EXHIBIT 10.72

                                                               [EXECUTION COPY]





                                  $100,000,000


                              TERM CREDIT AGREEMENT


                                   dated as of


                                 March 31, 1998



                                      among


                     American Mobile Satellite Corporation,


                            The Banks Listed Herein,


                   Morgan Guaranty Trust Company of New York,
                             as Documentation Agent,


                                       and


                         Toronto Dominion (Texas), Inc.,
                             as Administrative Agent








                                                                          PAGE

                                TABLE OF CONTENTS

                             ----------------------

                                                                          PAGE

                                    ARTICLE 1
                                   DEFINITIONS

SECTION 1.01.  Definitions...................................................1
SECTION 1.02.  Accounting Terms and Determinations..........................20

                                    ARTICLE 2
                                   THE CREDITS

SECTION 2.01.  Commitments to Lend..........................................21
SECTION 2.02.  Method of Borrowing..........................................21
SECTION 2.03.  Notes........................................................22
SECTION 2.04.  Maturity of Loans; Mandatory Prepayments.....................23
SECTION 2.05.  Interest Rates...............................................24
SECTION 2.06.  Method of Electing Interest Rates............................25
SECTION 2.07.  Mandatory Termination and Reduction of Commitments...........27
SECTION 2.08.  Optional Prepayments.........................................27
SECTION 2.09.  General Provisions as to Payments............................28
SECTION 2.10.  Funding Losses...............................................28
SECTION 2.11.  Computation of Interest and Fees.............................29
SECTION 2.12.  Extension of Maturity Date...................................29

                                    ARTICLE 3
                                   CONDITIONS

SECTION 3.01.  Closing......................................................29
SECTION 3.02.  Borrowings...................................................32

                                    ARTICLE 4
                         REPRESENTATIONS AND WARRANTIES

SECTION 4.01.  Corporate Existence and Power................................33
SECTION 4.02.  Corporate Authorization; No Contravention....................33
SECTION 4.03.  Government Approvals.........................................33
SECTION 4.04.  Binding Effect...............................................34
SECTION 4.05.  Litigation...................................................34
SECTION 4.06.  No Default...................................................34




                                        i




                                                                          PAGE

SECTION 4.07.  ERISA Compliance.............................................34
SECTION 4.08.  Title to Property............................................36
SECTION 4.09.  Taxes........................................................36
SECTION 4.10.  Financial Condition..........................................36
SECTION 4.11.  Environmental Matters........................................37
SECTION 4.12.  Regulated Entities...........................................37
SECTION 4.13.  Subsidiaries.................................................37
SECTION 4.14.  Insurance....................................................37
SECTION 4.15.  Business.....................................................38
SECTION 4.16.  Collateral; Property.........................................38
SECTION 4.17.  Security and Pledge Agreement................................38
SECTION 4.18.  Disclosure...................................................38

                                    ARTICLE 5
                                    COVENANTS

SECTION 5.01.  Information..................................................39
SECTION 5.02.  Certificates; Other Information..............................40
SECTION 5.03.  Notices......................................................40
SECTION 5.04.  Conduct of Business; Preservation of Corporate Existence.....42
SECTION 5.05.  Maintenance of Property......................................42
SECTION 5.06.  Maintenance of Insurance.....................................42
SECTION 5.07.  Payment of Obligations.......................................43
SECTION 5.08.  Compliance with Laws.........................................43
SECTION 5.09.  Inspection of Property and Books and Records.................43
SECTION 5.10.  Environmental Laws...........................................44
SECTION 5.11.  Use of Proceeds..............................................44
SECTION 5.12.  Security and Pledge Agreement................................44
SECTION 5.13.  No Subsidiaries..............................................44
SECTION 5.14.  FCC Approval.................................................44
SECTION 5.15.  Government Approvals.........................................45
SECTION 5.16.  Further Assurances...........................................45
SECTION 5.17.  Limitation on Liens..........................................46
SECTION 5.18.  Disposition of Assets, Consolidations and Mergers............47
SECTION 5.19.  Employee Contracts and Arrangements..........................49
SECTION 5.20.  Investments..................................................49
SECTION 5.21.  Transactions with Affiliates.................................49
SECTION 5.22.  Compliance with ERISA........................................49
SECTION 5.23.  Restricted Payments..........................................50




                                       ii




                                                                          PAGE

SECTION 5.24.  Accounting Changes...........................................50
SECTION 5.25.  Limitation on Indebtedness...................................50

                                    ARTICLE 6
                                    DEFAULTS

SECTION 6.01.  Events of Default............................................51
SECTION 6.02.  Notice of Default............................................56

                                    ARTICLE 7
                                   THE AGENTS

SECTION 7.01.  Appointment and Authorization................................56
SECTION 7.02.  Agents and Affiliates........................................56
SECTION 7.03.  Action by Agents.............................................56
SECTION 7.04.  Consultation with Experts....................................56
SECTION 7.05.  Liability of Agents..........................................57
SECTION 7.06.  Indemnification..............................................57
SECTION 7.07.  Credit Decision..............................................57
SECTION 7.08.  Successor Agent..............................................57
SECTION 7.09.  Agents' Fees.................................................58

                                    ARTICLE 8
                             CHANGE IN CIRCUMSTANCES

SECTION 8.01.  Basis for Determining Interest Rate Inadequate or Unfair.....58
SECTION 8.02.  Illegality...................................................59
SECTION 8.03.  Increased Cost and Reduced Return............................59
SECTION 8.04.  Taxes........................................................61
SECTION 8.05.  Base Rate Loans Substituted for Affected Euro-Dollar
               Loans........................................................63

                                    ARTICLE 9
                                  MISCELLANEOUS

SECTION 9.01.  Notices......................................................63
SECTION 9.02.  No Waivers...................................................64
SECTION 9.03.  Expenses; Indemnification....................................64
SECTION 9.04.  Sharing of Set-offs..........................................64




                                       iii




                                                                          PAGE

SECTION 9.05.  Amendments and Waivers.......................................65
SECTION 9.06.  Successors and Assigns.......................................65
SECTION 9.07.  Collateral...................................................67
SECTION 9.08.  Governing Law; Submission to Jurisdiction....................67
SECTION 9.09.  Counterparts; Integration; Effectiveness.....................68
SECTION 9.10.  Waiver of Jury Trial.........................................68
SECTION 9.11.  Confidentiality..............................................68

COMMITMENT SCHEDULE
PRICING SCHEDULE
DISCLOSURE SCHEDULE
EXHIBIT A - Note
EXHIBIT B - Opinion of Counsel for the  Borrower  
EXHIBIT C - Opinion of Special Counsel for the Agents 
EXHIBIT D - Assignment and Assumption Agreement





                                       iv





                              TERM CREDIT AGREEMENT


         AGREEMENT  dated as of March 31, 1998 among AMERICAN  MOBILE  SATELLITE
CORPORATION,  the BANKS listed on the signature  pages hereof,  MORGAN  GUARANTY
TRUST COMPANY OF NEW YORK, as Documentation Agent, and TORONTO DOMINION (TEXAS),
INC., as Administrative Agent.

         The parties hereto agree as follows:



                                    ARTICLE 1
                                   DEFINITIONS

          SECTION 1.01.  Definitions.  The following terms, as used herein, have
the following meanings:

         "ACTEL" means African Continental Telecommunications Ltd.

         "ACTEL   Agreement"   means  the   agreement   among  AMSC   Subsidiary
Corporation,  the Borrower and ACTEL, dated as of December 2, 1997,  pursuant to
which AMSC Acquisition will lease its MSAT-2 Satellite to ACTEL, as in effect on
the Effective Date.

         "Acquisition" means the acquisition by AMSC Acquisition Company of 100%
of the capital  stock or other equity  interests of ARDIS  pursuant to the ARDIS
Purchase Agreement.

         "Adjusted London Interbank Offered Rate" has the meaning set forth in
Section 2.05(b).

          "Administrative  Agent" means Toronto  Dominion  (Texas),  Inc. in its
capacity as administrative agent for the Banks hereunder,  and its successors in
such capacity.

         "Administrative  Questionnaire"  means,  with respect to each Bank,  an
administrative  questionnaire in the form prepared by the  Administrative  Agent
and submitted to the  Administrative  Agent (with a copy to the  Borrower)  duly
completed by such Bank.




                                        1





         "Affiliate" means, as to any Person,  any other Person which,  directly
or  indirectly,  is in control of, is controlled  by, or is under common control
with,  such Person.  A Person shall be deemed to control  another  Person if the
controlling  Person  possesses,  directly or indirectly,  the power to direct or
cause the direction of the management and policies of the other Person,  whether
through the ownership of voting  securities,  by contract or otherwise.  Without
limitation,  any director,  executive officer or beneficial owner of 25% or more
of the equity of a Person shall,  for the purposes of this Agreement,  be deemed
to control the other Person,  and each Shareholder  Guarantor shall be deemed to
be an Affiliate.

         "Agents" means the  Administrative  Agent and the Documentation  Agent,
and "Agent" means either of the foregoing.

         "AMRC Holdings" means AMRC Holdings, Inc., a Delaware corporation,
and its successors

         "AMSC  Acquisition  Company" means AMSC  Acquisition  Company,  Inc., a
Delaware corporation, and its successors.

         "Applicable Lending Office" means, with respect to any Bank, (i) in the
case of its Base Rate Loans, its Domestic Lending Office and (ii) in the case of
its Euro-Dollar Loans, its Euro-Dollar Lending Office.

         "ARDIS"  means,  collectively,  Motorola  ARDIS  Acquisition,  Inc.,  a
Delaware  corporation,  Motorola  ARDIS,  Inc.,  a Delaware  corporation,  ARDIS
Holding  Company,  a New York general  partnership,  Radio Data Network  Holding
Corporation,  a Delaware  corporation,  and ARDIS  Company,  a New York  general
partnership.

         "ARDIS Purchase  Agreement" means the Stock Purchase Agreement dated as
of December 31, 1997 among the  Borrower,  AMSC  Acquisition  Company,  Motorola
Inc., Motorola ARDIS Acquisition, Inc. and Motorola ARDIS, Inc.

         "Asset Sale" means any sale, lease or other disposition  (including any
such transaction  effected by way of merger or  consolidation  and the Satellite
Lease  Arrangements)  by the Borrower or any of its  Subsidiaries  of any asset,
including  without  limitation any  sale-leaseback  transaction,  whether or not
involving a capital lease,  but excluding (i)  dispositions of inventory,  cash,
cash equivalents and other cash management  investments and obsolete,  unused or
unnecessary  equipment and undeveloped real estate, in each case in the ordinary
course of business and (ii)  dispositions to the Borrower or a Subsidiary of the
Borrower.




                                        2





         "Assignee" has the meaning set forth in Section 9.06(c).

         "Bank"  means each bank  listed on the  signature  pages  hereof,  each
Assignee which becomes a Bank pursuant to Section 9.06(c),  and their respective
successors.

         "Baron Capital" means Baron Capital Partners,  L.P., a Delaware limited
partnership.

         "Baron  Capital  Guaranty"  means the  Guaranty,  dated as of March 31,
1998, made by Baron Capital to the Administrative  Agent for its own benefit and
the benefit of the Banks, as the same may be amended from time to time.

         "Baron Capital Letter of Credit" means the Letter of Credit dated March
31, 1998 issued by The Bank of New York for the account of Baron Capital for the
benefit of the Administrative Agent on behalf of the Banks.

         "Base Rate" means, for any day, a rate per annum equal to the higher of
(i) the Prime  Rate for such day and (ii) the sum of 5/8 of 1% plus the  Federal
Funds Rate for such day.

         "Base Rate Loan" means (i) a Loan which bears interest at the Base Rate
pursuant  to the  applicable  Notice of  Borrowing  or Notice of  Interest  Rate
Election or the  provisions  of Article 8 or (ii) an overdue  amount which was a
Base Rate Loan immediately before it became overdue.

         "Borrower" means American Mobile Satellite Corporation, a Delaware
corporation, and its successors.

         "Borrower Group" means the Borrower and its Consolidated Subsidiaries.

         "Borrowing" means a borrowing hereunder consisting of Loans made to the
Borrower  on the same day  pursuant  to Article 2, all of which Loans are of the
same Type  (subject  to Article 8) and,  except in the case of Base Rate  Loans,
have the same initial Interest Period. A Borrowing is a "Base Rate Borrowing" if
such Loans are Base Rate Loans or a  "Euro-Dollar  Borrowing"  if such Loans are
Euro-Dollar Loans.

         "Capital Lease Obligations" means all monetary  obligations of a Person
under any leasing or similar  arrangement  which,  in  accordance  with GAAP, is
classified as a capital lease.

         "Cash Equivalents" means:




                                        3





          (a)  securities  issued or fully  guaranteed  or insured by the United
States  Government or any agency thereof and backed by the full faith and credit
of the United States  having  maturities of not more than twelve months from the
date of acquisition;

          (b) certificates of deposit, time deposits,  Eurodollar time deposits,
or bankers' acceptances having in each case a tenor of not more than six months,
issued by any Bank, or by any U.S.  commercial bank having combined  capital and
surplus of not less than $500,000,000 whose short term securities are rated both
A-1 or higher by  Standard  & Poor's  Corporation  and P-1 or higher by  Moody's
Investors Services, Inc.;

          (c)  commercial  paper of an  issuer  rated  either  at  least  A-1 by
Standard & Poor's Ratings Group, a division of  McGraw-Hill,  Inc. and/or P-1 by
Moody's  Investors  Service  Inc.  and in either case having a tenor of not more
than three months;

          (d) repurchase agreements fully collateralized by securities issued by
United States Government agencies; and

          (e) money market mutual funds invested in the instruments permitted by
clauses (a), (b), (c) and (d) above.

         "CERCLA" has the meaning specified in the definition "Environmental
Laws".

         "Change In  Control"  means (i) any person or group of persons  (within
the  meaning of  Section 13 or 14 of the  Securities  Exchange  Act of 1934,  as
amended) (other than any Shareholder Guarantor,  AT&T Wireless Services, Inc. or
Motorola,  Inc.)  shall have  beneficial  ownership  (within the meaning of Rule
13d-3  promulgated by the Securities and Exchange  Commission under said Act) of
more than 25% of the  outstanding  capital  stock of the  Borrower,  (ii) Hughes
shall have  beneficial  ownership  of less than 25% of the  outstanding  capital
stock of the  Borrower,  except solely as a result of the issuance of additional
capital  stock by the  Borrower to Persons  other than  Hughes,  in which case a
Change of Control  under this clause (ii) shall not occur  unless  Hughes  shall
have beneficial  ownership of less than 10% of the outstanding  capital stock of
the  Borrower,  (iii)  during  any  period of 24  consecutive  calendar  months,
individuals  who were  directors of the Borrower on the first day of such period
shall cease to  constitute  a majority of the board of directors of the Borrower
(ignoring for this purpose replacements of  stockholder-designated  directors by
successor directors designated by the same stockholder or group of stockholders)
or (iv) the Borrower shall cease to own all of the outstanding  capital stock of
AMSC Acquisition Company.




                                        4





         "Closing  Date" means the date on or after the Effective  Date on which
the  Documentation  Agent shall have  received  the  documents  specified  in or
pursuant to Section 3.01(a).

         "Code" means the Internal Revenue Code of 1986, as amended, or any
successor statute.

         "Collateral" means all property with respect to which Liens are created
or purported to be created pursuant to the Security and Pledge Agreement.

         "Commitment"  means any Tranche A  Commitment,  Tranche B Commitment or
Tranche C Commitment,  and "Commitments"  means any or all of the foregoing,  as
the context may require.

         "Commitment Schedule" means the Commitment Schedule attached hereto.

         "Communications  Asset"  means  a  terrestrial  or  satellite  antenna,
licensed site, base station,  communications ground segment,  network operations
center or other telecommunications facility (other than a satellite).

         "Consolidated   Capital   Expenditures"  means,  for  any  period,  the
additions to property,  plant and equipment of the Borrower and its Consolidated
Subsidiaries for such period, as determined in accordance with GAAP.

         "Consolidated  Current  Assets"  means  at any  date  the  consolidated
current assets of the Borrower and its Consolidated  Subsidiaries  determined as
of such date.

         "Consolidated   Current   Liabilities"   means  at  any  date  (i)  the
consolidated   current   liabilities  of  the  Borrower  and  its   Consolidated
Subsidiaries  plus  (ii) the  Contingent  Obligations  of the  Borrower  and its
Consolidated  Subsidiaries with respect to the current liabilities of any Person
(other than the Borrower and its Consolidated  Subsidiaries),  all determined as
of such date.

         "Consolidated  Net Working  Investment"  means at any date Consolidated
Current  Assets  (exclusive  of cash and cash  equivalents)  minus  Consolidated
Current Liabilities (exclusive of Indebtedness).

         "Consolidated  Subsidiary"  means at any date and with  respect  to any
Person,  any  Subsidiary  or  other  entity  the  accounts  of  which  would  be
consolidated with those of such Person in its consolidated  financial statements
if such statements were prepared as of such date.




                                        5





         "Contingent  Obligation" means, as applied to any Person, any direct or
indirect  liability  of that Person  with  respect to any  Indebtedness,  lease,
dividend,  letter of credit or other  obligation (the "primary  obligations") of
another  Person (the "primary  obligor"),  including,  without  limitation,  any
obligation  of  that  Person,  whether  or  not  contingent,  (a)  to  purchase,
repurchase  or  otherwise  acquire  such  primary  obligations  or any  property
constituting direct or indirect security therefor,  or (b) to advance or provide
funds (i) for the payment or discharge of any such primary  obligation,  or (ii)
to  maintain  working  capital  or equity  capital  of the  primary  obligor  or
otherwise to maintain the net worth or solvency or any balance sheet item, level
of income or  financial  condition  of the primary  obligor,  or (c) to purchase
property, securities or services primarily for the purpose of assuring the owner
of any such  primary  obligation  of the ability of the primary  obligor to make
payment of such primary obligation,  or (d) otherwise to assure or hold harmless
the holder of any such primary  obligation  against loss in respect thereof,  or
(e) to purchase or otherwise acquire,  or otherwise to assure a creditor against
loss in respect of any Indebtedness. For purposes of this definition, the amount
of any  Contingent  Obligation  shall be  deemed  to be an  amount  equal to the
maximum reasonably anticipated liability in respect thereof.

         "Contractual  Obligation" means, as to any Person, any provision of any
security  issued by such  Person  or of any  agreement,  undertaking,  contract,
indenture, mortgage, deed of trust or other instrument, document or agreement to
which such Person is a party or by which it or any of its property is bound.

         "Controlled  Group" means the Borrower and all Persons  (whether or not
incorporated)  under  common  control or treated as a single  employer  with the
Borrower or any of its Subsidiaries  pursuant to Section 414(b), (c), (m) or (o)
of the Code.

         "Default"  means any condition or event which  constitutes  an Event of
Default  or which  with the  giving of  notice  or lapse of time or both  would,
unless cured or waived, become an Event of Default.

         "Disclosure  Schedule"  means  the  Disclosure  Schedule  of even  date
herewith attached hereto and hereby made part of this Agreement.

         "Documentation  Agent" means Morgan  Guaranty Trust Company of New York
in its  capacity  as  documentation  agent  for  the  Banks  hereunder,  and its
successors in such capacity.

         "dollars" means United States dollars.




                                        6





         "Domestic  Business  Day"  means any day except a  Saturday,  Sunday or
other day on which  commercial  banks in New York City are  authorized by law to
close.

         "Domestic Lending Office" means, as to each Bank, its office located at
its address set forth in its Administrative  Questionnaire (or identified in its
Administrative  Questionnaire  as its  Domestic  Lending  Office)  or such other
office as such Bank may hereafter  designate as its Domestic  Lending  Office by
notice to the Borrower and the Administrative Agent.

         "Effective  Date" means the date this  Agreement  becomes  effective in
accordance with Section 9.09.

         "Environmental  Claim"  means  all  claims,  however  asserted,  by any
Governmental   Authority  or  other  Person  alleging  potential   liability  or
responsibility  for  violation  of any  Environmental  Law or for  injury to the
environment or threat to public health,  personal  injury  (including  sickness,
disease or death),  property  damage,  natural  resources  damage,  or otherwise
alleging  liability  or  responsibility  for damages  (punitive  or  otherwise),
cleanup,  removal,  remedial or response costs,  restitution,  civil or criminal
penalties,  injunctive relief, or other type of relief,  resulting from or based
upon (a) the  presence,  placement,  discharge,  emission or release  (including
intentional  and   unintentional,   negligent  and   non-negligent,   sudden  or
non-sudden,  accidental or non-accidental placements, spills, leaks, discharges,
emissions  or  releases)  of any  Hazardous  Material  at, in or from  property,
whether or not owned by the Borrower, or (b) any other circumstances forming the
basis of any violation, or alleged violation, of any Environmental Law.

         "Environmental  Laws" means all applicable  federal,  state,  local and
foreign  laws,  statutes,   common  law  duties,   judicial  decisions,   rules,
regulations,  ordinances, judgements and codes, together with all administrative
orders, requests, licenses,  authorizations and permits of, and agreements with,
any Governmental Authorities,  in each case relating to the environment,  health
and  safety  or to  emissions,  discharges  or  releases,  or  the  manufacture,
distribution,  use,  treatment,  storage,  disposal,  transport or handling,  of
pollutants, contaminants, wastes or toxic or hazardous substances; including, as
they may be amended from time to time, the Comprehensive Environmental Response,
Compensation  and  Liability  Act of 1980  ("CERCLA"),  the Clean  Air Act,  the
Federal Water  Pollution  Control Act of 1972, the Solid Waste Disposal Act, the
Federal Resource Conservation and Recovery Act, the Toxic Substances Control Act
and the Emergency Planning and the Community Right-to-Know Act of 1986.




                                        7





         "ERISA" means the Employee  Retirement  Income Security Act of 1974, as
amended, or any successor statute.

         "ERISA Event" means (a) a Reportable  Event with respect to a Qualified
Plan or a  Multiemployer  Plan; (b) a withdrawal by any member of the Controlled
Group from a Qualified  Plan subject to Section 4063 of ERISA during a plan year
in which it was a  substantial  employer  (as defined in Section  4001(a)(2)  of
ERISA);  (c) a complete or partial  withdrawal  by any member of the  Controlled
Group  from a  Multiemployer  Plan;  (d) the  filing  of a notice  of  intent to
terminate, the treatment of a plan amendment as a termination under Section 4041
or 4041A of ERISA or the  commencement of proceedings by the PBGC to terminate a
Qualified Plan or Multiemployer Plan subject to Title IV of ERISA; (e) a failure
to make required contributions to a Qualified Plan or Multiemployer Plan; (f) an
event or condition  which might  reasonably  be expected to  constitute  grounds
under  Section 4042 of ERISA for the  termination  of, or the  appointment  of a
trustee  to  administer,  any  Qualified  Plan or  Multiemployer  Plan;  (g) the
imposition  of any liability  under Title IV of ERISA,  other than PBGC premiums
due but not  delinquent  under  Section  4007 of ERISA,  upon any  member of the
Controlled  Group;  (h) an application  for a funding waiver or any extension of
any amortization  period pursuant to Section 412 of the Code with respect to any
Qualified  Plan;  or (i)  any  member  of the  Controlled  Group  engages  in or
otherwise becomes liable for a non-exempt prohibited transaction.

