EXHIBIT 10.35c

                                WAIVER UNDER THE
                           REVOLVING CREDIT AGREEMENT

     WAIVER dated as of June 27, 2000 under the Revolving Credit Agreement dated
as of March 31, 1998 (as heretofore  amended,  the "Revolving Credit Agreement")
among MOTIENT  HOLDINGS INC.  (formerly  AMSC  ACQUISITION  COMPANY,  INC.) (the
"Borrower"),   MOTIENT   CORPORATION   (formerly   AMERICAN   MOBILE   SATELLITE
CORPORATION)  (the "Parent  Guarantor"),  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 Parent Guarantor proposes to enter into the 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 Revolving
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 Revolving Credit Agreement
has the meaning  assigned to such term in the  Revolving  Credit  Agreement.  In
addition:

     "Satellite Business  Transactions" means the following  transactions , each
as more fully  described  in the  Investment  Agreement,  Asset Sale  Agreement,
Research  &  Development,   Marketing  and  Service  Agreement,  LLC  Agreement,
Registration  Rights  Agreement,  Cross-Licensing  and Bulk Resale Agreement and
Parent Transfer Letter Agreement  (collectively,  the "Transaction  Documents"),
each  substantially  in the form delivered to each of the Banks and  Shareholder
Guarantors  prior to June 24, 2000: (i) the formation by the Parent Guarantor of
a new directly-owned Subsidiary,  Motient Satellite Ventures, LLC ("Newco"), the
Parent Guarantor's  interest in which may subsequently be transferred to another
new  directly-owned  Subsidiary  of the Parent  Guarantor;  (ii) the issuance by






Newco to 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"),  in  consideration  of the
payment by the Purchasers to Newco of  $50,000,000,  of membership  interests of
Newco  constituting  20% of the  fully  diluted  membership  interests  of Newco
("Newco  Purchaser  Interests")  which, at the option of each Purchaser,  may be
exchanged for common shares of the Parent Guarantor; (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  40% of the  fully
diluted membership interests of Newco (plus, if fewer than all of the Purchasers
exercise  the  Newco  Option,   such  additional   interests  (the   "Additional
Interests") as are necessary to result in such  Purchasers  collectively  owning
50.1% of the fully  diluted  membership  interests  of Newco),  exercisable  for
$120,000,000 for the first year of the option, increasing by $3,600,000 per full
calendar month during the second and final year of the option, plus an amount to
reflect the sale of any Additional  Interests at the same price per unit that is
paid for the 40% of Newco's  membership  interests  (the "Newco Option  Exercise
Price");  (iv) the exercise of the Newco Option, as a result of which the Parent
Guarantor shall own less than half of the fully diluted membership  interests of
Newco and Newco  shall cease to be a  Subsidiary  of the Parent  Guarantor  or a
member of the Parent  Guarantor  Group;  (v) the  execution by Newco and Motient
Services Inc.  (formerly AMSC  Subsidiary  Corporation),  a direct  wholly-owned
Subsidiary of the Borrower ("Motient  Services"),  of a research and development
and marketing and service  agreement (the "R&D  Agreement")  relating to Motient
Services' satellite  communications  services business,  pursuant to which Newco
shall pay to Motient Services  $20,000,000 of the $50,000,000  received from the
Purchasers  in exchange for access to such business and the right to develop new
business  opportunities  therefor;  (vi)  the  execution  by Newco  and  Motient
Services of an asset sale agreement pursuant to which, for an initial payment to
Motient Services of $24,000,000 of the $50,000,000  received from the Purchasers
and an additional payment to Motient Services equal to the Newco Option Exercise
Price,  Newco  shall  have the right to  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);  (vii) the formation by the
Parent Guarantor 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 Parent Guarantor  (whether  through a triangular  merger of
Newco, such Subsidiaries and the Parent Guarantor or otherwise),  and the merger
of one or more such  Subsidiaries  with one or more of the  Purchasers  or their
transferees;   (viii)  the  performance  by  Newco,  Motient  Services,  Motient
Communications  Company and the Parent Guarantor of their respective obligations
under the Transaction  Documents  (including,  without  limitation,  obligations







