CONFORMED COPY

                                   STOCK SALE
                                WAIVER UNDER THE
                              TERM CREDIT AGREEMENT



         WAIVER  dated as of February  9, 2001 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.

                              W I T N E S S E T H :

         WHEREAS,  on February 9, 2001 the  Borrower  sold  1,000,000  shares of
Class A common stock of XM Satellite  Radio Holdings Inc. as contemplated by the
Stock Sale Waiver dated as of October 18, 2000 (the "October 2000 Waiver"),  for
Net Cash Proceeds (as defined in the Term Credit Agreement) of $16,499,450,  and
proposes  to  retain  all  (instead  of 50%) of the Net  Cash  Proceeds  of such
transaction,  and not to apply any portion  thereof to prepay loans  outstanding
under the Term Credit Agreement; and

         WHEREAS,  the  undersigned  Banks and the  Shareholder  Guarantors  are
willing to consent to the  foregoing and to modify the terms of the October 2000
Waiver to give effect thereto;

         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 Section 2.04(b)(i) of the Term Credit Agreement to the extent (and
only to the extent) necessary to permit the transaction referred to in the first
recital above, it being understood that all other provisions of the October 2000
Waiver remain in full force and effect with respect to such transaction.






                                        2

         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/ Lynn Chasin
                                               ---------------------------------
                                                 Name: Lynn Chasin
                                                 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:
                                               ---------------------------------
                                                 Name:
                                                 Title:








                                          BANCA COMMERCIALE ITALIANA
                                                LOS ANGELES FOREIGN BRANCH


                                            By:
                                               ---------------------------------
                                                 Name:
                                                 Title:


                                            By:
                                                --------------------------------
                                                 Name:
                                                 Title:


                                          BANCA DI ROMA - SAN FRANCISCO


                                            By:
                                               ---------------------------------
                                                 Name:
                                                 Title:


                                            By:
                                               ---------------------------------
                                                 Name:
                                                 Title:


                                          THE CHASE MANHATTAN BANK


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


                                          CITICORP USA, INC.


                                            By:/s/ Walt Larsen
                                               ---------------------------------
                                                 Name: Walt Larsen
                                                 Title:    Managing Director








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


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


                                            By:/s/ Andreas Neumeier
                                               ---------------------------------
                                                 Name: Andreas Neumeier
                                                 Title:   Director


                                          BANK ONE, N.A.


                                            By:/s/ Karen C. Ryan
                                               ---------------------------------
                                                 Name: Karen C. Ryan
                                                 Title:   Vice President


                                          SANPAOLO IMI S.P.A.


                                            By:
                                               ---------------------------------
                                                 Name:
                                                 Title:


                                            By:
                                               ---------------------------------
                                                 Name:
                                                 Title:








                                          HUGHES ELECTRONICS CORPORATION


                                            By:/s/ David J. Mitchell
                                               ---------------------------------
                                                 Name: David J. Mitchell
                                                 Title:   Assistant Treasurer


                                          SINGAPORE TELECOMMUNICATIONS LTD.


                                            By:/s/ Tay Chek Khoon
                                               ---------------------------------
                                                 Name: Tay Chek Khoon
                                                 Title:   Vice Presidents



                                          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