CONFORMED COPY

                                WAIVER UNDER THE
                              TERM CREDIT AGREEMENT


         WAIVER  dated as of December  1, 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.

                                       W I T N E S S E T H :

         WHEREAS,   the   Borrower  proposes  to  enter  into  the  Restructured
Satellite Business Transactions (as defined below);

         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. In
addition:






         "Restructured  Satellite Business Transactions" means the following and
certain  related  transactions,  each as more fully  described in the Investment
Agreement,  Amended and Restated Motient Services Asset Sale Agreement,  Amended
Research & Development,  Marketing and Service  Agreement,  Limited  Partnership
Agreement,  Amended Registration Rights Agreement,  Amended  Cross-Licensing and
Bulk  Resale   Agreement  and  certain  other  agreements   (collectively,   the
"Transaction  Documents"),  each  substantially in the form delivered to each of
the  Banks  and  Shareholder  Guarantors  prior to  December  1,  2000:  (i) the
conversion of Motient Satellite Ventures LLC into a Delaware limited partnership
("Newco"),  the Borrower's  interest in which may subsequently be transferred to
another new  directly-owned  Subsidiary of the Borrower,  and the formation of a
new corporation to serve as the general partner of Newco, the ownership of which
corporation will mirror the economic  interests held in Newco; (ii) the increase
from 20% to 40% of the aggregate fully diluted ownership interests in Newco held
by Telcom Ventures,  L.L.C.,  Columbia  Capital  Corporation and Spectrum Equity
Investors  LP  or  designated   subsidiaries  or  affiliates  thereof  (each,  a
"Purchaser",  and collectively,  the  "Purchasers",  and the aggregate amount of
such interests held by the  Purchasers,  the "Newco  Purchaser  Interests"),  in
consideration  of the  payment  by the  Purchasers  to Newco of  $50,000,000,  a
portion of which Newco Purchaser Interests, at the option of each Purchaser, may
be exchanged for common  shares of the Borrower;  (iii) the issuance by Newco to
the Purchasers of an option (the "Newco Option"),  which may be exercised by one
or more of the Purchasers, to purchase an additional 10.66% of the fully diluted
ownership  interests in Newco,  exercisable for  $40,000,000  (the "Newco Option
Exercise  Price");  (iv) the  contribution  by TMI  Communications  and Company,
Limited  Partnership  ("TMI")  of  substantially  all  of its  mobile  satellite
business to Newco in exchange  for a cash payment of  $7,500,000,  a note in the
initial  principal amount of $11,500,000 (the "TMI Note") and 27.2% of the fully
diluted  ownership  interests in Newco,  as a result of which the Borrower shall
own less than half of the fully diluted membership  interests of Newco and Newco
shall  thenceforth  cease to be a Subsidiary  of the Borrower or a member of the
Borrower  Group for all purposes  under the Term Credit  Agreement  (even if the
Purchasers later exchange a sufficient  amount of Newco Purchaser  Interests for
common  shares of the Borrower to cause the Borrower to once again own more than
half of the fully diluted  membership  interests of Newco); (v) the execution by
Newco and Motient  Services Inc.  (formerly  AMSC  Subsidiary  Corporation),  an
indirect  wholly-owned  Subsidiary of the Borrower ("Motient  Services"),  of an
amended and restated asset sale agreement  pursuant to which, for a cash payment
to  Motient  Services  of  $45,000,000  of the  $50,000,000  received  from  the
Purchasers  and the  issuance  to  Motient  Services  of a note  in the  initial
principal  amount  of  $15,000,000  (the  "Motient  Services  Note"),  plus  the
$24,000,000  deposit  previously paid to Motient Services,  Newco shall purchase
Motient Services'  satellite  communications  services business (either directly
from  Motient  Services  or by  purchasing  the equity of a new,  directly-owned
Subsidiary  of  Motient   Services  to  which  such  business  shall  have  been
contributed),  pending  the  consummation  of which  purchase  any  proceeds  of
in-orbit  insurance  shall be held in escrow and upon the  consummation of which
purchase any such escrowed proceeds shall be included in the transferred assets;
(vi) the loan by the Borrower to Newco of $2,500,000,  to be evidenced by a note
in the  initial  principal  amount of  $2,500,000,  the  proceeds of which loan,
together with $5,000,000 of the $50,000,000  received from the Purchasers,  will
be used to fund the  $7,5000,000  cash  payment to TMI (such note,  like the TMI
Note and the Motient  Services Note, to have a stated maturity of five years and
interest  accruable at a rate of 10% per annum,  which interest will be added to
principal  semi-annually in arrears, as well as the other terms set forth in the
Transaction Documents); (vii) the formation by the Borrower of one or more other
directly-owned  Subsidiaries,  if necessary  solely to effect an exchange by the
Purchasers  of Newco  Purchaser  Interests  for  common  shares of the  Borrower
(whether  through  a  triangular  merger  of Newco,  such  Subsidiaries  and the
Borrower or otherwise), and the merger of one or more such Subsidiaries with one
or more of the Purchasers or their  transferees;  and (viii) the  performance by
Newco,  Motient  Services,  Motient  Communications  Company and the Borrower of
their respective obligations under the Transaction Documents (including, without
limitation,   obligations   relating   to   indemnification,   the  sharing  and
cross-licensing  of assets and the  disposition  by the  Borrower  (directly  or
through a  transaction  involving  a  Subsidiary)  of its  remaining  membership
interests in Newco in a "drag-along" transaction.

