel,  Baron  Capital  and the  Required  Banks  signed  by such  party  or a
facsimile  or  other  written   confirmation   (in  form   satisfactory  to  the
Documentation Agent) that such party has signed a counterpart hereof.

         SECTION 7.  Shareholder  Guarantor Consent. The Shareholder  Guarantors
consent to the foregoing.







         IN WITNESS  WHEREOF,  the parties  hereto have caused this Waiver to be
duly executed as of the date first above written.



                                MOTIENT CORPORATION (formerly
                                AMERICAN MOBILE SATELLITE CORPORATION)


                                By: /s/ Randy Segal
                                    -------------------------------------------
                                    Name: Randy Segal
                                    Title:   Senior Vice President


                                TORONTO DOMINION (TEXAS), INC.


                                By: /s/ Jano Mott
                                    -------------------------------------------
                                    Name: Jano Mott
                                    Title:   Vice President


                                MORGAN GUARANTY TRUST COMPANY OF NEW YORK


                                By: /s/ Robert Bottamedi
                                    -------------------------------------------
                                    Name: Robert Bottamedi
                                    Title:   Vice President


                                BANK OF AMERICA, N.A.


                                By: /s/ Dianne J. Prust
                                    -------------------------------------------
                                    Name: Dianne J. Prust
                                    Title:   Principal






                                BANCA COMMERCIALE ITALIANA LOS ANGELES FOREIGN
                                 BRANCH


                                By: /s/ Frank Maffei
                                    -------------------------------------------
                                    Name: Frank Maffei
                                    Title:   Vice President


                                By: /s/ Charles Dougherty
                                    -------------------------------------------
                                    Name:  Charles Dougherty
                                    Title:    Vice President


                                BANCA DI ROMA - SAN FRANCISCO


                                By: /s/ Luca Balestra
                                    -------------------------------------------
                                    Name: Luca Balestra
                                    Title:   Senior Vice President & Manager


                                By: /s/ Thomas C. Woodruff
                                    -------------------------------------------
                                    Name: Thomas C. Woodruff
                                    Title:   Vice President


                                THE CHASE MANHATTAN BANK


                                By: /s/ Tracey Navin Ewing
                                    -------------------------------------------
                                    Name:  Tracey Navin Ewing
                                    Title:    Vice President


                                CITICORP USA, INC.


                                By: /s/ Walter L. Larsen
                                    -------------------------------------------
                                    Name: Walter L. Larsen
                                    Title:   Managing Director






                                DEUTSCHE BANK AG, NEW YORK BRANCH AND/OR CAYMAN
                                 ISLANDS BRANCH


                                By: /s/ Virginia Mahler Cosenza
                                    -------------------------------------------
                                    Name: Virginia Mahler Consenza
                                    Title:   Vice President


                                By: /s/ Andreas Neumeier
                                    -------------------------------------------
                                    Name: Andreas Neumeier
                                    Title:   Vice President



                                BANK ONE, N.A.


                                By: /s/ Stephanie S. Mack
                                    -------------------------------------------
                                    Name: Stephanie S. Mack
                                    Title:   Commercial Banking Officer



                                SAN PAOLO IMI S.P.A.


                                By: /s/ Carlo Persico
                                    -------------------------------------------
                                    Name: Carlo Persico
                                    Title:   Deputy General Manager


                                By: /s/ Robert Wurster
                                    -------------------------------------------
                                    Name: Robert Wurster
                                    Title:   1st Vice President





                                HUGHES ELECTRONICS CORPORATION


                                By: /s/ Michael Gaines
                                    -------------------------------------------
                                    Name: Michael Gaines
                                    Title:   Corporate Vice President


                                SINGAPORE TELECOMMUNICATIONS LTD.


                                By: /s/ Tay Chek Khoon
                                    -------------------------------------------
                                    Name: Tay Chek Khoon
                                    Title:   Managing Director
                                             Satellite Business Group

                                BARON CAPITAL PARTNERS, L.P., a Delaware limited
                                 partnership
                                By: BARON CAPITAL MANAGEMENT, INC., a general
                                 partner


                                By: /s/ Linda S. Martinson
                                    -------------------------------------------
                                    Name: Linda S. Martinson
                                    Title:   Vice President & General Counsel