         "Escrow  Letter" means the letter  agreement  dated March 31, 1998 from
the Borrower to the Banks and the Agents.

         "Euro-Dollar  Business  Day" means any  Domestic  Business Day on which
commercial  banks are open for  international  business  (including  dealings in
dollar deposits) in London.

         "Euro-Dollar Lending Office" means, as to each Bank, its office, branch
or   affiliate   located  at  its  address  set  forth  in  its   Administrative
Questionnaire  (or  identified  in  its  Administrative   Questionnaire  as  its
Euro-Dollar  Lending  Office) or such other office,  branch or affiliate of such
Bank as it may hereafter  designate as its Euro-Dollar  Lending Office by notice
to the Borrower and the Administrative Agent.

         "Euro-Dollar  Loan"  means  (i)  a  Loan  which  bears  interest  at  a
Euro-Dollar  Rate  pursuant to the  applicable  Notice of Borrowing or Notice of
Interest  Rate Election or (ii) an overdue  amount which was a Euro-Dollar  Loan
immediately before it became overdue.




                                        8





         "Euro-Dollar  Margin"  means a rate per annum  determined in accordance
with the Pricing Schedule.

         "Euro-Dollar  Rate"  means a rate of  interest  determined  pursuant to
Section 2.05(b) on the basis of an Adjusted London Interbank Offered Rate.

         "Euro-Dollar Reserve Percentage" has the meaning set forth in Section
2.05(b).

         "Event of Default" has the meaning set forth in Section 6.01.

         "Excess Cash Flow" means, for any fiscal year of the Borrower,  (i) the
net income of the Borrower  and its  Consolidated  Subsidiaries  for such fiscal
year,  determined on a consolidated basis for such fiscal year, plus (ii) to the
extent  deducted  in  determining  such net  income,  the  aggregate  amount  of
depreciation and amortization and other similar non-cash charges for such fiscal
year,  plus (iii) to the extent  deducted in  determining  such net income,  the
aggregate  amount of income  tax  expense  (other  than cash  taxes  paid by the
Borrower and its Consolidated Subsidiaries during such fiscal year) plus (minus)
(iv) the amount, if any, of any decrease  (increase) in Consolidated Net Working
Investment between the beginning and the end of such year minus (v) Consolidated
Capital  Expenditures  for such fiscal year minus (vi) the  aggregate  amount of
scheduled   principal   payments  of   Indebtedness  of  the  Borrower  and  its
Consolidated Subsidiaries paid during such fiscal year by the Borrower or any of
its  Consolidated  Subsidiaries,  determined on a  consolidated  basis and minus
(vii) the Excess Cash Flow for AMSC  Acquisition  Company  and its  Consolidated
Subsidiaries  for such fiscal year, to the extent the Reduction  Percentage  (as
defined in the Revolving Credit  Agreement)  thereof is applied to the reduction
of the Commitments under the Revolving Credit Agreement.

         "Existing  Credit  Facilities"  means the $75,000,000  Credit Agreement
dated as of June 28, 1996 among AMSC Subsidiary  Corporation,  the Borrower, the
Banks  listed   therein,   Morgan   Guaranty  Trust  Company  of  New  York,  as
Documentation  Agent,  and Toronto  Dominion  (Texas),  Inc., as  Administrative
Agent,   together  with  the  Loan  Documents  referred  to  therein,   and  the
$150,000,000  Credit  Agreement  dated as of June 28, 1996 among AMSC Subsidiary
Corporation,  the Borrower,  the Banks listed  therein,  Morgan  Guaranty  Trust
Company of New York, as Documentation Agent, and Toronto Dominion (Texas), Inc.,
as Administrative Agent, together with the Loan Documents referred to therein.

         "FCC" means the Federal Communications Commission or any successor
thereto.




                                        9





         "FCC  Licenses"  means  the  licenses   identified  in  the  Disclosure
Schedule, together with each other material FCC license obtained by the Borrower
or any Subsidiary of the Borrower.

         "Federal  Funds Rate" means,  for any day, the rate per annum  (rounded
upward,  if  necessary,  to the  nearest  1/100th  of 1%) equal to the  weighted
average of the rates on overnight Federal funds transactions with members of the
Federal  Reserve  System  arranged  by Federal  funds  brokers  on such day,  as
published by the Federal  Reserve Bank of New York on the Domestic  Business Day
next  succeeding  such  day,  provided  that (i) if such  day is not a  Domestic
Business  Day,  the  Federal  Funds Rate for such day shall be such rate on such
transactions on the next preceding  Domestic Business Day as so published on the
next succeeding  Domestic Business Day, and (ii) if no such rate is so published
on such next succeeding  Domestic  Business Day, the Federal Funds Rate for such
day shall be the average rate quoted to The Toronto-Dominion Bank on such day on
such transactions as determined by the Administrative Agent.

         "GAAP" means generally accepted accounting  principles set forth in the
opinions and pronouncements of the Accounting  Principles Board and the American
Institute of Certified Public  Accountants and statements and  pronouncements of
the Financial  Accounting Standards Board (or agencies with similar functions of
comparable stature and authority within the accounting  profession),  or in such
other  statements  by such other entity as may be in general use by  significant
segments  of  the  U.S.  accounting  profession,  which  are  applicable  to the
circumstances as of the date of determination.

         "Government Approvals" means any authorizations,  consents,  approvals,
licenses (including FCC licenses),  leases,  rulings,  permits,  tariffs, rates,
certifications, exemptions, filings or registrations by or with any Governmental
Authority required to be obtained or held by the Borrower.

         "Governmental  Authority" means any nation or government,  any state or
other political  subdivision  thereof,  any central bank (or similar monetary or
regulatory  authority) thereof,  any entity exercising  executive,  legislative,
judicial, regulatory or administrative functions of or pertaining to government,
and any  corporation  or other  entity  owned or  controlled,  through  stock or
capital ownership or otherwise, by any of the foregoing.

         "Group of Loans" means at any time a group of Loans  consisting  of (i)
all Loans which are Base Rate Loans at such time or (ii) all  Euro-Dollar  Loans
having the same Interest  Period at such time,  provided  that, if a Loan of any
particular Bank is




                                       10





converted to or made as a Base Rate Loan  pursuant to Article 8, such Loan shall
be  included  in the same Group or Groups of Loans from time to time as it would
have been in if it had not been so converted or made.

         "Guaranty  Issuance  Agreement" means the Guaranty  Issuance  Agreement
dated  as of  March  31,  1998,  among  Hughes,  SingTel,  Baron  Capital,  AMSC
Acquisition Company and the Borrower.

         "Guaranty  Issuance  Agreement  Event of  Default"  has the meaning set
forth in the Guaranty Issuance Agreement.

         "Hazardous  Materials"  means all those  substances which are regulated
by, or which may form the  basis of  liability  under,  any  Environmental  Law,
including all substances  identified under any Environmental Law as a pollutant,
contaminant,  waste, solid waste,  hazardous  material,  hazardous  substance or
toxic  substance,  including  petroleum or any  petroleum  derived  substance or
byproduct.

         "Hughes" means Hughes Electronics Corporation, a Delaware corporation.

         "Hughes Bridge Loan Agreement" means the Bridge Loan Agreement dated as
of December 30, 1997 by and among AMSC Subsidiary Corporation,  the Borrower and
Hughes Communications Satellite Services, Inc.

         "Hughes Guaranty" means the Guaranty,  dated as of March 31, 1998, made
by Hughes to the Administrative Agent for its own benefit and the benefit of the
Banks, as the same may be amended from time to time.

         "Indebtedness"  of  any  Person  means  without  duplication,  (a)  all
indebtedness  for borrowed  money;  (b) all  obligations  issued,  undertaken or
assumed as the deferred purchase price of capital assets;  (c) all reimbursement
obligations  with  respect  to  surety  bonds,   letters  of  credit,   bankers'
acceptances  and similar  instruments  (in each case,  whether or not  matured),
excluding  performance bonds,  letters of credit and similar undertakings in the
ordinary  course  of  business  of  the  Borrower,   to  the  extent  that  such
undertakings  do not secure an  obligation  for  borrowed  money or the deferred
purchase  price of a capital  asset;  (d) all  obligations  evidenced  by notes,
bonds,  debentures or similar  instruments,  including  obligations so evidenced
incurred in connection with the  acquisition of property,  assets or businesses,
excluding  performance bonds,  letters of credit and similar undertakings in the
ordinary  course  of  business  of  the  Borrower,   to  the  extent  that  such
undertakings  do not secure an  obligation  for  borrowed  money or the deferred
purchase price of a capital asset; (e) all indebtedness created or arising under
any  conditional  sale or  other  title  retention  agreement,  or  incurred  as





                                       11




financing,  in either case with respect to property acquired by the Person (even
though the rights and remedies of the seller or bank under such agreement in the
event of default are limited to repossession or sale of such property);  (f) all
Capital  Lease  Obligations;  (g)  all  net  obligations  with  respect  to Rate
Contracts; (h) sale-leaseback  financings;  (i) all Contingent Obligations;  and
(j) all Indebtedness  referred to in paragraphs (a) through (i) above secured by
any Lien upon or in property  (including  accounts and contract rights) owned by
such  Person,  even though such Person has not assumed or become  liable for the
payment  of  such  Indebtedness.  For  purposes  of  this  definition,  (i)  any
Indebtedness  of the  Borrower  to a  Subsidiary  of the  Borrower  and (ii) any
Indebtedness  of a Subsidiary of the Borrower to or from the Borrower or another
Subsidiary of the Borrower shall be excluded.

         "Indemnitee" has the meaning set forth in Section 9.03(b).

         "Interest  Period" means,  with respect to each  Euro-Dollar  Loan, the
period commencing on the date of borrowing specified in the applicable Notice of
Borrowing or on the date  specified in the  applicable  Notice of Interest  Rate
Election and ending one, two,  three or six months  thereafter,  as the Borrower
may elect in the applicable notice; provided that:

          (a) any Interest  Period which would  otherwise  end on a day which is
not a  Euro-Dollar  Business  Day  shall  be  extended  to the  next  succeeding
Euro-Dollar  Business Day unless such Euro-Dollar  Business Day falls in another
calendar  month,  in which  case  such  Interest  Period  shall  end on the next
preceding Euro-Dollar Business Day;

          (b) any Interest Period which begins on the last Euro-Dollar  Business
Day  of a  calendar  month  (or  on a day  for  which  there  is no  numerically
corresponding  day in the  calendar  month at the end of such  Interest  Period)
shall,  subject to clause (c) below, end on the last Euro-Dollar Business Day of
a calendar month; and

          (c) any Interest  Period which would  otherwise end after the Maturity
Date shall end on the Maturity Date.

         "Investment"  means any  investment in any Person,  whether by means of
share purchase, capital contribution,  loan, Contingent Obligation, time deposit
or otherwise (but not including any demand deposit).

         "Joint Venture" means any corporation,  association, partnership, joint
venture or other business entity of which more than 10% but of which 50% or less





                                       12





of the voting stock or other equity interests is owned or controlled directly or
indirectly by the Borrower or any of its Subsidiaries.

         "Lien"  means  any  mortgage,  deed of  trust,  pledge,  hypothecation,
assignment,  charge or deposit  arrangement,  encumbrance,  lien  (statutory  or
other) or  preference,  priority  or other  security  interest  or  preferential
arrangement of any kind or nature  whatsoever  (including,  without  limitation,
those created by,  arising under or evidenced by any  conditional  sale or other
title  retention  agreement,  the  interest  of a lessor  under a Capital  Lease
Obligation, any financing lease having substantially the same economic effect as
any of the foregoing,  or the filing of any financing statement naming the owner
of the  asset to  which  such  lien  relates  as  debtor,  under  the UCC or any
comparable  law) and any  contingent  or other  agreement  to provide any of the
foregoing.

         "Loan" means any Tranche A Loan,  Tranche B Loan or Tranche C Loan, and
"Loans" means any or all of the foregoing, as the context may require.

         "Loan  Documents"  means  this  Agreement,   the  Security  and  Pledge
Agreement,  the Shareholder Guaranties,  the Baron Capital Letter of Credit, all
Rate  Contracts  between the Borrower  and any of the Banks and all  agreements,
instruments  and documents  executed and  delivered in  connection  herewith and
therewith, each as amended, supplemented, waived or otherwise modified from time
to time.

         "London Interbank Offered Rate" has the meaning set forth in Section
2.05(b).

         "Major Casualty Event" means any loss of or damage to property  through
one or more  related  events for which the  Borrower or any of its  Subsidiaries
receives  any  insurance  proceeds  under any casualty  insurance  policy or any
condemnation  of property (or any transfer or disposition of property in lieu of
condemnation)  for which the  Borrower  or any of its  Subsidiaries  receives  a
condemnation  award or other  compensation,  with respect to which the aggregate
amount of such proceeds, award or other compensation exceeds $1,000,000.

         "Major  Contractual  Obligations" means the obligations of the Borrower
or any Subsidiary  thereof under the ACTEL Lease  Agreement and the TMI Purchase
Agreement.

         "Material  Adverse  Effect"  means a material  adverse  change in, or a
material adverse effect upon, any of (a) the operations,  business,  properties,
condition  (financial or otherwise) of the Borrower Group taken as a whole;  (b)
the ability or prospective ability of the Borrower or any of its Subsidiaries to





                                       13




perform under any Loan  Document or any Major  Contractual  Obligation;  (c) the
legality, validity, binding effect or enforceability of any Loan Document or (d)
the perfection or priority of any Lien granted to the Administrative Agent under
the Security and Pledge Agreement.

         "Maturity  Date"  means  March 31,  2003 (as such date may be  extended
pursuant to Section  2.12),  or, if such day is not a Euro-Dollar  Business Day,
the next succeeding  Euro-Dollar  Business Day unless such Euro-Dollar  Business
Day falls in another  calendar  month,  in which case the Maturity Date shall be
the next preceding Euro-Dollar Business Day.

         "MSAT-1" means the satellite that is the subject of the TMI Purchase
Agreement.

         "MSAT-2" means the satellite that is the subject of the ACTEL Lease
Agreement.

         "Multiemployer  Plan" means a "multiemployer  plan" (within the meaning
of  Section  4001(a)(3)  of ERISA) to which any member of the  Controlled  Group
makes,  is making,  or is obligated to make  contributions  or has made, or been
obligated to make, contributions.

         "Net Cash  Proceeds"  means,  with respect to any Reduction  Event,  an
amount equal to the cash proceeds  (including  lease  payments)  received by the
Borrower or any of its  Subsidiaries  (excluding  the proceeds  received by AMSC
Acquisition Company and its Subsidiaries to the extent the Reduction  Percentage
(as  defined  in the  Revolving  Credit  Agreement)  thereof  is  applied to the
reduction of the Commitments (as defined in the Revolving Credit Agreement) from
or in respect of such Reduction Event, less any out-of-pocket costs and expenses
(excluding  administrative  expenses and overhead)  reasonably  incurred by such
Person in respect of such Reduction Event; provided that Net Cash Proceeds shall
exclude  any  insurance  proceeds  received  by  the  Borrower  or  any  of  its
Subsidiaries  in respect of the loss of or damage to MSAT-2 and  required  to be
paid by the  Borrower  or such  Subsidiary  to ACTEL or its  permitted  assigns;
provided, further, that Net Cash Proceeds received by the Borrower or any of its
Subsidiaries  in respect of any period under the ACTEL Lease  Agreement shall be
reduced by the amount paid by the Borrower or such Subsidiary during such period
under the TMI Purchase  Agreement and, without  duplication,  the amount paid by
the Parent Guarantor or such Subsidiary during such period for up to $50,000,000
of  insurance  for MSAT-1  required to be obtained  hereunder  or required to be
obtained by the Shareholder Guarantors.




                                       14





         "Notes" means  promissory  notes of the Borrower,  substantially in the
form of Exhibit A hereto, evidencing the obligation of the Borrower to repay the
Loans, and "Note" means any one of such promissory notes issued hereunder.

         "Notice of Borrowing" has the meaning set forth in Section 2.02(a).

         "Notice of Interest Rate Election" has the meaning set forth in Section
2.06(a).

         "Notice  of Lien"  means  any  "notice  of lien"  or  similar  document
intended to be filed or recorded with any court,  registry,  recorder's  office,
central filing office or  Governmental  Authority for the purpose of evidencing,
creating,  perfecting or preserving the priority of a Lien securing  obligations
owing to a Governmental Authority.

         "Obligations" means all Loans, and other Indebtedness, advances, debts,
liabilities,  and obligations,  owing by the Borrower to any Bank, any Agent, or
any other Person required to be indemnified under any Loan Document, of any kind
or nature,  present or future, whether or not evidenced by any note, guaranty or
other instrument,  arising under this Agreement,  under any other Loan Document,
whether  or not for the  payment  of  money,  whether  arising  by  reason of an
extension of credit,  loan,  guaranty,  indemnification  or in any other manner,
whether direct or indirect (including those acquired by assignment), absolute or
contingent,  due or to become due, now existing or hereafter arising and however
acquired.

         "Offering  Memorandum" means the Preliminary  Offering Memorandum dated
March 9, 1998  relating  to units  consisting  of Senior  Notes and  warrants to
purchase common stock of the Borrower.

         "Parent" means, with respect  to any Bank, any Person  controlling such
Bank.

         "Participant" has the meaning set forth in Section 9.06(b).

         "PBGC" means the Pension  Benefit  Guaranty  Corporation  or any entity
succeeding to any or all of its functions under ERISA.

         "Permitted Liens" has the meaning set forth in Section 5.17.

         "Person"  means an  individual,  a  corporation,  a  limited  liability
company,  a  partnership,  an  association,  a  trust  or any  other  entity  or
organization,  including a government or political  subdivision  or an agency or
instrumentality thereof.




                                       15





         "Plan"  means an employee  benefit  plan (as defined in Section 3(3) of
ERISA)  which any member of the  Controlled  Group  sponsors or  maintains or to
which  any  member  of the  Controlled  Group  makes  or is  obligated  to  make
contributions and includes any Multiemployer Plan or Qualified Plan.

         "Pricing Schedule" means the Pricing Schedule attached hereto.

         "Prime  Rate"  means the rate of  interest  publicly  announced  by The
Toronto-Dominion Bank in New York City from time to time as its Prime Rate.

         "Principal  Subsidiary"  means  at  any  time  any  Subsidiary  of  the
Borrower,  except  Subsidiaries  which at such time have been  designated by the
Borrower (by notice to the Administrative  Agent, which may be amended from time
to time) as  nonmaterial  and which,  if aggregated  and  considered as a single
subsidiary,  would  not  meet  the  definition  of  a  "significant  subsidiary"
contained as of the date hereof in Regulation S-X of the Securities and Exchange
Commission.

         "Qualified  Plan" means a pension  plan (as defined in Section  3(2) of
ERISA) intended to be  tax-qualified  under Section 401(a) of the Code and which
any member of the Controlled Group sponsors,  maintains, or to which it makes or
is obligated to make  contributions or has made contributions at any time during
the  immediately  preceding  period  covering at least five (5) plan years,  but
excluding any Multiemployer Plan.

         "Quarterly Date" means March 31, June 30, September 30 and December 31.

         "Rate Contracts" means interest rate and currency swap agreements, cap,
floor and collar agreements,  interest rate insurance, currency spot and forward
contracts and other  agreements or arrangements  designed to provide  protection
against fluctuations in interest or currency exchange rates;  provided that such
agreements or arrangements are documented under master netting agreements.

         "Reduction  Event"  means (i) any Asset Sale,  (ii) the issuance of any
equity securities by the Borrower or any of its Subsidiaries  (other than equity
securities (x) issued pursuant to any stock option, stock purchase or other plan
intended to benefit or compensate  the  officers,  directors or employees of the
Borrower or any Principal  Subsidiary,  but only to the extent that the Net Cash
Proceeds thereof in any fiscal year of the Borrower do not exceed the sum of (A)
$2,000,000  plus (B) the  aggregate  amount by which such Net Cash Proceeds were
less than  $2,000,000  in each prior fiscal year of the Borrower  after the date





                                       16




hereof,  (y) issued to the Borrower or any of its  Subsidiaries or (z) issued by
AMRC  Holdings or any of its  Subsidiaries)  or (iii) the  occurrence of a Major
Casualty  Event.  The description of any transaction as falling within the above
definition does not affect any limitation on such transaction imposed by Article
5 of this Agreement.

         "Reduction  Percentage"  means (i) in respect  of an Asset Sale  (other
than the Satellite Lease  Arrangements) or a Major Casualty Event, 100%, (ii) in
respect of the Satellite Lease  Arrangements,  100% for the first $25,000,000 of
Net Cash Proceeds with respect  thereto and 75% for any such additional Net Cash
Proceeds,  (iii) in respect of Excess Cash Flow,  100% or (iv) in respect of the
issuance of equity  securities (other than (x) to a member of the Borrower Group
or (y) to a Shareholder  Guarantor as part of a private placement to one or more
Shareholder Guarantors) by the Borrower or any Subsidiary thereof, 50%.

         "Reference Banks" means the principal London offices of Morgan Guaranty
Trust Company of New York, The Toronto-Dominion Bank and any other Bank which is
appointed a Reference Bank by the Agents after  consultation  with the Borrower,
and "Reference Bank" means any one of such Reference Banks.

         "Regulation  U" means  Regulation  U of the Board of  Governors  of the
Federal Reserve System, as in effect from time to time.

         "Reportable Event" means any of the events set forth in Section 4043 of
ERISA or the  regulations  thereunder,  a  withdrawal  from a Plan  described in
Section 4063 of ERISA, or a cessation of operations described in Section 4062(e)
of ERISA.

         "Required  Banks"  means at any time Banks  having more than 50% of the
aggregate  amount of the  Commitments  or, if the  Commitments  shall  have been
terminated,  holding  Notes  evidencing  more than 50% of the  aggregate  unpaid
principal amount of the Loans.

         "Requirement  of Law" means,  as to any Person,  any law  (statutory or
common),  treaty,  rule or regulation or  determination of an arbitrator or of a
Governmental Authority, in each case applicable to or binding upon the Person or
any of its property or to which the Person or any of its property is subject; in
any case,  non-compliance  with which by the Borrower or any of its Subsidiaries
could reasonably be expected to have a Material Adverse Effect.

         "Responsible  Officer"  means,  with  respect to any Person,  the Chief
Executive  Officer,  the President or a duly  authorized Vice President or, with
respect to financial matters,  the Chief Financial Officer or the Treasurer,  of
such Person.




                                       17





         "Revolving Credit Agreement" means the Credit Agreement dated as of the
date hereof among the Borrower,  AMSC  Acquisition  Company,  the Agents and the
other banks party thereto, as the same may be amended, supplemented, restated or
otherwise modified from time to time.

         "Sales Corporation" means American Mobile Satellite  Sales Corporation,
a Delaware corporation.