         SECTION 2. Waiver.  The  undersigned  Banks waive  compliance  with the
provisions  of  Article  5 of the  Term  Credit  Agreement  (including,  without
limitation,  Sections 5.04,  5.13, 5.17, 5.18, 5.20 and 5.21) to the extent (and
only to the extent)  necessary  to permit the  Restructured  Satellite  Business
Transactions. The undersigned Banks agree that the purchase of Motient Services'
satellite  communications  services  business  by Newco  (and  none of the other
Restructured Satellite Business Transactions, with the exception of any transfer
or  disposition  by the  Borrower of any portion of its interest in Newco or any
successor  to Newco,  to the extent such  transfer or  disposition  is or may be
contemplated  by the  Restructured  Satellite  Business  Transactions,  and  the
receipt of proceeds of in-orbit insurance,  if the purchase of Motient Services'
satellite  communications business by Newco is not consummated) shall constitute
a Reduction  Event  requiring a prepayment of Loans under Section  2.04(b)(i) to
the extent of any applicable  Net Cash  Proceeds,  with respect to which (x) the
Net Cash  Proceeds  shall  be the sum of  $45,000,000  plus  all  cash  payments
received in respect of the Motient  Services Note,  less any portion  thereof to
which the "Reduction  Percentage" (as defined in the Revolving Credit Agreement)
is applied to the  reduction of the  "Commitments"  (as defined in the Revolving
Credit Agreement), and (y) the Reduction Percentage shall be 50%.

         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 S. Segal
                                    -------------------------------------------
                                    Title: Senior Vice President


                                TORONTO DOMINION (TEXAS), INC.


                                By: /s/ Lynn Chasin
                                    -------------------------------------------
                                    Title: Vice President


                                MORGAN GUARANTY TRUST COMPANY OF NEW YORK


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


                                BANK OF AMERICA, N.A.


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








                                BANCA COMMERCIALE ITALIANA LOS ANGELES FOREIGN
                                 BRANCH


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


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


                                BANCA DI ROMA - SAN FRANCISCO


                                By: /s/ Richard G. Dietz
                                    -------------------------------------------
                                    Title: Vice President


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


                                THE CHASE MANHATTAN BANK


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


                                CITICORP USA, INC.


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





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


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


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


                                BANK ONE, N.A.


                                By: /s/ Stephen C. Price
                                    -------------------------------------------
                                    Title: First Vice President


                                SAN PAOLO IMI S.P.A.


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


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






                                HUGHES ELECTRONICS CORPORATION


                                By: /s/ M. J. Gaines
                                    -------------------------------------------
                                    Title: Corporate Vice President



                                SINGAPORE TELECOMMUNICATIONS LTD.


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



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


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