relating to  indemnification,  the sharing and  cross-licensing  of assets,  the
disposition by the Parent Guarantor (directly or through a transaction involving
a Subsidiary) of its remaining  membership  interests in Newco in a "drag-along"
transaction,  and the payment by Motient Services to Newco of $44,000,000  under
certain  circumstances and subject to certain conditions relating to the sale by
Motient  Services of its satellite  business to a third party,  the failure of a
satellite or the loss of certain FCC licenses); and (ix) the conversion of Newco
from a limited liability  company to a corporation,  or the liquidation of Newco
in accordance with the terms of the LLC Agreement.

     SECTION  2.  Waiver.  The  undersigned  Banks  waive  compliance  with  the
provisions of Article 5 of the Revolving  Credit Agreement  (including,  without
limitation,  Sections 5.04,  5.12, 5.15, 5.16, 5.18 and 5.19) to the extent (and
only to the extent)  necessary to permit the  Satellite  Business  Transactions.
Subject to the next sentence,  the undersigned  Banks agree that each of (i) the
purchase  by the  Purchasers  of the  Newco  Purchaser  Interests  and  (ii) the
exercise by one or more  Purchasers  of the Newco  Option (and none of the other
Satellite  Business  Transactions,  with the exception of any other  transfer or
disposition  by the Parent  Guarantor 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  Satellite  Business   Transactions)  shall  constitute  a
Reduction Event requiring a reduction of Commitments  under Section  2.09(c)(i),
with respect to which (x) the Net Cash Proceeds shall be $44,000,000 in the case
of the purchase of the Newco Purchaser Interests (the "Newco Purchaser Interests
Reduction  Event") and an amount equal to the Newco Option Exercise Price in the
case of the exercise of the Newco Option and (y) the Reduction  Percentage shall
be 50%.  Finally,  the undersigned Banks agree to waive the requirement that the
Tranche A Commitments  and Tranche C Commitments  be reduced upon the occurrence
of the Newco Purchaser  Interests Reduction Event; as a result, only the Tranche
B Commitments will be reduced upon such occurrence, by $2,750,000.

     SECTION 3.  Representations  of Borrower and Parent Guarantor.  Each of the
Borrower  and  Parent   Guarantor   represents   and   warrants   that  (i)  the
representations  and warranties  set forth in Article 4 of the Revolving  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,  the  Parent
Guarantor,  Hughes, SingTel, Baron Capital and the 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 HOLDINGS INC.
                             (formerly AMSC ACQUISITION COMPANY, INC.)

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


                             MOTIENT CORPORATION
                             (formerly AMERICAN MOBILE SATELLITE CORPORATION)

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


                             TORONTO DOMINION (TEXAS), INC.

                             By:  /s/ Jeffrey R. Lents
                             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/ Charles Dougherty
                             Title: Vice President

                             By:  s/ Frank Maffei
                             Title: Authorized Signature


                             BANCA DI ROMA - SAN FRANCISCO

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

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


                             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/ Robert B. Landis
                             Title: Managing Director


                             BANK ONE, N.A.

                             By:  /s/ Stephanie A. Mack
                             Title:  Commercial Banking Officer


                             SAN PAOLO IMI S.P.A.

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

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





                             HUGHES ELECTRONICS CORPORATION

                             By:  /s/ Mark A. McEachen
                             Title:  Corporate Vice President & Treasurer


                             SINGAPORE TELECOMMUNICATIONS LTD.

                             By:  /s/ Hoh Wing Chee
                             Title: Vice President
                                    International Network


                             BARON CAPITAL
                             PARTNERS, L.P., a
                             Delaware limited partnership


                             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