         "Satellite  Lease  Arrangements"  means  the sale or  lease  of  MSAT-2
pursuant to the ACTEL Lease  Agreement or a  replacement  agreement  (an "MSAT-2
Lease  Agreement")  provided  that any such  replacement  agreement  shall be on
commercially  reasonable terms, and provided that (A) the consideration received
by AMSC Acquisition in respect of such sale or lease (x) consists solely of cash
and (y)  constitutes  fair market value (as determined by the Board of Directors
of  AMSC  Acquisition  set  forth  in a  resolution  thereof  delivered  to  the
Administrative  Agent,  which  determination  shall be based  upon an opinion or
appraisal  issued  by an  appraisal  or  investment  banking  firm  of  national
standing);  (B) AMSC Acquisition shall have acquired (through purchase or lease)
capacity on MSAT-1 or a reasonable substitute thereof either (x) pursuant to the
TMI Purchase  Agreement or (y) any other agreement with a term not less than the
maximum  term of the MSAT-2  Lease  Agreement  then in effect and  otherwise  on
commercially reasonable terms if (in the case of this clause (y)) in the opinion
of a nationally recognized independent expert (a) the capacity acquired pursuant
to such  replacement  agreement  is  sufficient  to permit AMSC  Acquisition  to
conduct its operations as conducted and as contemplated to be conducted  through
the  term of the  MSAT-2  Lease  Agreement  then  in  effect  and (b) the  total
consideration  paid by AMSC Acquisition for such replacement  satellite capacity
is no greater than the fair market value thereof.

         "Secured Parties" means the Agents and the Banks.

         "Security and Pledge Agreement" means the Security and Pledge Agreement
dated as of March 31, 1998 between the Borrower and the Administrative Agent.

         "Senior  Notes" means AMSC  Acquisition  Company's 12 1/4% Senior Notes
due 2008.

         "Shareholder  Guarantor  Security  Agreement"  means the  Reimbursement
Security  and Pledge  Agreement  dated as of March 31, 1998 between the Borrower
and Hughes.




                                       18





         "Shareholder Guarantors" means Hughes, SingTel and Baron Capital.

         "Shareholder   Guaranties"  means  the  Hughes  Guaranty,  the  SingTel
Guaranty and the Baron Capital Guaranty.

         "SingTel"  means  Singapore   Telecommunications  Ltd.,  a  corporation
organized under the laws of Singapore.

         "SingTel Guaranty" means the Guaranty, dated as of March 31, 1998, made
by SingTel to the  Administrative  Agent for its own  benefit and the benefit of
the Banks, as the same may be amended from time to time.

         "Subsidiary"  means, as to any Person,  any corporation or other entity
of which securities or other ownership interests having ordinary voting power to
elect a majority of the board of directors or other persons  performing  similar
functions are at the time directly or indirectly owned by such Person.

         "TMI Purchase  Agreement" means the Satellite  Purchase Agreement dated
as  of  December  4,  1997  between  TMI  Communications  and  Company,  Limited
Partnership and the Borrower.

         "Tranche A  Commitment"  means (i) with  respect to each Bank listed on
the  Commitment  Schedule,  the  amount  set forth  opposite  its name under the
heading "Tranche A Commitments" in the Commitment Schedule and (ii) with respect
to any  Assignee,  the  amount of the  transferor  Bank's  Tranche A  Commitment
assigned to such Assignee pursuant to Section 10.06, in each case as such amount
may be changed as a result of an assignment pursuant to Section 10.06.

         "Tranche B  Commitment"  means (i) with  respect to each Bank listed on
the  Commitment  Schedule,  the  amount  set forth  opposite  its name under the
heading "Tranche B Commitments" in the Commitment Schedule and (ii) with respect
to any  Assignee,  the  amount of the  transferor  Bank's  Tranche B  Commitment
assigned to such Assignee pursuant to Section 10.06, in each case as such amount
may be changed as a result of an assignment pursuant to Section 10.06.

         "Tranche C  Commitment"  means (i) with  respect to each Bank listed on
the  Commitment  Schedule,  the  amount  set forth  opposite  its name under the
heading "Tranche C Commitments" in the Commitment Schedule and (ii) with respect
to any  Assignee,  the  amount of the  transferor  Bank's  Tranche C  Commitment
assigned to such Assignee pursuant to Section 10.06, in each case as such amount
may be changed as a result of an assignment pursuant to Section 10.06.




                                       19





         "Tranche A Loan" means a loan made by a Bank  pursuant to Section  2.01
as a Tranche A Loan.

         "Tranche B Loan" means a loan made by a Bank  pursuant to Section  2.01
as a Tranche B Loan.

         "Tranche C Loan" means a loan made by a Bank  pursuant to Section  2.01
as a Tranche C Loan.

         "Type",  when used in  reference  to any Loan or  Borrowing,  refers to
whether  the rate of  interest on such Loan,  or on the Loans  compromising  the
Borrowing, is determined by reference to the Euro-Dollar Rate or the Base Rate.

         "UCC"  means  the   Uniform   Commercial  Code  as  in  effect  in  any
jurisdiction.

         "Unfunded  Pension  Liabilities"  means the excess of a Plan's  accrued
benefits,  as defined in Section 3(23) of ERISA,  over the current value of that
Plan's assets, as defined in Section 3(26) of ERISA.

         "United  States"  means the United  States of  America,  including  the
States  and  the  District  of  Columbia,  but  excluding  its  territories  and
possessions.

         "Vendor Financing Indebtedness" means Indebtedness incurred by a member
of the Parent  Guarantor  Group the  proceeds  of which are  utilized  solely to
acquire ground-based Communications Assets.

         "Withdrawal  Liabilities"  means,  as of any  determination  date,  the
aggregate amount of the liabilities,  if any,  pursuant to Section 4201 of ERISA
if the Controlled Group made a complete  withdrawal from all Multiemployer Plans
and any increase in contributions pursuant to Section 4243 of ERISA.

         SECTION 1.02.  Accounting  Terms and  Determinations.  Unless otherwise
specified  herein,  all accounting  terms used herein shall be interpreted,  all
accounting  determinations hereunder shall be made, and all financial statements
required to be delivered  hereunder shall be prepared in accordance with GAAP as
in effect from time to time,  applied on a basis consistent  (except for changes
concurred in by the Borrower's  independent  public  accountants)  with the most
recent audited consolidated or combined financial statements of the Borrower and
its  Consolidated  Subsidiaries,  delivered to the Banks;  provided that, if the
Borrower  notifies  the  Administrative  Agent  that  it  wishes  to  amend  the
definition of "Excess Cash Flow" in Section 1.01 or any covenant in Article 5 to





                                       20




eliminate the effect of any change in GAAP on the operation of such covenant (or
if the  Administrative  Agent notifies the Borrower that the Required Banks wish
to amend  Section  1.01 or  Article  5 for such  purpose),  then the  Borrower's
compliance with such covenant shall be determined on the basis of GAAP in effect
immediately  before the relevant change in GAAP became  effective,  until either
such notice is withdrawn or such covenant is amended in a manner satisfactory to
the Borrower and the Required Banks.



                                    ARTICLE 2
                                   THE CREDITS

         SECTION 2.01.  Commitments to Lend. Each Bank severally  agrees, on the
terms and conditions set forth in this Agreement, to lend to the Borrower on the
Closing  Date an  amount  not to  exceed  the  amount  of its  Commitments.  The
Borrowing  under  this  Section  shall be in an  aggregate  principal  amount of
$5,000,000 or any larger multiple of $1,000,000,  shall be made from the several
Banks ratably in proportion to their respective Commitments and shall be made by
each Bank as  Tranche A Loans,  Tranche B Loans and  Tranche C Loans  ratably in
proportion  to its  Tranche A  Commitment,  Tranche B  Commitment  and Tranche C
Commitment.  The Commitments are not revolving in nature,  and amounts repaid or
prepaid may not be reborrowed.

         SECTION  2.02.  Method of  Borrowing.  (a) The Borrower  shall give the
Administrative  Agent irrevocable  telephonic notice,  confirmed  immediately in
writing  (a  "Notice of  Borrowing"),  not later than 10:30 A.M.  (New York City
time) on (x) the  Domestic  Business Day before the  Borrowing,  if it is a Base
Rate Borrowing, and (y) the third Euro-Dollar Business Day before the Borrowing,
if it is a Euro-Dollar Borrowing, specifying:

          (i) the date of the Borrowing,  which shall be a Domestic Business Day
          in the case of a Base Rate Borrowing or a Euro-Dollar  Business Day in
          the case of a Euro-Dollar Borrowing;

          (ii) the aggregate amount of the Borrowing;

          (iii) whether the Loans  comprising the Borrowing are to bear interest
          initially at the Base Rate or a Euro-Dollar Rate; and

          (iv) in the  case of a  Euro-Dollar  Borrowing,  the  duration  of the
          Interest Period applicable  thereto,  subject to the provisions of the
          definition of Interest Period.




                                       21






          (b) Upon receipt of the Notice of Borrowing,  the Administrative Agent
shall promptly notify each Bank of the contents thereof,  of such Bank's ratable
share of the  Borrowing  and of the  portion  thereof  which  shall be made as a
Tranche A Loan, a Tranche B Loan and a Tranche C Loan.

          (c) Not later  than 12:00 Noon (New York City time) on the date of the
Borrowing, each Bank shall make available its ratable share of the Borrowing, in
Federal  or  other  funds  immediately  available  in  New  York  City,  to  the
Administrative  Agent at its  address  referred to in Section  5.03.  Unless the
Administrative  Agent  determines  that any  applicable  condition  specified in
Article 3 has not been satisfied,  the Administrative  Agent will make the funds
so received  from the Banks  available  to the  Borrower  at the  Administrative
Agent's aforesaid address.

          (d) Unless the Administrative  Agent shall have received notice from a
Bank prior to the date of the Borrowing  that such Bank will not make  available
to  the   Administrative   Agent  such  Bank's  share  of  the  Borrowing,   the
Administrative  Agent may assume that such Bank has made such share available to
the  Administrative  Agent  on the  date of the  Borrowing  in  accordance  with
subsection  (c) of this  Section and the  Administrative  Agent may, in reliance
upon  such   assumption,   make  available  to  the  Borrower  on  such  date  a
corresponding amount. If and to the extent that such Bank shall not have so made
such share  available to the  Administrative  Agent,  such Bank and the Borrower
severally  agree to repay to the  Administrative  Agent forthwith on demand such
corresponding  amount together with interest thereon, for each day from the date
such  amount is made  available  to the  Borrower  until the date such amount is
repaid to the Administrative  Agent, at (i) in the case of the Borrower,  a rate
per annum equal to the higher of the Federal  Funds Rate and the  interest  rate
applicable  thereto  pursuant to Section 2.05 and (ii) in the case of such Bank,
the Federal  Funds Rate.  If such Bank shall repay to the  Administrative  Agent
such  corresponding  amount,  such amount so repaid shall constitute such Bank's
Loan included in the Borrowing for purposes of this Agreement.

         SECTION  2.03.  Notes.  (a) The  Tranche  A Loans,  Tranche B Loans and
Tranche C Loans of each Bank shall each be evidenced by a single Note payable to
the order of such Bank for the account of its  Applicable  Lending  Office in an
amount equal to the aggregate  unpaid  principal amount of such Bank's Tranche A
Loans,  Tranche B Loans and Tranche C Loans,  as the case may be. Each reference
in this  Agreement  to the  "Notes"  of a Bank  shall be  deemed to refer to and
include any or all of the Notes of such Bank  described in this Section,  as the
context may require.




                                       22





          (b) Each Bank may, by notice to the  Borrower  and the  Administrative
Agent,  request that its Tranche A Loans, Tranche B Loans and Tranche C Loans of
a  particular  Type be  evidenced  by a separate  Note in an amount equal to the
aggregate  unpaid  principal  amount of such  Loans.  Each such Note shall be in
substantially  the form of Exhibit A hereto with  appropriate  modifications  to
reflect the fact that it evidences solely Loans of the relevant Type.

          (c) Upon receipt of each Bank's Notes pursuant to Section 3.01(a), the
Documentation  Agent  shall  forward  such Notes to such  Bank.  Each Bank shall
record the date, amount and Type of each Loan made by it and the date and amount
of each payment of principal  made by the Borrower  with respect  thereto on the
appropriate  Note,  and may,  if such  Bank so  elects  in  connection  with any
transfer or enforcement of any of its Notes,  endorse on the schedule  forming a
part thereof  appropriate  notations to evidence the foregoing  information with
respect to each Loan then outstanding  thereunder;  provided that the failure of
any Bank to make any such  recordation  or  endorsement  shall  not  affect  the
obligations  of the Borrower  hereunder or under the Notes.  Each Bank is hereby
irrevocably  authorized by the Borrower so to endorse its Notes and to attach to
and make a part of its Notes a  continuation  of any such  schedule  as and when
required.

          SECTION 2.04. Maturity of Loans; Mandatory Prepayments.  (a) Any Loans
outstanding on the Maturity Date (together with accrued interest  thereon) shall
be due and payable on such date.

         (b)    In addition the Loans shall be prepaid in the following amounts:

          (i) in the event that the Borrower or any of its Subsidiaries shall at
          any time, or from time to time,  receive after the date hereof any Net
          Cash Proceeds of any Reduction Event, an amount equal to the Reduction
          Percentage  of such Net Cash  Proceeds  on the date of receipt of such
          Net Cash Proceeds; and

          (ii) on each date on which the  Borrower  is  required  to notify  the
          Administrative  Agent of the  Excess  Cash  Flow for any  fiscal  year
          pursuant  to  Section  5.02(b),  an  amount  equal  to  the  Reduction
          Percentage of Excess Cash Flow for such fiscal year.

         (c) Each  prepayment of Loans pursuant to subsection (b) above shall be
applied ratably to the respective Tranche A Loans, Tranche B Loans and Tranche C
Loans of the Banks.




                                       23





         SECTION  2.05.  Interest  Rates.  (a) Each Base Rate  Loan  shall  bear
interest on the outstanding principal amount thereof, for each day from the date
such Loan is made until it becomes  due,  at a rate per annum  equal to the Base
Rate for such day. Such interest  shall be payable  quarterly in arrears on each
Quarterly  Date and, with respect to the principal  amount of any Base Rate Loan
converted to a Euro-Dollar  Loan, on each date a Base Rate Loan is so converted.
Any overdue  principal of or interest on any Base Rate Loan shall bear interest,
payable on demand,  for each day until paid at a rate per annum equal to the sum
of 2% plus the rate otherwise applicable to Base Rate Loans for such day.

          (b) Each  Euro-Dollar  Loan shall  bear  interest  on the  outstanding
principal  amount thereof,  for each day during each Interest Period  applicable
thereto, at a rate per annum equal to the sum of the Euro-Dollar Margin for such
day plus the Adjusted London Interbank  Offered Rate applicable to such Interest
Period.  Such interest shall be payable for each Interest Period on the last day
thereof and, if such Interest  Period is longer than three months,  at intervals
of three months after the first day thereof.

         The "Adjusted London Interbank Offered Rate" applicable to any Interest
Period means a rate per annum equal to the quotient obtained (rounded upward, if
necessary,  to the next higher  1/10,000 of 1%) by dividing  (i) the  applicable
London  Interbank  Offered  Rate by (ii)  1.00  minus  the  Euro-Dollar  Reserve
Percentage.

         The "London  Interbank  Offered Rate" applicable to any Interest Period
means the average (rounded upward, if necessary,  to the next higher 1/16 of 1%)
of the  respective  rates per annum at which  deposits in dollars are offered to
each of the  Reference  Banks in the London  interbank  market at  approximately
11:00 A.M.  (London time) two Euro-Dollar  Business Days before the first day of
such Interest Period in an amount approximately equal to the principal amount of
the Euro-Dollar  Loan of such Reference Bank to which such Interest Period is to
apply and for a period of time comparable to such Interest Period.

          "Euro-Dollar  Reserve  Percentage"  means for any day that  percentage
(expressed  as a decimal)  which is in effect on such day, as  prescribed by the
Board  of  Governors  of the  Federal  Reserve  System  (or any  successor)  for
determining  the maximum  reserve  requirement  for a member bank of the Federal
Reserve System in New York City with deposits  exceeding five billion dollars in
respect of  "Eurocurrency  liabilities"  (or in respect of any other category of
liabilities  which includes  deposits by reference to which the interest rate on
Euro-Dollar Loans is determined or any category of extensions of credit or other
assets which includes loans by a non-United  States office of any Bank to United





                                       24




States residents).  The Adjusted London Interbank Offered Rate shall be adjusted
automatically  on and as of the effective date of any change in the  Euro-Dollar
Reserve Percentage.

          (c) Any overdue principal of or interest on any Euro-Dollar Loan shall
bear  interest,  payable on demand,  for each day until paid at a rate per annum
equal to the  higher of (i) the sum of 2% plus the  Euro-Dollar  Margin for such
day plus the quotient obtained (rounded upward, if necessary, to the next higher
1/10,000 of 1%) by dividing (x) the average  (rounded upward,  if necessary,  to
the next higher 1/16 of 1%) of the  respective  rates per annum at which one day
(or,  if such amount due remains  unpaid  more than three  Euro-Dollar  Business
Days,  then for such  other  period of time not  longer  than six  months as the
Administrative  Agent may select) deposits in dollars in an amount approximately
equal to such overdue  payment due to each of the Reference Banks are offered to
such Reference  Bank in the London  interbank  market for the applicable  period
determined  as  provided  above  by  (y)  1.00  minus  the  Euro-Dollar  Reserve
Percentage (or, if the  circumstances  described in clause (a) or (b) of Section
8.01  shall  exist,  at a rate  per  annum  equal to the sum of 2% plus the rate
applicable  to Base  Rate  Loans  for such  day) and (ii) the sum of 2% plus the
Euro-Dollar  Margin for such day plus the Adjusted London Interbank Offered Rate
applicable to such Loan at the date such payment was due.

          (d) The  Administrative  Agent  shall  determine  each  interest  rate
applicable to the Loans hereunder.  The  Administrative  Agent shall give prompt
notice to the Borrower and the  participating  Banks of each rate of interest so
determined,  and its determination thereof shall be conclusive in the absence of
manifest error.

          (e) Each  Reference  Bank  agrees to use its best  efforts  to furnish
quotations to the Administrative  Agent as contemplated by this Section.  If any
Reference Bank does not furnish a timely  quotation,  the  Administrative  Agent
shall  determine  the relevant  interest  rate on the basis of the  quotation or
quotations  furnished by the  remaining  Reference  Bank or Banks or, if none of
such  quotations is available on a timely basis,  the provisions of Section 8.01
shall apply.

         SECTION 2.06. Method of Electing Interest Rates. (a) The Loans included
in the Borrowing shall bear interest  initially at the type of rate specified by
the Borrower in the Notice of Borrowing.  Thereafter, the Borrower may from time
to time  elect to change or  continue  the type of  interest  rate borne by each
Group of Loans  (subject  in each  case to the  provisions  of  Article  8),  as
follows:

          (i) if such  Loans  are Base Rate  Loans,  the  Borrower  may elect to
         convert such Loans to Euro-Dollar Loans as of any Euro-Dollar  Business
         Day and




                                       25






         (ii) if such Loans are  Euro-Dollar  Loans,  the  Borrower may elect to
         convert  such Loans to Base Rate Loans or elect to continue  such Loans
         as  Euro-Dollar  Loans for an additional  Interest  Period,  subject to
         Section  2.10  in the  case  of any  such  conversion  or  continuation
         effective  on any day  other  than the  last  day of the  then  current
         Interest Period applicable to such Loans.

Each  such  election  shall be made by  giving  irrevocable  telephonic  notice,
confirmed  immediately in writing (a "Notice of Interest Rate  Election") to the
Administrative Agent not later than 10:30 A.M. (New York City time) on the third
Euro-Dollar Business Day before the conversion or continuation  selected in such
notice is to be  effective.  A Notice of Interest  Rate  Election  may, if it so
specifies,  apply to only a portion  of the  aggregate  principal  amount of the
relevant  Group of Loans;  provided  that (i) such portion is allocated  ratably
among the Loans  comprising such Group and (ii) the portion to which such Notice
applies,  and the  remaining  portion  to  which  it does  not  apply,  are each
$5,000,000  or any larger  multiple of  $1,000,000.  In no event shall the total
number of Groups of Loans at any one time outstanding exceed ten, and each Group
of Loans  shall at all times  consist  of  Tranche A Loans,  Tranche B Loans and
Tranche C Loans of the Banks ratably in proportion to their respective Tranche A
Commitments, Tranche B Commitments and Tranche C Commitments.

         (b) Each Notice of Interest Rate Election shall specify:

          (i) the Group of Loans (or,  subject to the last  sentence  of Section
          2.02(a), portion thereof) to which such notice applies;

          (ii) the date on which the conversion or continuation selected in such
          notice is to be  effective,  which shall  comply  with the  applicable
          clause of subsection (a) above;

          (iii) if the Loans comprising such Group are to be converted,  the new
          Type of Loans and, if the Loans being  converted are to be Euro-Dollar
          Loans, the duration of the next succeeding  Interest Period applicable
          thereto; and

          (iv) if such Loans are to be  continued  as  Euro-Dollar  Loans for an
          additional  Interest Period, the duration of such additional  Interest
          Period.

Each  Interest  Period  specified in a Notice of Interest  Rate  Election  shall
comply with the  provisions of the  definition  of Interest  Period set forth in
Section 1.01.




                                       26





          (c) If, upon the expiration of any Interest  Period  applicable to any
Eurodollar  Loan,  the Borrower has not given a timely  Notice of Interest  Rate
Election with respect to such Loan, the Administrative  Agent shall be deemed to
have  received a Notice of Interest Rate Election from the Borrower with respect
to such Loan requesting that such Loan be converted into a Base Rate Loan on the
last day of the Interest Period applicable to such Loan.

          (d) Upon  receipt  of a Notice  of  Interest  Rate  Election  from the
Borrower  pursuant to  subsection  (a) above or a deemed  receipt of a Notice of
Interest Rate  Election  pursuant to subsection  (c) above,  the  Administrative
Agent shall  promptly  notify each Bank of the contents  thereof and such notice
shall not thereafter be revocable by the Borrower.

          (e) An  election by the  Borrower  to change or  continue  the rate of
interest  applicable  to any Group of Loans  pursuant to this Section  shall not
constitute a "Borrowing" subject to the provisions of Section 3.02.

         SECTION 2.07.  Mandatory Termination and Reduction of Commitments.
The Commitments shall terminate on the Closing Date.

         SECTION  2.08.  Optional  Prepayments.  (a)  Subject in the case of any
Euro-Dollar  Borrowing  to Section  2.12,  the Borrower  may,  upon at least one
Domestic Business Day's notice to the Administrative  Agent, prepay any Group of
Base Rate Loans, or upon at least three Euro-Dollar Business Days' notice to the
Administrative  Agent,  prepay any Group of Euro-Dollar  Loans,  in each case in
whole  at any  time,  or from  time to  time  in  part  in  amounts  aggregating
$5,000,000 or any larger multiple of $1,000,000,  by paying the principal amount
to be prepaid  together with accrued interest thereon to the date of prepayment.
Each such optional  prepayment  shall be applied to prepay ratably the Tranche A
Loans, Tranche B Loans and Tranche C Loans of the several Banks included in such
Group.

          (b) Upon receipt of a notice of  prepayment  pursuant to this Section,
the Administrative Agent shall promptly notify each Bank of the contents thereof
and of such Bank's  ratable share of such  prepayment  and such notice shall not
thereafter be revocable by the Borrower.

         SECTION 2.09. General Provisions as to Payments. (a) The Borrower shall
make each  payment  of  principal  of,  and  interest  on, the Loans and of fees
hereunder,  not later than 12:00 Noon (New York City time) on the date when due,
in  Federal  or other  funds  immediately  available  in New York  City,  to the
Administrative   Agent  at  its  address   referred  to  in  Section  5.03.  The





                                       27




Administrative  Agent will promptly distribute to each Bank its ratable share of
each such payment  received by the  Administrative  Agent for the account of the
Banks to be applied  ratably  to the  Tranche A Loans,  the  Tranche B Loans and
Tranche C Loans of the Banks.  Whenever any payment of principal of, or interest
on, the Base Rate Loans or of fees shall be due on a day which is not a Domestic
Business  Day,  the date for  payment  thereof  shall  be  extended  to the next
succeeding  Domestic  Business  Day.  Whenever any payment of  principal  of, or
interest  on,  the  Euro-Dollar  Loans  shall  be  due on a day  which  is not a
Euro-Dollar  Business Day, the date for payment thereof shall be extended to the
next succeeding  Euro-Dollar  Business Day unless such Euro-Dollar  Business Day
falls in another  calendar  month,  in which case the date for  payment  thereof
shall  be the  next  preceding  Euro-Dollar  Business  Day.  If the date for any
payment of  principal is extended by  operation  of law or  otherwise,  interest
thereon shall be payable for such extended time.

          (b) Unless the  Administrative  Agent shall have received  notice from
the  Borrower  prior  to the  date on  which  any  payment  is due to the  Banks
hereunder   that  the  Borrower  will  not  make  such  payment  in  full,   the
Administrative  Agent may assume that the Borrower has made such payment in full
to the Administrative  Agent on such date and the  Administrative  Agent may, in
reliance upon such assumption,  cause to be distributed to each Bank on such due
date an amount equal to the amount then due such Bank. If and to the extent that
the Borrower  shall not have so made such payment,  each Bank shall repay to the
Administrative  Agent  forthwith on demand such amount  distributed to such Bank
together  with  interest  thereon,  for each day from the date  such  amount  is
distributed  to such Bank  until the date such Bank  repays  such  amount to the
Administrative Agent, at the Federal Funds Rate.

         SECTION  2.10.  Funding  Losses.  If the Borrower  makes any payment of
principal  with  respect  to any  Euro-Dollar  Loan or any  Euro-Dollar  Loan is
converted (pursuant to Article 2, 6 or 8 or otherwise) on any day other than the
last  day of an  Interest  Period  applicable  thereto,  or the  last  day of an
applicable period fixed pursuant to Section 2.05(c), or if the Borrower fails to
borrow or prepay any  Euro-Dollar  Loans after notice has been given to any Bank
in accordance with Section  2.02(a),  2.04 or 2.08, the Borrower shall reimburse
each Bank within 15 days after demand for any resulting loss or expense incurred
by it (or by an  existing  or  prospective  Participant  in the  related  Loan),
including  (without  limitation) any loss incurred in obtaining,  liquidating or
employing  deposits from third  parties,  but  excluding  loss of margin for the
period  after any such  payment  or  conversion  or failure to borrow or prepay,
provided that such Bank shall have delivered to the Borrower a certificate as to
the amount of such loss or expense, which certificate shall be conclusive in the
absence of manifest error.

         SECTION 2.11.  Computation of Interest and Fees.  Interest based on the
Prime Rate and  commitment  fees  hereunder  shall be computed on the basis of a





                                       28





year of 365 days (or 366 days in a leap year) and paid for the actual  number of
days elapsed  (including  the first day but excluding  the last day).  All other
interest  shall be  computed on the basis of a year of 360 days and paid for the
actual  number of days elapsed  (including  the first day but excluding the last
day).

          SECTION 2.12.  Extension of Maturity  Date. If the Borrower  wishes to
extend the Maturity Date then in effect,  the Borrower shall give written notice
to the  Administrative  Agent not less  than 13  months  nor more than 18 months
prior to the Maturity Date then in effect,  whereupon the  Administrative  Agent
shall  promptly  notify  each  Bank of  such  notice.  Each  Bank  will  use its
reasonable efforts to respond to such request in writing,  whether affirmatively
or negatively,  as it may elect in its sole discretion,  within 30 days after it
receives such notice from the Administrative  Agent. If the Administrative Agent
receives an  affirmative  response in writing  from each Bank within such 30 day
period,  the Maturity Date then in effect shall be extended for one year (but in
no event later than March 31,  2006) and the  Administrative  Agent shall notify
the Borrower (with a copy to the  Shareholder  Guarantors,  it being  understood
that the consent of the  Shareholder  Guarantors  is not  required  for any such
extension  and any  failure  to give  any  such  notice  shall  not  affect  any
Shareholder  Guarantor's  obligations  under its  Shareholder  Guaranty) and the
Banks of such extension.



                                    ARTICLE 3
                                   CONDITIONS

          SECTION  3.01.  Closing.   The  closing  hereunder  shall  occur  upon
satisfaction of the following conditions:

          (a) the Documentation  Agent shall have received all of the following,
in form and substance  satisfactory to the Documentation Agent and in sufficient
copies for each Bank:

          (i) duly  executed  Notes for the  account  of each  Bank  dated on or
          before the Closing Date complying with the provisions of Section 2.03;

          (ii) the Security and Pledge Agreement duly executed by the Borrower;

          (iii) the  articles or  certificate  of  incorporation  of each of the
          Borrower and the Shareholder  Guarantors (other than Baron Capital) as
          in effect on the Closing Date,  certified by the Secretary of State or





                                       29




          equivalent  official  of the  jurisdiction  of  incorporation  of such
          Person as of a recent date and by the Secretary or Assistant Secretary
          of such Person as of the Closing  Date,  and the bylaws of such Person
          as in  effect on the  Closing  Date,  certified  by the  Secretary  or
          Assistant Secretary of such Person as of the Closing Date;

          (iv) a good standing  certificate  for the Borrower from the Secretary
          of State of its  state of  incorporation  and  each  state  where  the
          Borrower is qualified to do business as a foreign  corporation as of a
          recent  date,  together  with a  bring-down  certificate  by  telex or
          telecopy, dated the Closing Date;

          (v) copies of the  resolutions  of the board of  directors  of (x) the
          Borrower  approving  and  authorizing  the  execution,   delivery  and
          performance  by the  Borrower  of this  Agreement  and the other  Loan
          Documents to be delivered by it and  authorizing  the borrowing of the
          Loans,  certified  as of  the  Closing  Date  by the  Secretary  or an
          Assistant  Secretary of the Borrower,  and (y) each of the Shareholder
          Guarantors  (other than Baron Capital)  approving and  authorizing the
          execution,  delivery  and  performance  by  such  Person  of all  Loan
          Documents to be  delivered by it,  certified as of the Closing Date by
          the Secretary or an Assistant Secretary of such Person;

          (vi) a certificate of the Secretary or an Assistant  Secretary of each
          of the  Borrower  and each  Shareholder  Guarantor  (other  than Baron
          Capital)  certifying  the names and true  signatures  of its  officers
          authorized to execute,  deliver and perform,  as applicable,  all Loan
          Documents to be delivered by it hereunder;

          (vii) a certificate  signed by a Responsible  Officer of the Borrower,
          dated as of the Closing Date,  stating that each of the conditions set
          forth in Sections 3.01(b) through (e) is satisfied as of such date;

          (viii) written advice  relating to such Lien and judgment  searches as
          either  Agent  shall  have   requested  of  the  Borrower,   and  such
          termination  statements  or other  documents  as may be  necessary  to
          release any Lien in favor of any third party not  otherwise  permitted
          by Section 5.17;

          (ix) evidence (A) that all filings,  recordations,  registrations  and
          other actions necessary or, in the opinion of either Agent,  desirable
          to perfect and protect a first  priority  (except for Permitted  Liens
          arising by  operation  of law)  security  interest  in and Lien on the
          Collateral  in  favor  of the  Administrative  Agent  have  been  duly
          effected  or taken;  (B) that each Lien  created by the  Security  and





                                       30




          Pledge Agreement in the Collateral  constitutes a perfected Lien on or
          in all right,  title,  estate and  interest  of the  Borrower  in such
          Collateral  prior and superior to all Liens other than Permitted Liens
          arising  by  operation  of  law;  and  (C)  that  all   necessary  and
          appropriate consents to the creation and perfection of such Liens will
          have been obtained;

          (x) an  opinion  of (w)  Randy  S.  Segal,  counsel  to the  Borrower,
          substantially in the form of Exhibit B hereto,  (x) counsel reasonably
          satisfactory to the Agents to each Shareholder Guarantor,  in form and
          substance  satisfactory to the Documentation Agent, and (y) Davis Polk
          & Wardwell,  special counsel to the Agents,  substantially in the form
          of Exhibit C hereto;

          (xi) a copy of the financial statements of the Borrower referred to in
          Section  4.10(a) and (b),  certified by a  Responsible  Officer of the
          Borrower;

          (xii)  a  Shareholder  Guaranty  duly  executed  by  each  Shareholder
          Guarantor,  the Baron Capital  Letter of Credit and the Escrow Letter;
          and

          (xiii) all documents the  Documentation  Agent may reasonably  request
          relating  to the  existence  of the  Borrower,  any of the  Borrower's
          Subsidiaries or any Shareholder Guarantor, the corporate authority for
          and the validity of this Agreement, the Notes, the Security and Pledge
          Agreement  or  the  Shareholder  Guaranties,  and  any  other  matters
          relevant  hereto,  all  in  form  and  substance  satisfactory  to the
          Documentation Agent;

          (b) all  costs,  accrued  and  unpaid  fees and  expenses  (including,
without  limitation,  upfront  fees,  participation  fees  and  legal  fees  and
expenses) to the extent then due and payable on the Closing Date by the Borrower
hereunder shall have been paid;

          (c) AMSC  Acquisition  Company and the  Borrower  shall have  received
proceeds (net of fees and interest  reserves) of not less than $140,000,000 from
the issuance of its Senior Notes,  all conditions to the Acquisition  (including
receipt  of any  approvals  of the  FCC)  shall  have  been  satisfied  and  the
Acquisition shall have been consummated;

          (d) The Borrower  shall have  entered into a Rate  Contract to fix its
interest rate  obligations  under this  Agreement for three years and shall have
prefunded its interest obligations thereunder;

          (e) the Hughes Bridge Loan  Agreement  shall have been  terminated and
all amounts payable thereunder shall have paid in full; and





                                       31





          (f) the Existing Credit  Facilities shall have been terminated and all
amounts payable thereunder shall have been paid in full.

The Documentation  Agent shall promptly notify the Borrower and the Banks of the
Closing  Date,  and such notice shall be  conclusive  and binding on all parties
hereto.

         SECTION 3.02.  Borrowings. The obligation of any Bank to make a Loan on
the occasion of the  Borrowing is subject to the  satisfaction  of the following
conditions:

          (a) the fact that the Closing Date shall have  occurred on or prior to
March 31, 1998;

          (b) receipt by the  Administrative  Agent of a Notice of  Borrowing as
required by Section 2.02(a);

          (c) the fact that,  immediately  after the  Borrowing,  the  aggregate
outstanding  principal  amount of the Loans will not exceed the aggregate amount
of the Commitments;

          (d) the fact  that,  immediately  before and after the  Borrowing,  no
Default shall have occurred and be continuing; and

          (e) the fact that the  representations  and warranties of the Borrower
contained  in the  Loan  Documents  shall  be true on and as of the  date of the
Borrowing.

The Borrowing  hereunder shall be deemed to be a representation  and warranty by
the Borrower on the date of the  Borrowing as to the facts  specified in clauses
(b) through (e) of this Section.



                                    ARTICLE 4
                         REPRESENTATIONS AND WARRANTIES

         The Borrower  represents and warrants (in each case after giving effect
to the  Acquisition;  provided that for periods prior to the Effective Date, the
representations  and warranties with respect to ARDIS are made to the Borrower's
best  knowledge in reliance on the  representations  and warranties in the ARDIS
Purchase  Agreement)  that,  except as set forth in the  section (if any) of the
Disclosure Schedule corresponding to the Section heading below:




                                       32





         SECTION 4.01.  Corporate  Existence and Power. Each of the Borrower and
its Principal  Subsidiaries  (a) is a  corporation  duly  incorporated,  validly
existing  and in  good  standing  under  the  laws  of the  jurisdiction  of its
incorporation;  (b) has the power and  authority  and all material  governmental
licenses,  authorizations,  consents  and  approvals  required  to  carry on its
business  as now  conducted;  (c) is duly  qualified  as a foreign  corporation,
licensed  and in good  standing  under the laws of each  jurisdiction  where its
ownership,  lease or  operation  of  property  or the  conduct  of its  business
requires such  qualification;  and (d) is in compliance with all Requirements of
Law  except,  in the case of  clauses  (c) and (d),  where the  failure to be so
qualified or in compliance  could not  reasonably be expected to have a Material
Adverse Effect.

         SECTION 4.02. Corporate Authorization; No Contravention. The execution,
delivery and  performance  by each of the Borrower and its  Subsidiaries  of any
Loan Document to which it is a party have been duly  authorized by all necessary
corporate  action  and do not and will  not:  (a)  contravene  the terms of such
Person's  certificate of incorporation,  bylaws or other organization  document;
(b) conflict with or result in any breach or  contravention  of, or the creation
of any Lien under,  any indenture,  agreement,  lease,  instrument,  Contractual
Obligation,  injunction,  order, decree or undertaking to which such Person is a
party; or (c) violate any Requirement of Law.

         SECTION 4.03. Government  Approvals.  All material Government Approvals
heretofore required to be obtained have been duly obtained, were validly issued,
are in full force and effect, are not subject to appeal and are held in the name
of, or for the  benefit  of, the  appropriate  Persons.  There is no  proceeding
pending  or, to the best  knowledge  of the  Borrower,  threatened  against  the
Borrower or any of its  Subsidiaries,  or any property of the Borrower or any of
its  Subsidiaries,  which seeks,  or may  reasonably  be  expected,  to rescind,
terminate, materially adversely modify or suspend any of the FCC Licenses. There
has not occurred any event that would make  unlikely the delivery or issuance as
anticipated  of, and when and as needed all such Government  Approvals.  No such
Government  Approval already obtained is subject to any restriction,  condition,
limitation or other  provision that would have a Material  Adverse  Effect.  The
information  set forth in each  application  submitted by the Borrower or any of
its  Subsidiaries in connection  with each such Government  Approval is accurate
and complete in all material respects taken as a whole, except for statements or
omissions  which  could not  reasonably  be  expected  to affect  adversely  the
validity of such Government  Approvals.  No other material consent,  approval or
authorization of, or declaration or filing with, any other Person is required in
connection with the execution, delivery, performance, validity or enforceability
of this Agreement or any other Loan Document.




                                       33





         SECTION  4.04.  Binding  Effect.  This  Agreement  and each  other Loan
Document to which the Borrower or any of its  Subsidiaries is a party constitute
the legal,  valid and binding  obligations of such Person,  enforceable  against
such Person in accordance with their respective terms,  except as enforceability
may be limited by applicable bankruptcy,  insolvency,  or similar laws affecting
the  enforcement  of  creditors'  rights  generally or by  equitable  principles
relating to enforceability.

         SECTION  4.05.  Litigation.   Except  for  matters  arising  after  the
Effective Date which could not reasonably be expected to have a Material Adverse
Effect, there are no actions, suits, proceedings, claims or disputes pending, or
to the best  knowledge of the Borrower,  threatened or  contemplated  at law, in
equity,  in  arbitration  or before  any  Governmental  Authority,  against  the
Borrower or any of its Subsidiaries or any of their respective properties which:
(a) purport to affect or pertain to this Agreement, or any Loan Document, or any
of the  transactions  contemplated  hereby  or  thereby;  or  (b) if  determined
adversely  to the  Borrower  or any of its  Subsidiaries,  could have a Material
Adverse Effect. No injunction, writ, temporary restraining order or any order of
any  nature  has  been  issued  by any  court or  other  Governmental  Authority
purporting to enjoin or restrain the execution, delivery and performance of this
Agreement  or any  other  Loan  Document,  or  directing  that the  transactions
provided for herein or therein not be consummated as herein or therein provided.

         SECTION  4.06.  No  Default.  No Default or Event of Default  exists or
would  result from the  incurring of  Obligations  by the Borrower or any of its
Subsidiaries  under  any Loan  Document.  Neither  the  Borrower  nor any of its
Subsidiaries is in default under or with respect to any  Contractual  Obligation
in any respect which,  individually  or together with all such  defaults,  could
have a Material Adverse Effect.

         SECTION  4.07.  ERISA  Compliance.  (a) Section 4.07 of the  Disclosure
Schedule  lists all Plans  maintained  or  sponsored by the Borrower or to which
either of them is obligated  to  contribute,  and  separately  identifies  Plans
intended to be Qualified Plans and Multiemployer Plans. All written descriptions
thereof  provided to the Agents are true and complete in all material  respects.
Each  Plan  is in  compliance  in all  material  respects  with  the  applicable
provisions  of ERISA,  the Code and other  Federal or state law,  including  all
requirements  under the Code or ERISA for  filing  reports  (which  are true and
correct in all material  respects as of the date filed),  and benefits have been
paid in accordance with the provisions of the Plan. Each Qualified Plan has been
determined by the IRS to qualify under Section 401 of the Code,  and to the best
knowledge  of the Borrower  nothing has  occurred  which would cause the loss of
such qualification.




                                       34





          (b) There is no  outstanding  liability  under  Title IV of ERISA with
respect to any Plan  maintained  or  sponsored  by any member of the  Controlled
Group (as to which the  Borrower is or may be liable),  nor with  respect to any
Plan to which any member of the Controlled Group  contributes or is obligated to
contribute  (wherein the Borrower is or may be liable).  No Plan  maintained  or
sponsored by the Borrower  provides medical or other welfare benefits or extends
coverage   relating  to  such  benefits  beyond  the  date  of  a  participant's
termination of employment  with the Borrower,  except to the extent  required by
Section  4980B of the Code and at the sole  expense  of the  participant  or the
beneficiary  of the  participant to the fullest  extent  permissible  under such
Section of the Code. The Borrower has complied in all material respects with the
notice and continuation coverage requirements of Section 4980B of the Code.

          (c) No ERISA  Event has  occurred or is  reasonably  expected to occur
with respect to any Plan maintained or sponsored by the Borrower or to which the
Borrower  is  obligated  to  contribute.  There are no  pending  or, to the best
knowledge of the Borrower,  threatened claims,  actions or lawsuits,  other than
routine  claims for  benefits  in the usual and  ordinary  course,  asserted  or
instituted  against (i) any Plan  maintained or sponsored by the Borrower or its
assets,  (ii) any member of the  Controlled  Group with respect to any Qualified
Plan of the Borrower,  or (iii) any fiduciary with respect to any Plan for which
the  Borrower  may be directly or  indirectly  liable,  through  indemnification
obligations or otherwise.  The Borrower has not incurred and does not reasonably
expect to incur (i) any  liability  (and no event has occurred  which,  with the
giving of notice under  Section 4219 of ERISA,  would result in such  liability)
under  Section  4201 of ERISA with respect to a  Multiemployer  Plan or (ii) any
liability  under Title IV of ERISA (other than  premiums due and not  delinquent
under  Section  4007 of ERISA)  with  respect to a Plan.  The  Borrower  has not
transferred any Unfunded  Pension  Liability  outside of the Controlled Group or
otherwise  engaged in a  transaction  that  could be subject to Section  4069 or
4212(c) of ERISA.

          (d) The  Borrower  has  not  engaged,  directly  or  indirectly,  in a
non-exempt  prohibited  transaction  (as defined in Section  4975 of the Code or
Section 406 of ERISA) in connection with any Plan, which  transaction could have
a Material Adverse Effect.

         SECTION  4.08.  Title  to  Property.  Each  of  the  Borrower  and  its
Subsidiaries  has good  record  and  marketable  title in fee simple to or valid
leasehold  interests in all real property used in its business,  except for such
defects in title as could not, individually or in the aggregate, have a Material
Adverse  Effect.  Such real property is free and clear of all Liens or rights of
others, except Permitted Liens.




                                       35





         SECTION  4.09.  Taxes.  Each of the Borrower and its  Subsidiaries  has
filed all Federal  and other  material  tax  returns and reports  required to be
filed and have paid all Federal and other material taxes, assessments,  fees and
other  governmental  charges  levied or imposed  upon them or their  properties,
income  or  assets  otherwise  due and  payable  except  those  which  are being
contested  in good  faith by  appropriate  proceedings  and for  which  adequate
reserves have been  provided in  accordance  with GAAP and no Notice of Lien has
been filed or recorded. There is no proposed tax assessment against the Borrower
or any of its  Subsidiaries  which would,  if the assessment  were made,  have a
Material Adverse Effect.

         SECTION 4.10.  Financial Condition.

          (a) The audited  consolidated  statements of financial position of the
Borrower  and  its  Subsidiaries  dated  December  31,  1996,  and  the  related
consolidated  statements  of loss,  stockholders'  equity and cash flows for the
fiscal  year ended on that  date:  (i) were  prepared  in  accordance  with GAAP
consistently applied throughout the periods covered thereby, except as otherwise
expressly noted therein,  (ii) fairly  present,  in all material  respects,  the
financial  condition of the Borrower and its Subsidiaries as of the date thereof
and  results of  operations  for the period  covered  thereby and (iii) show all
material  Indebtedness  and  other  liabilities,  direct or  contingent,  of the
Borrower and its  consolidated  Subsidiaries  as of the date thereof  (including
liabilities for taxes and material commitments).

          (b) The  unaudited pro forma summary  consolidated  condensed  balance
sheet of the Borrower and its  Subsidiaries  as of September  30, 1997  together
with the related pro forma summary  condensed  statement of operations  data for
the nine months then ended fairly present,  in conformity with GAAP applied on a
basis  consistent  with the financial  statements  referred to in subsection (a)
above, the consolidated  financial position of the Borrower and its Subsidiaries
as of such date, based on the assumptions set forth therein. As of such date and
the Closing  Date,  the Borrower and its  Subsidiaries  had and have no material
liabilities,  contingent or otherwise,  which are not properly reflected on such
balance sheet (including liabilities for taxes and material commitments).

          (c) Since  September  30,  1997,  there has been no  Material  Adverse
Effect.

         SECTION 4.11. Environmental Matters. The operations of the Borrower and
each of its Subsidiaries  comply in all material respects with all Environmental
Laws.  The Borrower and each of its  Subsidiaries  have  obtained all  licenses,
permits,  authorizations and registrations  required under any Environmental Law
("Environmental Permits") necessary for its operations to comply in all material




                                       36





respects with Environmental Laws, and all such Environmental Permits are in full
force and effect,  and the Borrower and each of its Subsidiaries are in material
compliance with all terms and conditions of such Environmental  Permits. None of
the  Borrower,  any of its  Subsidiaries  or any of  their  present  or,  to the
knowledge  of the  Borrower,  past  property  or  operations  is  subject to any
outstanding  written order from or agreement with any Governmental  Authority or
other  Person,  nor  subject  to  any  judicial  or  administrative  proceeding,
respecting any Environmental  Law,  Environmental  Claim or Hazardous  Material.
There  are  no  conditions  or   circumstances   which  may  give  rise  to  any
Environmental  Claim  arising  from  the  operations  of  the  Borrower  or  its
Subsidiaries,  including  Environmental Claims associated with any operations of
the  Borrower  or its  Subsidiaries,  with a  potential  liability  in excess of
$5,000,000 in the aggregate.  Without  limiting the generality of the foregoing,
the Borrower and its Subsidiaries have met all notification  requirements  under
Title III of the Superfund  Amendments  and  Reauthorization  Act of 1986 or any
other Environmental Law.

         SECTION 4.12.  Regulated  Entities.  None of the  Borrower,  any Person
controlling  the Borrower,  or any  Subsidiary  thereof,  is (a) an  "Investment
Company"  within  the  meaning of the  Investment  Company  Act of 1940;  or (b)
subject to regulation  under the Public Utility Holding Company Act of 1935, the
Federal Power Act, the Interstate  Commerce Act, any state public utilities code
or any other  Federal or state  statute or  regulation  limiting  its ability to
incur Indebtedness.

         SECTION 4.13.  Subsidiaries.  As of the Closing Date, the Borrower does
not have any Subsidiaries and has no equity investments in any other corporation
or entity.

         SECTION  4.14.  Insurance.  The  properties  of the  Borrower  and  its
Subsidiaries  are  insured  with  financially  sound  and  reputable   insurance
companies,  in such amounts, with such deductibles and covering such risks as is
customarily  carried on by companies  engaged in similar  businesses  and owning
similar properties in localities where the Borrower or such Subsidiary operates.

         SECTION  4.15.  Business.  The Borrower and its  Subsidiaries  have not
conducted  any business  other than as  described  in the  Offering  Memorandum.
Neither the business nor the properties of the Borrower and its Subsidiaries are
or have been affected by any fire, explosion, accident, strike, lockout or other
labor dispute,  drought, storm, hail, earthquake,  embargo, act of God or of the
public enemy or other casualty  (whether or not covered by insurance)  which has
had a Material Adverse Effect.

         SECTION 4.16.  Collateral; Property. All contracts and all property now
owned by the  Borrower  are held by it free and  clear of all Liens  other  than





                                       37





Permitted Liens. The Borrower has good, marketable and valid title in and to all
of the  Collateral  now  owned by it,  in each  case free and clear of all Liens
other than Permitted Liens.

         SECTION 4.17.  Security and Pledge  Agreement.  The Security and Pledge
Agreement  creates  in favor of the  Administrative  Agent,  for the  equal  and
ratable (except as expressly  provided  therein) benefit of the Secured Parties,
legal,  valid and enforceable Liens on or in all of the Collateral to the extent
that such  Liens may  legally be given and be  effective  and  enforceable.  All
filings, recordations, registrations and other actions necessary to perfect such
Liens have been duly effected, and, to the extent that such Liens may legally be
given and be effective  and  enforceable,  each Lien created by the Security and
Pledge Agreement  constitutes a perfected Lien on or in all right, title, estate
and  interest  of the  Borrower in the  Collateral  covered  thereby,  prior and
superior to all other Liens except  Permitted Liens arising by operation of law,
and all necessary  and  appropriate  consents to the creation and  perfection of
such Liens have been obtained.

         SECTION  4.18.   Disclosure.   The  information   (including,   without
limitation,  the information in the Offering Memorandum) furnished in writing at
or prior to the Closing Date by the Borrower to any Agent or Bank in  connection
with this Agreement and the transactions  contemplated  hereby is true, complete
and accurate in every material  respect or based on reasonable  estimates on the
date as of which such  information  is stated or certified and is not incomplete
by omitting to state any material fact necessary to make such information (taken
as a whole)  not  misleading  in light of the  circumstances  under  which  such
information  was made.  The pro forma  financial  projections  contained  in the
Offering  Memorandum were made in good faith and the assumptions on the basis of
which such  projections  were made were  (when  made) and are (as of the date of
this Agreement)  reasonable.  There is no fact known to the Borrower on the date
as of which this representation and warranty is made that has not been disclosed
in writing to the Agent  which could  reasonably  be expected to have a Material
Adverse Effect.



                                    ARTICLE 5
                                    COVENANTS

         The  Borrower  agrees  that,  so long as any  Bank  has any  Commitment
hereunder or any amount payable hereunder or under any Note remains unpaid:

         SECTION  5.01.  Information.  The Borrower will deliver to each of the
Banks:




                                       38





          (a) as soon as available,  but not later than 90 days after the end of
each  fiscal  year of the  Borrower,  commencing  with the  fiscal  year  ending
December  31,  1997, a copy of the audited  consolidated  balance  sheets of the
Borrower  as at the  end of  such  year  and the  related  audited  consolidated
statements of income,  stockholders' equity and cash flows for such fiscal year,
setting  forth in each case in  comparative  form the figures  for the  previous
year,  and  accompanied  by the  opinion  of  Arthur  Andersen  LLP  or  another
nationally-recognized  independent  public  accounting  firm which  report shall
state  that  such  consolidated  financial  statements  present  fairly,  in all
material respects, the financial position,  results of operations and cash flows
for the periods  indicated in conformity with GAAP applied on a basis consistent
with prior years;

          (b) as soon as available,  but not later than 45 days after the end of
each of the first three fiscal quarters of each year,  commencing with the first
such fiscal  quarter to end after the  Effective  Date, a copy of the  unaudited
consolidated  balance  sheets of the  Borrower as of the end of such quarter and
the related  consolidated  statements of income,  stockholders'  equity and cash
flows for the period  commencing  on the first day and ending on the last day of
such quarter,  and  certified by an  appropriate  Responsible  Officer as fairly
presenting,  in all material  respects,  in accordance with GAAP (except for the
absence of  footnote  disclosure),  the  financial  position  and the results of
operations of the Borrower; and

          (c) as soon as available,  any other interim  financial  statements of
the Borrower and its  Subsidiaries  reasonably  requested by the  Administrative
Agent at the direction of the Required Banks.

         SECTION  5.02.   Certificates;  Other  Information.  The Borrower  will
deliver to each of the Banks:

          (a)  concurrently  with  the  delivery  of  the  financial  statements
referred to in Section 5.01(a) above, a certificate of the independent certified
public accountants reporting on such financial statements stating that in making
the examination  necessary  therefor no knowledge was obtained of any Default or
Event of Default, except as specified in such certificate;

          (b)  concurrently  with  the  delivery  of  the  financial  statements
referred to in Section 5.01(a) above, a certificate of a Responsible  Officer of
the Borrower (i) stating  that,  to the best of such  officer's  knowledge,  the
Borrower, during such period, has observed or performed all of its covenants and
other agreements,  and satisfied every condition  contained in this Agreement to
be observed, performed or satisfied by it, and that such officer has obtained no
knowledge  of any  Default  or Event of  Default  except  as  specified  in such





                                       39




certificate, (ii) when applicable, showing in detail the calculations supporting
such  statement in respect of Article 5 and (iii)  setting forth the Excess Cash
Flow for such  period,  together  with the  calculation  thereof  in  reasonable
detail;

          (c) promptly  after the same are filed,  copies of (if, in the case of
reports to the FCC,  such reports are material)  all  financial  statements  and
regular,  periodical or special  reports which the Borrower or any Subsidiary of
the Borrower may make to, or file with, the Securities and Exchange  Commission,
the FCC or any successor or similar Governmental Authorities; and

          (d) promptly,  such additional  financial and other information as the
Administrative  Agent,  at the  request  of any  Bank,  may  from  time  to time
reasonably request.

          SECTION 5.03.  Notices.  The Borrower shall promptly notify the Agents
and each Bank of:

          (a) the  occurrence  of any  Default or Event of  Default,  and of the
occurrence or existence of any event or  circumstance  that could  reasonably be
expected to become a Default or Event of Default;

          (b) any (i) breach or  non-performance  of, or any  default  under any
Contractual  Obligation  which  could  reasonably  be  expected  to  result in a
Material Adverse Effect; or (ii) dispute, litigation, investigation,  proceeding
or  suspension  which may exist at any time  between the  Borrower or any of its
Subsidiaries and any Governmental  Authority and which, if determined  adversely
to the  Borrower or any of its  Subsidiaries,  could  reasonably  be expected to
result in a Material Adverse Effect;

          (c)  the  commencement  of,  or  any  material   development  in,  any
litigation or proceeding  affecting the Borrower or any  Subsidiary (i) in which
the  amount of damages  claimed  is  $5,000,000  (or its  equivalent  in another
currency or currencies) or more,  (ii) in which  injunctive or similar relief is
sought and which, if adversely determined, could have a Material Adverse Effect,
or (iii) in which  the  relief  sought  is an  injunction  or other  stay of the
performance of any Loan Document or the operations of the Borrower or any of its
Subsidiaries;

          (d) upon, but in no event later than ten days after, becoming aware of
(i)  any  and  all  enforcement,  cleanup,  removal  or  other  governmental  or
regulatory actions  instituted,  completed or threatened against the Borrower or
any  Subsidiary  or  any  of  their   properties   pursuant  to  any  applicable
Environmental   Laws,  (ii)  all  other   Environmental   Claims  or  (iii)  any
environmental  or similar  condition  on any real  property  adjoining or in the





                                       40




vicinity of the property of the Borrower or any of its  Subsidiaries  that could
reasonably  be  anticipated  to cause such  property  or any part  thereof to be
subject to any restrictions on the ownership, occupancy,  transferability or use
of such property under any Environmental Laws;

          (e) any other  litigation or proceeding  affecting the Borrower or any
of its  Subsidiaries  which  the  Borrower  would be  required  to report to the
Securities and Exchange  Commission  pursuant to the Securities  Exchange Act of
1934,  within four days after  reporting the same to the Securities and Exchange
Commission;

          (f) any  ERISA  Event  affecting  the  Borrower  or any  member of its
Controlled  Group (but in no event  more than ten days  after such ERISA  Event)
together  with (i) a copy of any notice  with  respect to such ERISA Event filed
with the PBGC and (ii) any notice  delivered  by the PBGC to the Borrower or any
member or its Controlled Group with respect to such ERISA Event;

          (g) any Material  Adverse  Effect  subsequent  to the date of the most
recent  audited  financial  statements  of the  Borrower  delivered to the Banks
pursuant to Section 5.01(a);

          (h) any material change in accounting  policies or financial reporting
practices;

          (i) any labor controversy resulting in or threatening to result in any
strike,  work stoppage,  boycott,  shutdown or other labor disruption against or
involving the Borrower or any Subsidiary;

          (j)   any material revision of the Borrower's business plan;

          (k) the adoption of each capital expenditures budget by the Borrower;

          (l) any event that could  reasonably be expected to result in Net Cash
Proceeds requiring a mandatory prepayment pursuant to Section 2.04; and

          (m) the  delivery  of, or receipt of, any notice of (i) a reduction in
coverage of any insurance required to be maintained by Section 5.06 or otherwise
procured by the Borrower covering loss or damage to any material property of the
Borrower (other than a reduction in coverage or amount  resulting from a payment
thereunder)  or (ii) the  cancellation  or  non-renewal  of any  such  insurance
policy.

Each  notice  pursuant  to this  Section  shall be  delivered  promptly  after a
Responsible Officer becomes aware of the subject matter of such notice and shall
be accompanied by a written  statement by a Responsible  Officer of the Borrower





                                       41




setting forth details and effective date of the  occurrence  referred to therein
and stating what action the Borrower proposes to take with respect thereto.

         SECTION 5.04. Conduct of Business; Preservation of Corporate Existence.
The Borrower shall, and shall cause each of its  Subsidiaries:  (a) to engage in
business of the same  general  type as now  conducted  by the  Borrower  and its
Subsidiaries  (including  ARDIS  and  AMRC  Holdings  and  Subsidiaries  of AMRC
Holdings);  (b) to preserve and maintain in full force and effect its  corporate
existence  and good  standing  under  the laws of its State or  jurisdiction  of
incorporation; (c) to preserve and maintain in full force and effect all rights,
privileges,  qualifications,  permits,  licenses  and  franchises  necessary  or
desirable  in the normal  conduct  of its  business;  (d) to use its  reasonable
efforts,  in the ordinary course and consistent with past practice,  to preserve
its  business  organization  and  preserve  the  goodwill  and  business  of the
customers,  suppliers and others having  business  relations with it; and (e) to
preserve  or renew all of its  registered  trademarks,  trade  names and service
marks, the non-preservation of which could have a Material Adverse Effect.

         SECTION 5.05. Maintenance of Property. The Borrower shall maintain, and
shall cause each of its Principal  Subsidiaries and Subsidiaries,  respectively,
to  maintain,  and  preserve  all its  property  which is used or  useful in its
business in good working order and condition, ordinary wear and tear excepted.

         SECTION 5.06.  Maintenance of Insurance.  The Borrower shall, and shall
cause each of its  Subsidiaries  (other than AMRC Holdings and  Subsidiaries  of
AMRC  Holdings) to,  maintain in full force and effect at all times on and after
the  Effective  Date property  insurance  with  financially  sound and reputable
insurance  companies,  in such amounts,  with such deductibles and covering such
risks as is customarily  carried by companies engaged in similar  businesses and
owning similar  properties in localities  where the Borrower or such  Subsidiary
operates:

         SECTION 5.07.  Payment of Obligations.  The Borrower  shall,  and shall
cause each of its Principal Subsidiaries and Subsidiaries, respectively, to, pay
and discharge as the same shall become due and payable,  all its obligations and
liabilities,  including:  (a) all tax liabilities,  assessments and governmental
charges or levies upon it or its properties or assets, unless the same are being
contested in good faith by  appropriate  proceedings  and  adequate  reserves in
accordance with GAAP are being maintained by such Person;  (b) all lawful claims
which, if unpaid, might by law become a Lien upon its property (excluding claims
being contested in good faith by the Borrower,  and for which adequate  reserves
have been made or as to which the corresponding liens have been bonded); and (c)





                                       42




all  Indebtedness  as and when due and payable but subject to any  subordination
provisions   contained  in  any   instrument   or  agreement   evidencing   such
Indebtedness.

         SECTION 5.08.  Compliance  with Laws.  The Borrower  shall comply,  and
shall cause each of its  Subsidiaries to comply,  in all material  respects with
all Requirements of Law of any Governmental  Authority having  jurisdiction over
it or its business  (including the Federal Fair Labor  Standards Act and ERISA),
except such as may be contested in good faith or as to which a bona fide dispute
may exist.

         SECTION  5.09.  Inspection  of  Property  and  Books and  Records.  The
Borrower shall maintain, and shall cause each of its Subsidiaries, respectively,
to maintain, proper books of record and account, in which full, true and correct
entries  in  conformity  with  GAAP  consistently  applied  shall be made of all
financial  transactions  and matters  involving  the assets and  business of the
Borrower and such Subsidiaries. The Borrower will permit, and will cause each of
its  Subsidiaries to permit,  representatives  of any Agent or Bank to visit and
inspect any of its properties, to examine its corporate, financial and operating
records  and make  copies  thereof or  abstracts  therefrom,  and to discuss its
affairs,  finances and accounts  with its  directors,  officers,  employees  and
independent  public  accountants at such reasonable times during normal business
hours and as often as may be reasonably desired,  upon reasonable advance notice
to the Borrower;  provided that when an Event of Default exists  representatives
from the United States offices of any Agent or Bank may visit and inspect at the
expense of the Borrower such  properties at any time during  business  hours and
without  advance  notice.  The Borrower shall reimburse the Agents and the Banks
for  their   reasonable   expenses   incurred  in  conducting  such  visits  and
examinations when an Event of Default exists.

         SECTION 5.10.  Environmental Laws.  (a) The  Borrower shall,  and shall
cause each of its  Subsidiaries to, conduct its operations and keep and maintain
its property in compliance with all Environmental Laws.

          (b) Upon  written  request of any Agent or Bank,  the  Borrower  shall
submit and cause each of its  Subsidiaries to submit,  to such Agent or Bank, at
the Borrower's sole cost and expense at reasonable intervals, a report providing
an update of the status of and any  environmental,  health or safety  compliance
obligation, remedial obligation or liability, that could, individually or in the
aggregate, result in liability in excess of $5,000,000.

         SECTION 5.11.  Use of Proceeds.  The Borrower shall use the proceeds of
the Loans only to refinance  obligations  under the Hughes Bridge Loan Agreement
and the  Existing  Credit  Facilities.  No  portion  of the Loans  will be used,





                                       43




directly or  indirectly,  for the  purpose,  whether  immediate,  incidental  or
ultimate,  of buying or  carrying  any  "margin  stock"  within  the  meaning of
Regulation  U. No proceeds of any Loans will be used to acquire any  security in
any transaction which is subject to Section 13 or 14 of the Securities  Exchange
Act of 1934, as amended.

         SECTION 5.12. Security and Pledge Agreement.  The Borrower shall at all
times ensure that (i) the Security and Pledge Agreement  creates in favor of the
Administrative  Agent, for the equal and ratable benefit of the Secured Parties,
legal, valid and enforceable Liens on or in all Collateral covered thereby; (ii)
all  filings,  recordations,   registrations  and  other  actions  necessary  or
desirable  to  perfect  the Liens  created  or  purported  to be  created by the
Security and Pledge  Agreement have been duly effected;  (iii) each Lien created
by the Security and Pledge  Agreement  constitutes a perfected Lien on or in all
right,  title,  estate and  interest  of the  Borrower,  as  applicable,  in the
Collateral,  prior and superior to all Liens other than Permitted  Liens arising
by operation  of law; and (iv) all  necessary  and  appropriate  consents to the
creation and  perfection  of the Liens created or purported to be created by the
Security and Pledge Agreement have been obtained.

         SECTION  5.13.   No  Subsidiaries.  The  Borrower  shall  not  have any
Subsidiaries or equity  investments in any other corporation or entity except as
set forth on Schedule 4.13.

         SECTION 5.14. FCC Approval. The Borrower shall take any action that the
Administrative Agent may reasonably request in order to obtain from the FCC such
approval (other than relief from the FCC's alien ownership  restrictions) as may
be necessary to enable the  Administrative  Agent to exercise and enjoy the full
rights and  benefits  granted to the  Administrative  Agent by the  Security and
Pledge Agreement and each other agreement,  instrument and document delivered to
the Administrative  Agent in connection  therewith.  The Borrower shall, without
limitation,  also use diligent efforts,  at the expense of the Borrower,  (a) to
assist the Administrative  Agent in obtaining approval of the FCC for any action
or  transaction  contemplated  by the  Borrower's  business plan included in the
Offering  Memorandum for which such approval is or shall be required by law, and
(b) upon request of the Administrative Agent, to prepare, sign and file with the
FCC the assignor's or  transferor's  portion of any  application or applications
for consent to the assignment of any license or transfer or control necessary or
appropriate  under the FCC's rules and  regulations  for approval of any sale or
sales of any Collateral or any assumption by the Administrative  Agent of voting
rights  relating  thereto  effected in accordance with the terms of the Security
and Pledge Agreement.

         SECTION 5.15.   Government  Approvals.  The Borrower  shall,  and shall
cause each of its Subsidiaries to, comply with the terms of and maintain in full





                                       44




force and effect the FCC Licenses,  and all amendments  thereto,  and shall, and
shall cause each of its  Subsidiaries  to, obtain,  maintain and comply with the
terms of all other  Government  Approvals which are necessary  under  applicable
laws and  regulations  in connection  with the  Borrower's or such  Subsidiary's
business.  No such  Government  Approval  shall be subject  to any  restriction,
condition,  limitation  or other  provision  that would have a Material  Adverse
Effect.

         SECTION 5.16.  Further Assurances.

          (a) The Borrower shall ensure that all written  information,  exhibits
and  reports  furnished  to the  Banks do not and will not  contain  any  untrue
statement of a material  fact and do not and will not omit to state any material
fact or any  fact  necessary  to  make  the  statements  contained  therein  not
misleading  in  light of the  circumstances  in which  made,  and will  promptly
disclose to the Agents and the Banks and correct any defect or error that may be
discovered therein or in any Loan Document or in the execution,  acknowledgement
or recordation thereof.

          (b) Promptly upon written request by the  Administrative  Agent or the
Required Banks,  the Borrower shall (and shall cause any of its Subsidiaries to)
do, execute,  acknowledge,  deliver, record, re-record,  file, re-file, register
and re-register,  any and all such further acts,  deeds,  conveyances,  security
agreements, mortgages, assignments, estoppel certificates,  financing statements
and  continuations  thereof,  termination  statements,  notices  of  assignment,
transfers, certificates,  assurances and other instruments as the Administrative
Agent or such  Banks may  reasonably  require  from time to time in order (i) to
carry out more  effectively  the  purposes of this  Agreement  or any other Loan
Document,  (ii) to  subject  to the Liens  created  by the  Security  and Pledge
Agreement any of the properties,  rights or interests covered thereby,  (iii) to
perfect and maintain the  validity,  effectiveness  and priority of the Security
and Pledge Agreement and the Liens intended to be created  thereby,  and (iv) to
better assure, convey, grant, assign, transfer, preserve, protect and confirm to
the  Administrative  Agent and  Banks the  rights  granted  or now or  hereafter
intended to be granted to the Banks  under any Loan  Document or under any other
instrument executed in connection therewith.

         SECTION 5.17.  Limitation on Liens.  The Borrower  shall not, and shall
not permit any other member of the Borrower  Group to,  directly or  indirectly,
make, create,  incur, assume or suffer to exist any Lien upon or with respect to
any part of its property or assets,  whether now owned or hereafter acquired, or
offer or agree to do so, other than the following ("Permitted Liens"):




                                       45





          (a) any Lien  existing on the  Effective  Date  securing  Indebtedness
existing on the Effective Date and identified on Schedule 5.17;

          (b) any Lien in favor of the  Administrative  Agent  created under any
Loan Document and any Lien in favor of the  Shareholder  Guarantors  pursuant to
the Shareholder Guarantor Security Agreement;

          (c) Liens for taxes, fees,  assessments or other governmental  charges
which are not delinquent or remain  payable  without  penalty,  or to the extent
that non-payment  thereof is permitted by Section 5.07,  provided that no Notice
of Lien has been filed or recorded;

          (d) carriers', warehousemen's,  mechanics', landlords', materialmen's,
repairmen's  or other similar  Liens arising in the ordinary  course of business
which do not  secure  Indebtedness  and are not  delinquent  or  remain  payable
without penalty;

          (e) Liens  (other than any Lien  imposed by ERISA) on the  property of
any member of the Borrower Group incurred,  or pledges or deposits required,  in
connection with workmen's compensation,  unemployment insurance and other social
security legislation;

          (f) Liens on the property of any member of the Borrower Group securing
(i) the performance of bids,  trade contracts  (other than for borrowed  money),
leases, statutory obligations,  and (ii) obligations on surety and appeal bonds,
and (iii) other  obligations of a like nature incurred in the ordinary course of
business which do not secure  Indebtedness,  provided that all such Liens in the
aggregate could not cause a Material Adverse Effect;

          (g)   easements,   rights-of-way,   restrictions   and  other  similar
encumbrances  incurred  in  the  ordinary  course  of  business  which,  in  the
aggregate,  are  not  substantial  in  amount,  and  which  do not  in any  case
materially  detract from the value of the property  subject thereto or interfere
with the ordinary conduct of the businesses of the Borrower Group;

          (h)  Liens  on any  asset  which is the  subject  of a  capital  lease
securing  Indebtedness  incurred or assumed for the purpose of financing  all or
any  part of the cost of  acquiring  such  asset,  provided  that (x) such  Lien
attaches  concurrently with or within 30 days after the acquisition thereof, and
(y) the sum of the aggregate  principal amount of such  Indebtedness  secured by
such Liens shall not exceed $15,000,000;





                                       46





          (i) Liens on contract rights under  subscriber  equipment leases sold,
pledged or  otherwise  transferred  pursuant to any bona fide  financing of such
leases;

          (j)  Liens  on  property   and  assets  of  AMRC   Holdings   and  its
Subsidiaries; and

          (k) Liens to secure Vendor Financing Indebtedness permitted by Section
5.25(k) provided that such Liens cover only the assets acquired with such Vendor
Financing Indebtedness.

         SECTION 5.18.  Disposition of Assets,  Consolidations and Mergers.  The
Borrower  shall  not,  and shall not  permit  any  Subsidiary  (other  than AMRC
Holdings and  Subsidiaries  of AMRC Holdings) to,  directly or  indirectly,  (i)
sell, assign, lease, convey, transfer or otherwise dispose of (whether in one or
a series of  transactions)  any of its assets,  business or property  (including
accounts  and  notes  receivable  (with  or  without   recourse)  and  equipment
sale-leaseback transactions) or (ii) merge or consolidate with any other Person,
or enter into any agreement to do any of the foregoing  described in clauses (i)
or (ii) except for the following;  provided that immediately after giving effect
to any of the following, no Default or Event of Default would exist:

          (a) sales,  transfers,  or other  dispositions of inventory,  or used,
worn-out or surplus property,  or property of no further use to the Borrower and
its Subsidiaries, all in the ordinary course of business;

          (b)  sales,  transfers,  or other  dispositions  of  equipment  in the
ordinary  course of business to the extent that such  equipment is exchanged for
credit  against  the  purchase  price of similar  replacement  equipment  or the
proceeds of such sale are reasonably  promptly  applied to the purchase price of
such replacement equipment;

          (c)  sales,   transfers,   or  other  dispositions  of  communications
services, capacity or equipment pursuant to the customer contracts providing for
the sale of  communications  services,  capacity or  equipment  in the  ordinary
course of business;

          (d)  sales,  transfers  or other  dispositions  pursuant  to bona fide
sale-leaseback  financings in which the lease gives rise solely to Capital Lease
Obligations;  provided,  however,  that  any  such  sales,  transfers  or  other
dispositions are not permitted with any assets of the communications network;

          (e) sales,  transfers, or other dispositions of assets in the ordinary
course of business having a fair market value not exceeding $500,000 per item or





                                       47




$1,000,000 in the aggregate in any fiscal year (excluding  sales,  transfers and
dispositions  theretofore  approved in accordance  with the terms hereof in such
fiscal year);

          (f)  sales,  transfers  or  other  dispositions  of  assets  to  Sales
Corporation to be used in connection with the sales and marketing of services of
AMSC Acquisition Company and having a fair market value not exceeding $5,000,000
in the aggregate during the term of this Agreement;

          (g) sales,  transfers or other  dispositions  of contract rights under
subscriber equipment leases pursuant to any bona fide financing of such leases;

          (h) non-exclusive licenses of technology and other intangible assets;

          (i) sales of mobile earth terminals and related  equipment,  and other
inventory;

          (j) any  Subsidiary of the Borrower may merge,  consolidate or combine
with or into, or transfer assets to the Borrower or one or more  Subsidiaries of
the Borrower;  provided that with respect to any such transaction  involving the
Borrower,  the Borrower shall be the continuing or surviving  corporation and if
any  such  transaction   shall  be  between  a  Subsidiary  and  a  wholly-owned
Subsidiary,  the  wholly-owned  Subsidiary  shall be the continuing or surviving
corporation;

          (k) any  Subsidiary  of the  Borrower  may sell,  lease,  transfer  or
otherwise  dispose of any or all of its assets (upon  voluntary  liquidation  or
otherwise), to the Borrower or another wholly-owned Subsidiary of the Borrower;

          (l) the Borrower or any Subsidiary  may merge,  consolidate or combine
with another  entity if the  Borrower or the  Subsidiary,  respectively,  is the
corporation surviving the merger; and

          (m)   the Satellite Lease Arrangements.

         SECTION 5.19. Employee Contracts and Arrangements. Neither the Borrower
nor  any of its  Subsidiaries  will  enter  into  any  employment  contracts  or
arrangements whose terms,  including salaries,  benefits and other compensation,
are not normal and customary and  commercially  reasonable for companies of like
size and circumstances.

         SECTION 5.20.  Investments.  Neither  the Borrower nor any other member
of the Borrower  Group will make or acquire any  Investment  in any Person other
than:




                                       48





          (a) Investments in Persons which are Subsidiaries on the date hereof;

          (b) Cash Equivalents; and

          (c) any Investment not otherwise permitted by the foregoing clauses of
this Section if,  immediately  after such  Investment  is made or acquired,  the
aggregate  net book value of all  Investments  permitted by this clause (c) does
not exceed $10,000,000.

         SECTION 5.21. Transactions with Affiliates. Except where such Affiliate
is a member of the Borrower  Group,  the Borrower  will not, and will not permit
any  Subsidiary  to,  directly  or  indirectly,  (i) pay any funds to or for the
account of any Affiliate,  (ii) make any investment in any Affiliate (whether by
acquisition of stock or indebtedness,  by loan,  advance,  transfer of property,
guarantee  or  other  agreement  to  pay,  purchase  or  service,   directly  or
indirectly,  any Indebtedness,  or otherwise),  (iii) lease,  sell,  transfer or
otherwise dispose of any assets,  tangible or intangible,  to any Affiliate,  or
(iv) participate in, or effect,  any transaction  with any Affiliate,  except in
each  case on an  arm's-length  basis on terms  at  least  as  favorable  to the
Borrower or such  Subsidiary as could have been obtained from a third party that
was not an  Affiliate  or as  otherwise  expressly  approved  in  writing by the
Required Banks.

         SECTION 5.22. Compliance with ERISA. The Borrower shall not directly or
indirectly,  and shall not permit any member of the Controlled Group directly or
indirectly (i) to terminate, any Qualified Plan subject to Title IV of ERISA, so
as to result in any material (in the opinion of the Required Banks) liability to
the Borrower or any member of the Controlled  Group, (ii) to permit to exist any
ERISA  Event,  which  presents  the risk of a  material  (in the  opinion of the
Required  Banks)  liability of any member of the Controlled  Group,  or (iii) to
make a complete or partial withdrawal (within the meaning of ERISA Section 4201)
from any  Multiemployer  Plan so as to result in any material (in the opinion of
the  Required  Banks)  liability to any member of the  Controlled  Group or (iv)
permit the  present  value of all  nonforfeitable  accrued  benefits  under each
Qualified  Plan  (using  the  actuarial  assumptions  utilized  by the PBGC upon
termination  of a Qualified  Plan)  materially  (in the opinion of the  Required
Banks) to exceed the fair market  value of  Qualified  Plan assets  allocable to
such benefits, all determined as of the most recent valuation date for each such
Qualified Plan.

         SECTION  5.23.  Restricted  Payments.  The Borrower will not declare or
make any dividend  payment or other  distribution of assets,  properties,  cash,
rights,  obligations  or securities on account of any shares of any class of its
capital stock or purchase,  redeem or otherwise acquire for value (or permit any





                                       49




member of the  Borrower  Group to do so) any shares of its capital  stock or any
warrants,   rights  or  options  to  acquire  such  shares,   now  or  hereafter
outstanding.

         SECTION 5.24.  Accounting Changes.  The Borrower will not, and will not
permit any Subsidiary to, make any  significant  change in accounting  treatment
and reporting  practices,  except as required by GAAP, or change the fiscal year
of the Borrower or any of its Subsidiaries.

         SECTION 5.25.  Limitation on Indebtedness.  The Borrower shall not, and
shall not permit any Subsidiary  (other than AMRC Holdings and  Subsidiaries  of
AMRC  Holdings)  to,  create,  incur,  assume,  guaranty,  suffer to  exist,  or
otherwise  become or remain  directly or indirectly  liable with respect to, any
Indebtedness, except for:

          (a)  accounts  payable to trade  creditors  for goods and services and
current  operating  liabilities  (not the  result  of the  borrowing  of  money)
incurred in the ordinary course of the Borrower's or the Subsidiary's  business,
as the case may be, in  accordance  with  customary  terms and paid  within  the
specified time,  unless  contested in good faith by appropriate  proceedings and
reserved for in accordance with GAAP;

          (b)   Indebtedness represented by Rate Contracts;

          (c)   income taxes payable and deferred taxes;

          (d)   accrued expenses and deferred income;

          (e)  Indebtedness  under the Senior  Notes in an  aggregate  principal
amount not to exceed $335,000,000 and Contingent Obligations of the Borrower and
of AMSC Acquisition  Company's  Subsidiaries in respect thereof (such Contingent
Obligations  of the  Borrower to be  subordinated  as  described in the Offering
Memorandum);

          (f)   Indebtedness under the Revolving Credit Agreement;

          (g)  Contingent  Obligations  incurred  in  connection  with any lease
financing of mobile  communications  terminals,  not exceeding $5,000,000 in the
aggregate in principal amount;

          (h)  Indebtedness  outstanding on the Effective Date and identified on
Schedule 5.25;





                                       50





          (i) Indebtedness under the Financial Management Account Line of Credit
of the Borrower  payable to the order of Wachovia Bank of North Carolina,  N.A.,
in an aggregate principal amount at any time not exceeding $2,500,000; and

          (j)  Indebtedness   incurred  to  finance  in-orbit  insurance  in  an
aggregate amount outstanding at any time not to exceed $6,000,000;

          (k) Vendor Financing  Indebtedness in an aggregate amount  outstanding
at any time not to exceed $10,000,000; and

          (l) any other Indebtedness incurred after the Effective Date; provided
that the aggregate  outstanding  principal amount of all such Indebtedness shall
not at any time exceed $15,000,000.



                                    ARTICLE 6
                                    DEFAULTS

          SECTION  6.01.  Events  of  Default.  If one or more of the  following
events ("Events of Default") shall have occurred and be continuing:

          (a) the Borrower  shall fail to pay any principal of any Loan when due
or any  interest,  any fees or any other  amount  payable  hereunder  within two
Business Days of the date when due, or one or more Shareholder  Guarantors shall
have made more than two capital  contributions or Investments in the Borrower or
any Subsidiary thereof (or more than one during any twelve-month period) for the
principal  purpose of permitting  the Borrower to pay any  principal,  interest,
fees or other amounts payable hereunder;

          (b) the  Borrower  shall  fail to  observe  or  perform  any  covenant
contained  in Article 5, other than those  contained  in Sections  5.01  through
5.05, 5.07 through 5.10 and 5.16;

          (c) the  Borrower  shall fail to observe or perform  any  covenant  or
agreement contained in this Agreement (other than those covered by clause (a) or
(b) above) for 20 days after  notice  thereof has been given to the  Borrower by
the Administrative Agent at the request of any Bank;

          (d) any representation,  warranty,  certification or statement made by
the Borrower or a Subsidiary of the Borrower in this Agreement or any other Loan
Document or in any certificate, financial statement or  other document delivered




                                       51





pursuant to this  Agreement  shall prove to have been  incorrect in any material
respect when made (or deemed made);

          (e) the Borrower or any  Subsidiary of the Borrower shall fail to make
any  payment  in  respect  of (x) any  obligation  under  the  Revolving  Credit
Agreement  or (y) any other  Indebtedness  or  Contingent  Obligation  having an
aggregate  principal and face amount of more than $5,000,000,  in each case when
due (whether by scheduled maturity, required prepayment, acceleration, demand or
otherwise)  and such  failure  continues  after the  applicable  grace period or
notice period, if any, specified in the document relating thereto;

          (f)  any  event  or  condition   shall  occur  which  results  in  the
acceleration of the maturity of any  Indebtedness  or Contingent  Obligation (x)
under the Revolving Credit Agreement or (y) any other Indebtedness or Contingent
Obligation of the Borrower or any Subsidiary of the Borrower having an aggregate
principal or face amount of more than $5,000,000 or enables (or, with the giving
of  notice  or lapse of time or  both,  would  enable)  the  holder  of any such
Indebtedness  or  Contingent  Obligation  or any Person  acting on such holder's
behalf to accelerate the maturity thereof;

          (g)  the  Borrower  or  any  Principal  Subsidiary  shall  commence  a
voluntary case or other proceeding seeking liquidation,  reorganization or other
relief with respect to itself or its debts under any  bankruptcy,  insolvency or
other  similar law now or  hereafter in effect or seeking the  appointment  of a
trustee, receiver, liquidator,  custodian or other similar official of it or any
substantial part of its property,  or shall consent to any such relief or to the
appointment of or taking  possession by any such official in an involuntary case
or other proceeding commenced against it, or shall make a general assignment for
the  benefit  of  creditors,  or shall fail  generally  to pay its debts as they
become  due,  or  shall  take  any  corporate  action  to  authorize  any of the
foregoing;

          (h) an involuntary case or other proceeding shall be commenced against
the Borrower or any Principal Subsidiary seeking liquidation,  reorganization or
other relief with respect to it or its debts under any bankruptcy, insolvency or
other  similar law now or  hereafter in effect or seeking the  appointment  of a
trustee, receiver, liquidator,  custodian or other similar official of it or any
substantial part of its property,  and such involuntary case or other proceeding
shall remain  undismissed  and unstayed for a period of 60 days; or an order for
relief shall be entered against the Borrower or any Principal  Subsidiary  under
the federal bankruptcy laws as now or hereafter in effect;

          (i) (1) any member of the Controlled Group shall fail to pay when due,
after the expiration of any applicable  grace period,  any  installment  payment
with respect to its withdrawal  liability  under a  Multiemployer  Plan; (2) any





                                       52




member  of  the  Controlled   Group  shall  fail  to  satisfy  its  contribution
requirements  under Section 412(c)(11) of the Code, whether or not it has sought
a waiver  under  Section  412(d) of the Code;  (3) in the case of an ERISA Event
involving the withdrawal from a Plan of a "substantial  employer" (as defined in
Section  4001(a)(2) or Section  4062(e) of ERISA),  the  withdrawing  employer's
proportionate  share of that Plan's  Unfunded  Pension  Liabilities is more than
$5,000,000  or 10% of its net  worth,  if  greater;  (4) in the case of an ERISA
Event involving the complete or partial  withdrawal  from a Multiemployer  Plan,
the  withdrawing  employer has  incurred a withdrawal  liability in an aggregate
amount exceeding $5,000,000 or 10% of its net worth, if greater; (5) in the case
of an ERISA  Event not  described  in clause (3) or (4),  the  Unfunded  Pension
Liabilities  of the relevant  Plan or Plans exceed  $5,000,000 or 10% of its net
worth,  if greater;  (6) a Plan that is intended to be qualified  under  Section
401(a) of the Code shall lose its qualification,  and the loss can reasonably be
expected  to  impose  on any  member  of the  Controlled  Group  liability  (for
additional taxes, to Plan participants, or otherwise) in the aggregate amount of
$5,000,000 or 10% of its net worth, if greater or more; (7) the  commencement or
increase of  contributions  to, the adoption of, or the  amendment of a Plan by,
any member of the  Controlled  Group shall  result in a net increase in unfunded
liabilities to the Borrower or an ERISA Affiliate in excess of $5,000,000 or 10%
of net worth,  if greater;  or (8) the  occurrence of any  combination of events
listed in clauses  (3)  through (7) that  involves a net  increase in  aggregate
Unfunded Pension Liabilities and unfunded liabilities in excess of $5,000,000 or
10% of its net worth, if greater;

          (j) one or more final  judgments,  orders or decrees  shall be entered
against  the  Borrower  or any member of the  Borrower  Group  involving  in the
aggregate  a  liability  (not  fully  covered by  insurance  and as to which the
insurer has not acknowledged liability) more than an amount equal to the greater
of (i) $5,000,000  and (ii) 10% of the Borrower's net worth,  and the same shall
remain unvacated, undischarged, unstayed or unbonded pending appeal for a period
of 60 days after the entry thereof; or

          (k) any  non-monetary  judgment,  order or  decree  shall be  rendered
against  the  Borrower or any of its  Subsidiaries  which  could  reasonably  be
expected to have a Material Adverse Effect,  and enforcement  proceedings  shall
have been commenced by any Person upon such judgment or order which shall remain
unstayed for any period of 10 consecutive days or more; or

          (l) (i) any provision of the Security and Pledge  Agreement  shall for
any reason cease to be valid and binding on or enforceable against the Borrower,
if the effect  thereof  may  materially  deprive the Banks and the Agents of the
benefits of the Collateral  covered  thereby,  or the Borrower shall so state in
writing or bring an action to limit its  obligations or liabilities  thereunder;





                                       53




(ii) the Security and Pledge Agreement shall for any reason (other than pursuant
to, or  contemplated  by, the terms  thereof)  cease to create a valid  security
interest in the  Collateral  purported  to be covered  thereby or such  security
interest  shall for any reason cease to be a perfected and (except for Permitted
Liens arising by operation of law) first priority security  interest;  (iii) any
of the  outstanding  Obligations of the Borrower  hereunder shall not be Secured
Obligations  (as defined in the  Security and Pledge  Agreement);  or (iv) there
shall occur an event of loss which, together with all other events of loss since
the Effective  Date,  results in a reduction in the value (as  determined in the
reasonable opinion of the Required Banks) of the Collateral of $2,500,000 net of
any cash proceeds received by the Borrower in respect of such event or events of
loss; or

          (m) the FCC or any other  Governmental  Authority shall revoke or fail
to renew any FCC License or any other material  license,  permit or franchise of
the Borrower or any of its  Subsidiaries;  the Borrower or any Subsidiary  shall
for any reason lose any FCC  License or any other  material  license,  permit or
franchise;  or the Borrower or any Subsidiary shall suffer the imposition of any
restraining order, escrow, suspension or impound of funds in connection with any
proceeding  (judicial or administrative)  with respect to any FCC License or any
other material license, permit or franchise;

          (n) there shall occur and be continuing a Material Adverse Effect;

          (o) the Borrower  shall breach or default  under any Rate  Contract to
which any Bank is a party,  if the effect of such  breach or default is to allow
the Bank to  proceed  against  the  Borrower  to  satisfy  any claim of the Bank
against the Borrower in respect of such Rate Contract;

          (p)   there shall occur a Change in Control;

          (q) any Shareholder  Guarantor (other than Baron Capital,  so long as,
with respect to any failure to make a payment described in clause (ii) below, an
amount equal to such payment is paid under the Baron  Capital  Letter of Credit)
shall fail to make any payment (i) in respect of any  Indebtedness or Contingent
Obligation having an aggregate principal or face amount of more than $75,000,000
or (ii) under its Shareholder  Guaranty when due (whether by scheduled maturity,
required  prepayment,  acceleration,  demand  or  otherwise)  and  such  failure
continues after the applicable grace period or notice period, if any,  specified
in the document relating thereto;

          (r)  any  event  or  condition   shall  occur  which  results  in  the
acceleration of the maturity of any Indebtedness or Contingent Obligation of any
Shareholder  Guarantor (other than Baron Capital) having an aggregate  principal





                                       54




or  face  amount  of  more  than  $75,000,000  or  enables  the  holder  of such
Indebtedness  or  Contingent  Obligation  or any Person  acting on such holder's
behalf to accelerate the maturity thereof;

          (s) any  Shareholder  Guaranty or the Baron  Capital  Letter of Credit
shall for any reason be revoked or invalidated or otherwise  cease to be in full
force and  effect  (other  than in  accordance  with its terms as the  result of
performance  in  full  of  the  relevant  Shareholder   Guarantor's  obligations
thereunder)  or any  Shareholder  Guarantor  (other than Baron Capital) shall so
assert in writing or any  Shareholder  Guarantor  shall bring an action to limit
its liabilities thereunder;

          (t) Hughes' senior unsecured long-term securities (without third-party
credit  enhancement)  shall not be rated  Baa3 or above by  Moody's  and BBB- or
above by S&P; or

          (u) Hughes and either other Shareholder  Guarantor shall have notified
any of the  Agents  and  the  banks  of the  existence  of a  Guaranty  Issuance
Agreement Event of Default;

then, and in every such event, the  Administrative  Agent shall (i) if requested
by Banks having more than 50% in aggregate amount of the Commitments,  by notice
to the Borrower  terminate the Commitments  and they shall thereupon  terminate,
and (ii) if requested by Banks holding more than 50% of the aggregate  principal
amount of the Loans, by notice to the Borrower  declare the Loans (together with
accrued  interest  thereon)  to  be,  and  the  Loans  shall  thereupon  become,
immediately due and payable without presentment, demand, protest or other notice
of any kind,  all of which are hereby waived by the  Borrower;  provided that in
the case of any of the  Events of Default  specified  in clause (g) or (h) above
with  respect to the  Borrower,  without any notice to the Borrower or any other
act by the  Administrative  Agent or the Banks, the Commitments  shall thereupon
terminate and the Loans  (together with accrued  interest  thereon) shall become
immediately due and payable without presentment, demand, protest or other notice
of any kind,  all of which are  hereby  waived by the  Borrower.  If any  amount
payable under this Agreement shall not be paid when due, then the Administrative
Agent  shall,  if  requested  by Banks  holding  more than 50% of the  aggregate
principal  amount  (excluding any Loans held by the Borrower or any  Shareholder
Guarantor or any Affiliate of the  foregoing) of the Tranche A Loans,  Tranche B
Loans or Tranche C Loans, as the case may be, demand payment  therefor under the
relevant Shareholder Guaranty.

         SECTION 6.02. Notice of Default.  The  Administrative  Agent shall give
notice to the Borrower under Section 6.01(c) promptly upon being requested to do
so by any Bank and shall thereupon notify all the Banks thereof.




                                       55





                                    ARTICLE 7
                                   THE AGENTS

         SECTION 7.01.  Appointment  and  Authorization.  Each Bank  irrevocably
appoints  and  authorizes  each Agent to take such action as agent on its behalf
and to exercise such powers under this Agreement,  the Notes and each other Loan
Document as are delegated to such Agent by the terms hereof or thereof, together
with all such powers as are reasonably incidental thereto.

         SECTION 7.02.  Agents and Affiliates.  Morgan Guaranty Trust Company of
New York shall have the same rights and powers under this Agreement as any other
Bank and may exercise or refrain from  exercising the same as though it were not
an Agent, and each of Toronto Dominion  (Texas),  Inc. and Morgan Guaranty Trust
Company of New York and its affiliates may accept  deposits from, lend money to,
and generally engage in any kind of business with the Borrower or any Subsidiary
or affiliate of the Borrower as if it were not an Agent.

         SECTION 7.03. Action by Agents. The obligations of the Agents hereunder
are only those  expressly set forth herein.  Without  limiting the generality of
the foregoing,  the Agents shall not be required to take any action with respect
to any Default, except as expressly provided in Article 6.

         SECTION 7.04.  Consultation with Experts. Either Agent may consult with
legal  counsel  (who  may be  counsel  for  the  Borrower),  independent  public
accountants  and other  experts  selected  by it and shall not be liable for any
action taken or omitted to be taken by it in good faith in  accordance  with the
advice of such counsel, accountants or experts.

         SECTION 7.05. Liability of Agents. No Agent or any of its affiliates or
any of their respective directors, officers, agents or employees shall be liable
for any  action  taken or not taken by it in  connection  herewith  (i) with the
consent or at the  request of the  Required  Banks or (ii) in the absence of its
own gross negligence or willful misconduct. No Agent or any of its affiliates or
any of their  respective  directors,  officers,  agents  or  employees  shall be
responsible  for or have any duty to  ascertain,  inquire into or verify (i) any
statement,  warranty or representation made in connection with this Agreement or
the  Borrowing  hereunder;  (ii) the  performance  or  observance  of any of the
covenants or agreements of the Borrower; (iii) the satisfaction of any condition
specified in Article 3, except  receipt of items required to be delivered to the
Documentation Agent; or (iv) the validity,  effectiveness or genuineness of this
Agreement,  the Notes or any other instrument or writing furnished in connection
herewith.  No Agent shall  incur any  liability  by acting in reliance  upon any





                                       56




notice, consent,  certificate,  statement, or other writing (which may be a bank
wire,  telex,  facsimile  transmission or similar writing)  believed by it to be
genuine or to be signed by the proper party or parties.

         SECTION 7.06.  Indemnification.  Each Bank shall, ratably in accordance
with its Commitment,  indemnify each Agent,  its affiliates and their respective
directors,  officers,  agents and employees (to the extent not reimbursed by the
Borrower) against any cost, expense (including counsel fees and  disbursements),
claim,  demand,  action,  loss or  liability  (except  such as result  from such
indemnitee's  gross  negligence or willful  misconduct) that such indemnitee may
suffer or incur in connection with this Agreement or any action taken or omitted
by such indemnitee hereunder.

         SECTION 7.07.  Credit  Decision.  Each Bank  acknowledges  that it has,
independently  and without  reliance  upon either  Agent or any other Bank,  and
based on such documents and information as it has deemed  appropriate,  made its
own credit  analysis and decision to enter into this  Agreement.  Each Bank also
acknowledges that it will,  independently and without reliance upon either Agent
or any other Bank, and based on such documents and  information as it shall deem
appropriate at the time,  continue to make its own credit decisions in taking or
not taking any action under this Agreement.

         SECTION 7.08.  Successor Agent.  Either Agent may resign at any time by
giving notice thereof to the Banks and the Borrower.  Upon any such resignation,
the  Required  Banks  shall have the right to appoint a successor  Agent.  If no
successor  Agent shall have been so appointed by the Required  Banks,  and shall
have accepted such  appointment,  within 30 days after the retiring  Agent gives
notice of  resignation,  then the  retiring  Agent may,  on behalf of the Banks,
appoint a  successor  Agent,  which  shall be a  commercial  bank  organized  or
licensed  under the laws of the United States of America or of any State thereof
and having a combined  capital  and  surplus of at least  $50,000,000.  Upon the
acceptance of its  appointment  as Agent  hereunder by a successor  Agent,  such
successor Agent shall thereupon succeed to and become vested with all the rights
and duties of the retiring  Agent,  and the retiring  Agent shall be  discharged
from  its  duties  and  obligations   hereunder.   After  any  retiring  Agent's
resignation  hereunder as Agent,  the  provisions of this Article shall inure to
its  benefit as to any  actions  taken or omitted to be taken by it while it was
Agent.

         SECTION 7.09.  Agents' Fees.  The Borrower  shall pay to each Agent for
its own  account  fees in the amounts  and at the times  previously  agreed upon
between the Borrower and such Agent.






                                       57





                                    ARTICLE 8
                             CHANGE IN CIRCUMSTANCES

          SECTION  8.01.  Basis for  Determining  Interest  Rate  Inadequate  or
Unfair.  If on or  prior  to the  first  day  of any  Interest  Period  for  any
Euro-Dollar Loan:

          (a) the  Administrative  Agent is advised by the Reference  Banks that
deposits in dollars (in the  applicable  amounts)  are not being  offered to the
Reference Banks in the London interbank market for such Interest Period, or

          (b) Banks having 50% or more of the aggregate  principal amount of the
affected  Loans  advise  the  Administrative  Agent  that  the  Adjusted  London
Interbank  Offered  Rate as  determined  by the  Administrative  Agent  will not
adequately  and  fairly  reflect  the  cost  to  such  Banks  of  funding  their
Euro-Dollar Loans for such Interest Period,

the Administrative Agent shall forthwith give notice thereof to the Borrower and
the Banks,  whereupon until the Administrative  Agent notifies the Borrower that
the  circumstances  giving  rise to such  suspension  no longer  exist,  (i) the
obligations  of the Banks to make  Euro-Dollar  Loans or to  continue or convert
outstanding  Loans as or into Euro-Dollar Loans shall be suspended and (ii) each
outstanding  Euro-Dollar  Loan shall be  converted  into a Base Rate Loan on the
last day of the then current  Interest  Period  applicable  thereto.  Unless the
Borrower notifies the  Administrative  Agent at least two Domestic Business Days
before the date of the Borrowing,  if it is to be a Euro-Dollar  Borrowing,  for
which the Notice of Borrowing  has  previously  been given that it elects not to
borrow  on such  date,  the  Borrowing  shall  instead  be  made as a Base  Rate
Borrowing.  The  Administrative  Agent  shall  notify  the  Borrower  as soon as
reasonably  possible upon learning  that the  circumstances  giving rise to such
suspension no longer exist.

         SECTION 8.02.  Illegality.  If, on or after the date of this Agreement,
the adoption of any  applicable  law, rule or  regulation,  or any change in any
applicable  law,  rule or  regulation,  or any change in the  interpretation  or
administration thereof by any governmental authority, central bank or comparable
agency charged with the interpretation or administration  thereof, or compliance
by any Bank (or its  Euro-Dollar  Lending  Office) with any request or directive
(whether or not having the force of law) of any such authority,  central bank or
comparable  agency  shall make it  unlawful or  impossible  for any Bank (or its
Euro-Dollar  Lending Office) to make, maintain or fund its Euro-Dollar Loans and
such Bank shall so notify the  Administrative  Agent, the  Administrative  Agent
shall  forthwith  give  notice  thereof  to the other  Banks  and the  Borrower,





                                       58




whereupon  until such Bank  notifies the Borrower and the  Administrative  Agent
that the  circumstances  giving rise to such  suspension  no longer  exist,  the
obligation of such Bank to make  Euro-Dollar  Loans,  or to convert  outstanding
Loans into Euro-Dollar  Loans,  shall be suspended.  Before giving any notice to
the Administrative  Agent pursuant to this Section,  such Bank shall designate a
different Euro-Dollar Lending Office if such designation will avoid the need for
giving  such notice and will not, in the  judgment  of such Bank,  be  otherwise
disadvantageous  to such Bank. If such notice is given, each Euro-Dollar Loan of
such Bank then outstanding  shall be converted to a Base Rate Loan either (a) on
the last day of the then current Interest Period  applicable to such Euro-Dollar
Loan if such Bank may  lawfully  continue to maintain and fund such Loan to such
day or (b)  immediately  if such Bank shall  determine  that it may not lawfully
continue to maintain and fund such Loan to such day.  Each Bank shall notify the
Administrative  Agent and the Borrower as soon as reasonably  possible after the
circumstances  giving  rise to any  suspension  by such Bank  described  in this
Section 8.02 no longer exist.

         SECTION 8.03. Increased Cost and Reduced Return. (a) If on or after the
date hereof,  the adoption of any  applicable  law, rule or  regulation,  or any
change  in  any  applicable  law,  rule  or  regulation,  or any  change  in the
interpretation or administration thereof by any governmental authority,  central
bank or comparable  agency  charged with the  interpretation  or  administration
thereof,  or compliance by any Bank (or its Applicable  Lending Office) with any
request  or  directive  (whether  or not  having  the  force of law) of any such
authority,  central  bank or  comparable  agency  shall  impose,  modify or deem
applicable any reserve  (including,  without  limitation,  any such  requirement
imposed by the Board of Governors of the Federal Reserve  System,  but excluding
any such requirement included in an applicable  Euro-Dollar Reserve Percentage),
special deposit,  insurance assessment or similar requirement against assets of,
deposits  with or for the  account of, or credit  extended  by, any Bank (or its
Applicable  Lending  Office)  or shall  impose  on any  Bank (or its  Applicable
Lending Office) or the London interbank market any other condition affecting its
Euro-Dollar  Loans, its Note or its obligation to make Euro-Dollar Loans and the
result  of any of the  foregoing  is to  increase  the cost to such Bank (or its
Applicable  Lending Office) of making or maintaining any Euro-Dollar Loan, or to
reduce  the  amount  of any sum  received  or  receivable  by such  Bank (or its
Applicable  Lending  Office) under this Agreement or under its Note with respect
thereto,  by an amount deemed by such Bank to be material,  then, within 15 days
after  demand  by  such  Bank  (with a copy to the  Administrative  Agent),  the
Borrower  shall pay to such  Bank such  additional  amount  or  amounts  as will
compensate  such Bank for such increased cost or reduction;  provided,  however,
that in the case of an increase  referred to above  resulting from the published
interpretation by a governmental authority,  such Bank shall be entitled to make
demand  on  the  Borrower  in  respect  thereof  only  within  180  days  of the
publication of such interpretation.




                                       59





          (b) If any Bank shall have determined that, after the date hereof, the
adoption of any applicable law, rule or regulation  regarding  capital adequacy,
or any  change  in any  such  law,  rule or  regulation,  or any  change  in the
interpretation or administration thereof by any governmental authority,  central
bank or comparable  agency  charged with the  interpretation  or  administration
thereof,  or any request or directive regarding capital adequacy (whether or not
having  the  force of law) of any such  authority,  central  bank or  comparable
agency,  has or would have the effect of reducing  the rate of return on capital
of such  Bank  (or its  Parent)  as a  consequence  of such  Bank's  obligations
hereunder  to a level  below  that which  such Bank (or its  Parent)  could have
achieved  but for such  adoption,  change,  request or  directive  (taking  into
consideration its policies with respect to capital adequacy) by an amount deemed
by such Bank to be material, then from time to time, within 15 days after demand
by such Bank (with a copy to the  Administrative  Agent), the Borrower shall pay
to such Bank such additional  amount or amounts as will compensate such Bank (or
its  Parent)  for  such  reduction;  provided,  however,  that in the case of an
increase  referred to above  resulting  from the published  interpretation  by a
governmental  authority,  such  Bank  shall be  entitled  to make  demand on the
Borrower  in respect  thereof  only within 180 days of the  publication  of such
interpretation.

          (c) Each Bank will promptly notify the Borrower and the Administrative
Agent of any event of which it has knowledge,  occurring  after the date hereof,
which will entitle such Bank to  compensation  pursuant to this Section and will
designate a different  Lending  Office if such  designation  will avoid the need
for, or reduce the amount of, such compensation and will not, in the judgment of
such Bank, be otherwise  disadvantageous to such Bank. A certificate of any Bank
claiming compensation under this Section and setting forth the additional amount
or amounts to be paid to it  hereunder  shall be  conclusive  in the  absence of
manifest  error.  In determining  such amount,  such Bank may use any reasonable
averaging  and  attribution  methods.  Each Bank will notify the  Administrative
Agent and the Borrower as soon as  reasonably  possible  after any  circumstance
entitling such Bank to  compensation  pursuant to this Section 8.03(c) no longer
exists.

         SECTION 8.04.  Taxes.  (a) For the purposes of this Section 8.04 , the
following terms have the following meanings:

         "Taxes"  means any and all  present or future  taxes,  duties,  levies,
imposts, deductions,  charges or withholdings with respect to any payment by the
Borrower,  as the case may be, pursuant to this Agreement or under any Note, and
all liabilities with respect thereto, excluding (i) in the case of each Bank and
Agent,  taxes  imposed on its income,  and franchise or similar taxes imposed on
it, by a  jurisdiction  under the laws of which  such Bank or Agent (as the case





                                       60




may be) is organized or in which its principal  executive  office is located or,
in the case of each Bank, in which its Applicable  Lending Office is located and
(ii) in the case of each Bank, any United States withholding tax imposed on such
payments  but only to the  extent  that such Bank is  subject  to United  States
withholding tax at the time such Bank first becomes a party to this Agreement.

         "Other  Taxes" means any present or future stamp or  documentary  taxes
and any other  excise or property  taxes,  or similar  charges or levies,  which
arise from any payment made pursuant to this Agreement or under any Note or from
the  execution or delivery of, or otherwise  with respect to, this  Agreement or
any Note.

          (b) Any and all  payments by the Borrower to or for the account of any
Bank or Agent  hereunder or under any Note shall be made without  deduction  for
any Taxes or Other Taxes;  provided  that, if the Borrower  shall be required by
law to  deduct  any Taxes or Other  Taxes  from any such  payments,  (i) the sum
payable  shall be  increased  as  necessary  so that after  making all  required
deductions  (including  deductions  applicable to additional  sums payable under
this  Section)  such Bank or Agent (as the case may be) receives an amount equal
to the sum it would have  received had no such  deductions  been made,  (ii) the
Borrower  shall  make such  deductions,  (iii) the  Borrower  shall pay the full
amount  deducted  to the  relevant  taxation  authority  or other  authority  in
accordance  with  applicable  law and (iv) the  Borrower  shall  furnish  to the
Administrative  Agent, at its address referred to in Section 9.01 , the original
or a certified copy of a receipt evidencing payment thereof.

          (c) The Borrower  agrees to indemnify each Bank and Agent for the full
amount of Taxes or Other  Taxes  (including,  without  limitation,  any Taxes or
Other Taxes  imposed or asserted by any  jurisdiction  on amounts  payable under
this  Section) paid by such Bank or Agent (as the case may be) and any liability
(including penalties, interest and expenses, other than those resulting from any
act or failure to act by such Bank) arising  therefrom or with respect  thereto.
This  indemnification  shall be paid within 15 days after such Bank or Agent (as
the case may be) makes demand therefor.

          (d) Each Bank organized  under the laws of a jurisdiction  outside the
United  States,  on or prior to the date of its  execution  and delivery of this
Agreement in the case of each Bank listed on the  signature  pages hereof and on
or prior to the date on which it becomes a Bank in the case of each other  Bank,
and from time to time  thereafter  if requested in writing by the Borrower  (but
only so long as such Bank remains  lawfully  able to do so),  shall  provide the
Borrower and the Administrative Agent with Internal Revenue Service form 1001 or
4224, as appropriate,  or any successor form prescribed by the Internal  Revenue
Service,  certifying  that such Bank is entitled to benefits under an income tax
treaty to which the United  States is a party which exempts the Bank from United





                                       61




States  withholding  tax or reduces the rate of  withholding  tax on payments of
interest for the account of such Bank or certifying  that the income  receivable
pursuant to this Agreement is effectively  connected with the conduct of a trade
or business in the United States.

          (e) For any period with  respect to which a Bank has failed to provide
the Borrower or the  Administrative  Agent with the appropriate form pursuant to
Section  8.04(d)  (unless  such  failure  is due to a change in  treaty,  law or
regulation  occurring  subsequent to the date on which such form  originally was
required to be  provided),  such Bank shall not be  entitled to  indemnification
under  Section  8.04(b) or 8.04(c) with  respect to Taxes  imposed by the United
States;  provided that if a Bank, which is otherwise exempt from or subject to a
reduced rate of withholding tax, becomes subject to Taxes because of its failure
to deliver a form required hereunder, the Borrower shall take such steps as such
Bank shall reasonably request to assist such Bank to recover such Taxes.

          (f) If the  Borrower is required to pay  additional  amounts to or for
the account of any Bank pursuant to this Section, then such Bank will change the
jurisdiction of its Applicable  Lending Office if, in the judgment of such Bank,
such change (i) will eliminate or reduce any such  additional  payment which may
thereafter accrue and (ii) is not otherwise disadvantageous to such Bank.

         SECTION  8.05.  Base Rate Loans  Substituted  for Affected  Euro-Dollar
Loans. If (i) the obligation of any Bank to make, or convert  outstanding  Loans
to,  Euro-Dollar  Loans has been suspended  pursuant to Section 8.02 or (ii) any
Bank has demanded  compensation  under  Section 8.03 or 8.04 with respect to its
Euro-Dollar Loans and the Borrower shall, by at least five Euro-Dollar  Business
Days' prior notice to such Bank through the  Administrative  Agent, have elected
that the provisions of this Section shall apply to such Bank,  then,  unless and
until such Bank notifies the Borrower that the circumstances giving rise to such
suspension or demand for compensation no longer exist:

          (a) all  Loans  which  would  otherwise  be  made by such  Bank as (or
continued as or converted  into)  Euro-Dollar  Loans shall  instead be Base Rate
Loans (on which interest and principal shall be payable  contemporaneously  with
the related Euro-Dollar Loans of the other Banks); and

          (b) after each of its Euro-Dollar  Loans has been repaid (or converted
to a Base Rate Loan), all payments of principal which would otherwise be applied
to repay such  Euro-Dollar  Loans  shall be applied to repay its Base Rate Loans
instead.





                                       62





If such Bank  notifies the Borrower that the  circumstances  giving rise to such
notice no longer apply,  the principal  amount of each such Base Rate Loan shall
be converted  into a  Euro-Dollar  Loan on the first day of the next  succeeding
Interest Period applicable to the related Euro-Dollar Loans of the other Banks.



                                    ARTICLE 9
                                  MISCELLANEOUS

         SECTION 9.01. Notices.  All notices,  requests and other communications
to any party  hereunder  shall be in writing  (including  bank  wire,  facsimile
transmission  or similar  writing) and shall be given to such party:  (a) in the
case of the Borrower or either  Agent,  at its address or  facsimile  number set
forth on the signature pages hereof, (b) in the case of any Bank, at its address
or facsimile number set forth in its Administrative  Questionnaire or (c) in the
case of any party,  such other  address  or  facsimile  number as such party may
hereafter specify for the purpose by notice to the Agents and the Borrower. Each
such notice,  request or other  communication shall be effective (i) if given by
facsimile  transmission,  when  transmitted to the facsimile number specified in
this Section and confirmation of receipt is received,  (ii) if given by mail, 72
hours  after such  communication  is  deposited  in the mails  with first  class
postage  prepaid,  addressed  as aforesaid or (iii) if given by any other means,
when delivered at the address  specified in this Section;  provided that notices
to the Administrative  Agent under Article 2 or Article 8 shall not be effective
until received.

         SECTION  9.02.  No Waivers.  No failure or delay by either Agent or any
Bank in  exercising  any right,  power or privilege  hereunder or under any Note
shall  operate as a waiver  thereof  nor shall any  single or  partial  exercise
thereof  preclude any other or further  exercise  thereof or the exercise of any
other right,  power or privilege.  The rights and remedies herein provided shall
be cumulative and not exclusive of any rights or remedies provided by law.

         SECTION 9.03. Expenses; Indemnification. (a) The Borrower shall pay (i)
all  out-of-pocket  expenses  of  the  Agents,  including  reasonable  fees  and
disbursements  of  special  counsel  for the  Agents,  in  connection  with  the
preparation  and  administration  of  this  Agreement,  any  waiver  or  consent
hereunder or any amendment  hereof or any Default or alleged  Default  hereunder
and (ii) if an Event of Default occurs,  all out-of-pocket  expenses incurred by
each Agent and Bank, including (without  duplication) the fees and disbursements
of outside counsel and the allocated cost of inside counsel,  in connection with
such  Event  of  Default  and  collection,   bankruptcy,  insolvency  and  other
enforcement proceedings resulting therefrom.




                                       63





          (b) The  Borrower  agrees to  indemnify  each  Agent  and Bank,  their
respective  affiliates  and  the  respective  directors,  officers,  agents  and
employees  of the  foregoing  (each an  "Indemnitee")  and hold each  Indemnitee
harmless from and against any and all liabilities,  losses,  damages,  costs and
expenses of any kind,  including,  without  limitation,  the reasonable fees and
disbursements of counsel, which may be incurred by such Indemnitee in connection
with any investigative,  administrative or judicial  proceeding  (whether or not
such  Indemnitee  shall be  designated a party  thereto)  brought or  threatened
relating to or arising out of this  Agreement  or any actual or proposed  use of
proceeds of Loans hereunder; provided that no Indemnitee shall have the right to
be indemnified  hereunder for such  Indemnitee's own gross negligence or willful
misconduct as determined by a court of competent jurisdiction.

         SECTION 9.04.  Sharing of Set-offs.  Each Bank agrees that if it shall,
by exercising any right of set-off or counterclaim or otherwise  (other than any
such right against a Shareholder Guarantor),  receive payment of a proportion of
the aggregate amount of principal and interest due with respect to any Note held
by it which is greater than the proportion received by any other Bank in respect
of the  aggregate  amount of principal and interest due with respect to any Note
held by such other Bank, the Bank receiving such proportionately greater payment
shall  purchase such  participations  in the Notes held by the other Banks,  and
such  other  adjustments  shall be  made,  as may be  required  so that all such
payments of principal  and interest  with respect to the Notes held by the Banks
shall be shared by the Banks pro rata;  provided  that  nothing in this  Section
shall  impair  the  right of any  Bank to  exercise  any  right  of  set-off  or
counterclaim it may have and to apply the amount subject to such exercise to the
payment of indebtedness of the Borrower other than its  indebtedness  hereunder.
The  Borrower  agrees,  to the  fullest  extent it may  effectively  do so under
applicable  law, that any holder of a  participation  in a Note,  whether or not
acquired pursuant to the foregoing arrangements,  may exercise rights of set-off
or counterclaim and other rights with respect to such  participation as fully as
if such holder of a participation  were a direct creditor of the Borrower in the
amount of such participation.

         SECTION 9.05.  Amendments and Waivers.  Any provision of this Agreement
or the Notes may be amended or waived if, but only if, such  amendment or waiver
is in writing and is signed by the Borrower and the Required  Banks (and, if the
rights or duties of an Agent are affected thereby, by such Agent); provided that
no such amendment or waiver shall,  unless signed by all the Banks, (a) increase
or decrease the  Commitment  of any Bank  (except for a ratable  decrease in the
Commitments of all Banks) or subject any Bank to any additional obligation,  (b)
reduce the principal of or rate of interest on any Loan, or any fees  hereunder,
(c)  postpone  the date fixed for any payment of principal of or interest on any
Loan, or any fees hereunder or for any scheduled reduction or termination of any





                                       64




Commitment,  (d) release the  Borrower  from its  obligations  hereunder  or the
Shareholder Guarantors from their obligations under the Shareholders Guaranties,
(e)  release  all or  substantially  all of the  Collateral,  or (f)  change the
percentage of the Commitments or of the aggregate unpaid principal amount of the
Notes,  or the number of Banks,  which shall be required for the Banks or any of
them to take any  action  under  this  Section  or any other  provision  of this
Agreement.

         SECTION  9.06.  Successors  and  Assigns.  (a) The  provisions  of this
Agreement  shall be binding upon and inure to the benefit of the parties  hereto
and their  respective  successors and assigns,  except that the Borrower may not
assign or otherwise  transfer any of its rights under this Agreement without the
prior written consent of all Banks.

          (b) Any  Bank  may at any  time  grant  to one or more  banks or other
institutions (each a "Participant") participating interests in its Commitment or
any or all of  its  Loans.  In the  event  of  any  such  grant  by a Bank  of a
participating  interest  to a  Participant,  whether  or not upon  notice to the
Borrower and the Agents,  such Bank shall remain responsible for the performance
of its obligations hereunder,  and the Borrower and the Agents shall continue to
deal solely and directly  with such Bank in  connection  with such Bank's rights
and obligations under this Agreement.  Any agreement  pursuant to which any Bank
may grant  such a  participating  interest  shall  provide  that such Bank shall
retain  the sole right and  responsibility  to enforce  the  obligations  of the
Borrower  hereunder  including,  without  limitation,  the right to approve  any
amendment,  modification or waiver of any provision of this Agreement;  provided
that such  participation  agreement may provide that such Bank will not agree to
any modification, amendment or waiver of this Agreement described in clause (a),
(b),  (c),  (d) or (e) of the proviso to Section 9.05 without the consent of the
Participant.  The Borrower  agrees that each  Participant  shall,  to the extent
provided in its participation  agreement, be entitled to the benefits of Article
8 with respect to its  participating  interest.  An assignment or other transfer
which is not permitted by subsection  (c) or (d) below shall be given effect for
purposes  of this  Agreement  only to the  extent  of a  participating  interest
granted in accordance with this subsection (b).

          (c) Any Bank may at any time,  upon five Business Days' written notice
to each of the Agents,  assign to one or more banks or other  institutions (each
an "Assignee") all, or a proportionate part (equivalent to an initial Commitment
of not less than  $2,500,000) of all, of its rights and  obligations  under this
Agreement  and the  Notes,  and such  Assignee  shall  assume  such  rights  and
obligations, pursuant to an Assignment and Assumption Agreement in substantially
the form of Exhibit D hereto executed by such Assignee and such transferor Bank,
with  (and  subject  to)  the  subscribed   consent  of  the  Borrower  and  the
Administrative  Agent,  which  consent  shall in each  case not be  unreasonably
withheld;  provided  that (x) if an Assignee is an affiliate of such  transferor
Bank or was a Bank immediately prior to such assignment or




                                       65





if the Assignee is a Shareholder  Guarantor purchasing Notes pursuant to Section
1(e) of a Shareholder  Guaranty,  no such consent shall be required and (y) such
Bank shall contemporaneously assign to such Assignee an equivalent percentage of
loans under the Revolving Credit Agreement.  Upon execution and delivery of such
instrument  and payment by such  Assignee to such  transferor  Bank of an amount
equal  to the  purchase  price  agreed  between  such  transferor  Bank and such
Assignee,  such Assignee  shall be a Bank party to this Agreement and shall have
all the rights and  obligations of a Bank with a Commitment as set forth in such
instrument of  assumption,  and the  transferor  Bank shall be released from its
obligations  hereunder  to a  corresponding  extent,  and no further  consent or
action by any party shall be required.  Upon the  consummation of any assignment
pursuant to this subsection (c), the transferor Bank, the  Administrative  Agent
and the Borrower shall make appropriate arrangements so that, if required, a new
Note is issued to the Assignee,  and the  transferor  Bank shall provide  prompt
written notice of such assignment to the Documentation Agent. In connection with
any such assignment,  the transferor Bank shall pay to the Administrative  Agent
an administrative fee for processing such assignment in the amount of $2,500. If
the Assignee is not incorporated  under the laws of the United States of America
or a state  thereof,  it shall  deliver to the Borrower  and the  Administrative
Agent  certification as to exemption from deduction or withholding of any United
States federal income taxes in accordance with Section 8.04.

          (d) Any Bank may at any time  assign all or any  portion of its rights
under this Agreement and its Note to a Federal  Reserve Bank. No such assignment
shall release the transferor Bank from its obligations hereunder.

          (e) No Assignee,  Participant or other transferee of any Bank's rights
shall be entitled to receive any greater payment under Section 8.03 or 8.04 than
such Bank  would  have been  entitled  to  receive  with  respect  to the rights
transferred,  unless such  transfer is made with the  Borrower's  prior  written
consent or by reason of the  provisions of Section 8.02,  8.03 or 8.04 requiring
such Bank to  designate a different  Applicable  Lending  Office  under  certain
circumstances  or at a time when the  circumstances  giving rise to such greater
payment did not exist.

          (f) Each Bank shall,  upon receipt from a Shareholder  Guarantor of an
amount  equal to all of such Bank's  Guaranteed  Obligations  (as defined in the
relevant  Shareholder  Guaranty)  (the  "Transfer  Payment"),   assign  to  such
Shareholder  Guarantor the  corresponding  portion of its rights and obligations
under this  Agreement  and the Notes in  accordance  with  paragraph (c) of this
Section   9.06;   provided  that  (i)  the  consent  of  the  Borrower  and  the
Administrative  Agent shall not be required for such assignment and (ii) no such
assignment  shall be effective until each Bank has received its Transfer Payment
from the applicable Shareholder Guarantor.




                                       66






          SECTION 9.07.  Collateral.  Each of the Banks represents to the Agents
and  each of the  other  Banks  that it in good  faith is not  relying  upon any
"margin  stock" (as defined in  Regulation  U) as collateral in the extension or
maintenance of the credit provided for in this Agreement.

         SECTION 9.08. Governing Law; Submission to Jurisdiction. This Agreement
and each Note shall be governed by and construed in accordance  with the laws of
the  State  of New  York.  The  Borrower  hereby  submits  to  the  nonexclusive
jurisdiction  of the United States  District Court for the Southern  District of
New York and of any New York State court  sitting in New York City for  purposes
of all legal  proceedings  arising out of or relating to this  Agreement  or the
transactions  contemplated  hereby.  The  Borrower  irrevocably  waives,  to the
fullest  extent  permitted by law, any  objection  which it may now or hereafter
have to the laying of the venue of any such  proceeding  brought in such a court
and any claim that any such proceeding  brought in such a court has been brought
in an inconvenient forum.

         SECTION 9.09. Counterparts;  Integration; Effectiveness. This Agreement
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.  This Agreement  constitutes the entire agreement and  understanding
among  the  parties  hereto  and  supersedes  any and all prior  agreements  and
understandings,  oral or written,  relating to the subject matter  hereof.  This
Agreement  shall become  effective  upon receipt by the  Documentation  Agent of
counterparts hereof signed by each of the parties hereto (or, in the case of any
party as to which an executed counterpart shall not have been received,  receipt
by the  Documentation  Agent in form  satisfactory to it of telegraphic,  telex,
facsimile  or other  written  confirmation  from such  party of  execution  of a
counterpart hereof by such party).

          SECTION 9.10. Waiver of Jury Trial.  EACH OF THE BORROWER,  THE AGENTS
AND THE BANKS  HEREBY  IRREVOCABLY  WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN
ANY  LEGAL  PROCEEDING  ARISING  OUT OF OR  RELATING  TO THIS  AGREEMENT  OR THE
TRANSACTIONS CONTEMPLATED HEREBY.

         SECTION  9.11.  Confidentiality.  Each Bank  agrees to take  normal and
reasonable  precautions and exercise due care to maintain the confidentiality of
all  non-public  information  provided  to it by  the  Borrower  or  any  of its
Subsidiaries  by the Agents on the  Borrower's  or such  Subsidiary's  behalf in
connection with this Agreement or any other Loan Document and neither it nor any
of its  Affiliates  shall use any such  information  for any  purpose  or in any





                                       67




manner other than pursuant to the terms  contemplated by this Agreement,  except
to the extent such  information  (a) was or becomes  generally  available to the
public other than as a result of a disclosure by the Bank, or (b) was or becomes
available on a  non-confidential  basis from a source  other than the  Borrower,
provided that such source is not bound by a  confidentiality  agreement with the
Borrower known to the Bank; provided,  further,  that any Bank may disclose such
information  (A) to any other Bank or to the  Agents,  (B) at the request of any
regulatory  authority or in connection  with an  examination of such Bank by any
such  authority;  (C)  pursuant to subpoena  or other  court  process;  (D) when
required to do so in accordance  with the provisions of any applicable  law; (E)
at the express  direction of any other agency of any State of the United  States
of  America  or of any  other  jurisdiction  in which  such  Bank  conducts  its
business;  and  (F) to such  Bank's  independent  auditors  and  legal  counsel.
Notwithstanding  the foregoing,  the Company authorizes each Bank to disclose to
any  Participant  or  Assignee  (each,  a  "Transferee")   and  any  prospective
Transferee  such  financial  and other  information  in such  Bank's  possession
concerning the Borrower or any of its  Subsidiaries  which has been delivered to
the Banks pursuant to this Agreement or which has been delivered to the Banks by
the Borrower or any of its  Subsidiaries  in  connection  with the Banks' credit
evaluation  of the Borrower  and its  Subsidiaries  prior to entering  into this
Agreement;  provided that such Transferee agrees in writing to such Bank to keep
such  information  confidential  to  the  same  extent  required  of  the  Banks
hereunder.




                                       68





         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly  executed by their  respective  authorized  officers as of the day and year
first above written.

                             AMERICAN MOBILE SATELLITE
                             CORPORATION


                             By  /s/Gary M. Parsons
                                 ------------------

                             Name:      Gary M. Parsons
                             Title:     President and Chief
                                        Executive Officer
                             Address:   10802 Parkridge Boulevard
                                        Reston, VA 20191
                             Attention: General Counsel
                             Facsimile: 703-758-6134




                                       69





                             TORONTO DOMINION (TEXAS), INC.


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


                             MORGAN GUARANTY TRUST
                             COMPANY OF NEW YORK


                             By   /s/John M. Mikolay
                                  ------------------
                             Name:      John M. Mikolay
                             Title:     Vice President


                             BANK OF AMERICA NATIONAL
                             TRUST AND SAVINGS
                             ASSOCIATION


                             By    /s/Robert W. Troutman
                                   ---------------------
                             Name:      Robert W. Troutman
                             Title:     Managing Director






                                       70





                             MORGAN GUARANTY TRUST
                             COMPANY OF NEW YORK, as
                             Documentation Agent


                             By   /s/John M. Mikolay
                                  ------------------
                             Name:      John M. Mikolay
                             Title:     Vice President
                             Address:   500 Stanton Christiana Road
                                        Newark, DE 19713
                             Attention: Victoria Fedele
                                        Facsimile: 302-634-1852


                             TORONTO DOMINION (TEXAS),
                             INC., as Administrative Agent


                             By  /s/Jano Mott
                                 ------------
                             Name:      Jano Mott      
                             Title:     Vice President
                             Address:   909 Fannin Street
                                        Houston, TX 77010
                             Attention: Jano Mott
                             Facsimile: 713-951-9921




                                       71







                               COMMITMENT SCHEDULE


              Bank               Tranche A        Tranche B        Tranche C
                                 Commitment       Commitment       Commitment
                                                                 
Toronto Dominion (Texas),       $37,500,000               $0       $6,250,000
Inc.
Morgan Guaranty Trust            37,500,000               $0       $6,250,000
Company of New York
Bank of America National                 $0      $12,500,000               $0
Trust and Savings
Association






                                                1





                                PRICING SCHEDULE

         "Euro-Dollar Margin" means for any date the rate set forth below in the
column corresponding to the "Pricing Level" that applies at such date:



                        Level I       Level II         Level III
Euro-Dollar Margin       0.50%          0.75%             1.00%
- -------------------   -----------   -------------     ------------


         For purposes of this Schedule,  the following  terms have the following
meanings:

         "Level I  Pricing"  applies  at any date if, as of such  date,  Hughes'
long-term debt is rated A3 or higher by Moody's and A- or higher by S&P

         "Level II Pricing" applies at any date if, as of such date, (i) Hughes'
long-term  debt is rated Baa2 or higher by Moody's  and BBB or higher by S&P and
(ii) Level I Pricing does not apply.

         "Level III Pricing" applies at any date if neither Level I nor Level II
Pricing applies.

         "Moody's" means Moody's Investors Service, Inc.

         "Pricing Level" refers to the  determination of which of Level I, Level
II or Level III applies at any date.

         "S&P" means Standard & Poor's Rating Service.

         The credit  ratings to be utilized  for  purposes of this  Schedule are
those  assigned to the senior  unsecured  long-term  debt  securities  of Hughes
without  third-party  credit  enhancement,  and any rating assigned to any other
debt security of Hughes shall be disregarded.  The ratings in effect for any day
are those in effect at the close of business on such day.




                                        1





                               DISCLOSURE SCHEDULE


Section 1.01 -- FCC Licenses.



Section 4.03 -- Government Approvals.



Section 4.05 -- Litigation.



Section 4.07 -- Plans.



Section 4.10(c) -- Material Adverse Effect.



Section 4.13 -- Subsidiaries and Equity Investments.



Section 5.17 -- Existing Liens.



Section 5.25 -- Existing Indebtedness.




                                        1





                                                           EXHIBIT A -- Note



                                    TERM NOTE
                                                           New York, New York
                                                           [DATE]

         For value received,  American Mobile Satellite Corporation,  a Delaware
corporation   (the   "Borrower"),    promises   to   pay   to   the   order   of
______________________  (the "Bank"),  for the account of its Applicable Lending
Office,  the  unpaid  principal  amount  of each  Loan  made by the  Bank to the
Borrower pursuant to the Term Credit Agreement referred to below on the maturity
date  provided for in the Term Credit  Agreement.  The Borrower  promises to pay
interest  on the unpaid  principal  amount of each such Loan on the dates and at
the rate or rates provided for in the Term Credit  Agreement.  All such payments
of principal and interest  shall be made in lawful money of the United States in
Federal   or  other   immediately   available   funds  at  the   office  of  The
Toronto-Dominion Bank, 31 West 52nd Street, New York, New York.

         All Loans  made by the  Bank,  the  respective  Types  thereof  and all
repayments  of the  principal  thereof shall be recorded by the Bank and, if the
Bank  so  elects  in  connection  with  any  transfer  or  enforcement   hereof,
appropriate notations to evidence the foregoing information with respect to each
such Loan then outstanding may be endorsed by the Bank on the schedule  attached
hereto,  or on a  continuation  of such  schedule  attached  to and  made a part
hereof;  provided that the failure of the Bank to make any such  recordation  or
endorsement shall not affect the obligations of the Borrower  hereunder or under
the Term Credit Agreement.

         This note is one of the Notes referred to in the Term Credit  Agreement
dated as of March 31, 1998 among  American  Mobile  Satellite  Corporation,  the
banks party thereto, Morgan Guaranty Trust Company of New York, as Documentation
Agent and Toronto Dominion (Texas),  Inc. as  Administrative  Agent (as the same
may be amended from time to time, the "Term Credit Agreement"). Terms defined in
the Term Credit  Agreement are used herein with the same meanings.  Reference is
made to the Term Credit  Agreement for provisions for the prepayment  hereof and
the acceleration of the maturity hereof.



                            AMERICAN MOBILE SATELLITE
                            CORPORATION



                             By  ----------------------------------------------

                             Name:
                             Title:




                                        1






                         LOANS AND PAYMENTS OF PRINCIPAL

- -------------------------------------------------------------------------
                  Amount          Type           Amount of
                      of           of            Principal       Notation
Date                Loan          Loan             Repaid         Made By
- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------

- --------------------------------------------------------------------------




                                        3





                                EXHIBIT B -- Opinion of Counsel for the Borrower

                                   OPINION OF
                            COUNSEL FOR THE BORROWER



                                                              March __, 1998


To the Banks, Shareholder Guarantors and the Agents
Referred to Below
c/o Morgan Guaranty Trust Company
of New York, as Documentation Agent
60 Wall Street
New York, New York  10260

Dear Sirs:

         I am Vice  President,  Secretary and General Counsel of American Mobile
Satellite Corporation,  a Delaware corporation ("AMSC"). In such capacity I have
become familiar with the  $100,000,000  Term Credit  Agreement (the "Term Credit
Agreement")  dated as of March 31,  1998  among  AMSC,  the banks  listed on the
signature  pages  thereof,  Morgan  Guaranty  Trust  Company  of  New  York,  as
Documentation  Agent,  and Toronto  Dominion  (Texas),  Inc., as  Administrative
Agent.  Capitalized  terms not otherwise  defined herein shall have the meanings
set forth in the Term Credit  Agreement.  This opinion is being  rendered to you
pursuant to Section 3.1(a) of the Term Credit Agreement.

         In rendering this opinion, I have examined originals or copies of:

1.       the  Term  Credit  Agreement,  the  Notes  and  the Security and Pledge
         Agreement (collectively, the "Loan Documents");

2.       the certificate of incorporation, as amended, of AMSC;

3.       the bylaws, as amended, of AMSC;

4.       the  Certificate  of Good  Standing  with respect to AMSC issued by the
         Secretary  of State of the State of Delaware not earlier than March 20,
         1998;




                                        1





5.       the Certificate of Good Standing as a Foreign  Corporation with respect
         to AMSC issued by the State Corporation  Commission of the Commonwealth
         of Virginia dated March 20, 1998; and

6.       certain  resolutions  adopted  by the Board of  Directors  of AMSC at a
         meeting of the Board held on March 19, 1998;

upon all of which I have relied. I have not  independently  verified any factual
matters in connection with or apart from my review of the documents  referred to
above and,  accordingly,  I do not express any opinion as to matters  that might
have been disclosed by independent verification.

         In arriving at the opinions  expressed  below, I have assumed,  and not
verified, the authenticity of all documents submitted to me as originals and the
conformity to original documents of all documents  submitted to me as copies, as
well as the due and valid  authorization,  execution  and  delivery  of all such
documents by the appropriate party or parties (other than the Loan Parties), and
that each such party  (other than the  applicable  Loan  Parties)  has  adequate
power,  authority and legal right to enter into such  documents to which it is a
party and to  perform  its  obligations  under such  documents  to which it is a
party.

         Based solely upon the foregoing and in reliance thereon, and subject to
the  qualifications,  limitations  and  assumptions  set forth herein,  it is my
opinion that:

         1. AMSC is a corporation  duly  incorporated,  validly  existing and in
good  standing  under the laws of  Delaware,  has all  corporate  powers and all
material governmental licenses, authorizations,  consents and approvals required
to carry on its business as now  conducted,  and is duly  qualified as a foreign
corporation,  licensed and in good standing under the laws of each  jurisdiction
where its  ownership,  lease or  operation  of  property  or the  conduct of its
business require such qualification  except where the failure to be so qualified
would not reasonably be expected to result in a Material Adverse Effect.

         2. The execution,  delivery and  performance by AMSC of the Term Credit
Agreement,  the Notes and each other  Loan  Document  are  within its  corporate
powers,  have been duly authorized by all necessary  corporate action and do not
and will not: (a)  contravene  the terms of its  certificate  of  incorporation,
bylaws  or other  organization  documents;  (b)  conflict  with or result in any
breach or  contravention  of, or the creation of any Lien under,  any indenture,
agreement, lease, instrument,  Contractual Obligation, injunction, order, decree
or  undertaking  to which such  Person is a party  (other  than Liens  under the
Security and Pledge Agreement); or (c) violate any Requirement of Law.




                                        2





         3.  Each  Loan  Document  constitutes  the  legal,  valid  and  binding
obligations or agreements of AMSC, enforceable against it in accordance with its
terms.

         4. Except as set forth in Section 4.05 of the  Disclosure  Schedule and
for matters  arising  after the  Effective  Date which could not  reasonably  be
expected  to have a  Material  Adverse  Effect,  there  are no  actions,  suits,
proceedings,  claims  or  disputes  pending,  or to the  best of our  knowledge,
threatened  or  contemplated  at law, in equity,  in  arbitration  or before any
Governmental Authority,  against AMSC or any of its Subsidiaries or any of their
respective  properties  which:  (a)  purport  to affect or  pertain  to any Loan
Document, or any of the transactions  contemplated thereby; or (b) if determined
adversely  to AMSC or any of its  Subsidiaries,  could have a  Material  Adverse
Effect.  No injunction,  writ,  temporary  restraining order or any order of any
nature has been issued by any court or other Governmental  Authority  purporting
to enjoin or  restrain  the  execution,  delivery  and  performance  of any Loan
Document,  or  directing  that the  transactions  provided  for  therein  not be
consummated as therein provided.

         5.  None of  AMSC,  any  Person  controlling  AMSC,  or any  Subsidiary
thereof,  is (a) an  "Investment  Company"  within the meaning of the Investment
Company  Act of 1940;  or (b)  subject to  regulation  under the Public  Utility
Holding Company Act of 1935, or, to the best of our knowledge, the Federal Power
Act, the Interstate  Commerce Act, any state public  utilities code or any other
Federal  or  state  statute  or   regulation   limiting  its  ability  to  incur
Indebtedness.

         6.  Assuming  the Agents and the Banks have no knowledge of any adverse
claim thereto,  the Security and Pledge Agreement,  together with possession and
retention  in the  State  of New  York  by the  Administrative  Agent  of  stock
certificates evidencing the Pledged Stock (as defined in the Security and Pledge
Agreement),  together with the related duly executed and completed stock powers,
creates a valid and perfected  security  interest in the Pledged Stock under the
New York Uniform  Commercial Code in favor of the  Administrative  Agent for the
benefit  of  the  Secured  Parties  (as  defined  in  the  Security  and  Pledge
Agreement),  subject to the following:  the perfection and the  continuation  of
perfection  of the  Administrative  Agent's  security  interest  in  proceeds is
limited  to the  extent  set  forth in  Section  9-306  of the New York  Uniform
Commercial Code.

         7. The Security and Pledge  Agreement is in  acceptable  legal form for
the creation of enforceable security interests under the Uniform Commercial Code
of the  State of New York.  The  financing  statements  attached  hereto  are in
appropriate form for filing with the filing offices  specified  thereon.  To the
extent that a security  interest in the  Collateral  (as defined in the Security
and Pledge  Agreement) may be perfected by the filing of a financing  statement,
the security  interest in such  Collateral  will be perfected upon the filing of
such financing statements in such filing offices.




                                        3





         The opinions  set forth in this  paragraph 7 are subject to the further
qualification  that I express no opinion as to (i) AMSC's  rights in or title to
any Collateral;  and (ii) the priority of the  Administrative  Agent's  security
interest in the Collateral, and the opinions set forth in paragraphs 6 and 7 are
subject  to the  further  qualification  that I express no opinion as to (i) the
enforceability  of  provisions  in  the  Security  and  Pledge  Agreement  as to
self-help and non-judicial remedies, (ii) whether the procedures relating to the
sale or disposition of the Collateral in the Security and Pledge Agreement would
meet applicable  requirements  for a commercially  reasonable  disposition,  and
(iii) the  enforceability of the provisions in the Security and Pledge Agreement
relating to or purporting to limit the Administrative  Agent's duty with respect
to the Collateral.

         The  foregoing  opinions are subject to the following  assumptions  and
qualifications:

         (a) The  opinions set forth in paragraph 3 are subject to the effect of
any applicable  bankruptcy,  insolvency,  reorganization,  moratorium or similar
laws  affecting  creditors'  rights  generally  and  to  the  possible  judicial
application of foreign laws or governmental  action affecting the enforcement of
creditors' rights.

         (b) The  opinions  set forth in  paragraph 3 are subject to the further
qualification  that the enforceability of the obligations of AMSC under the Loan
Documents  are subject to general  principles of equity  (regardless  of whether
such  enforceability  is considered  in a proceeding in equity or at law).  Such
principles  of  equity  are  of  general   application  and,  in  applying  such
principles,  a  court,  among  other  things,  might  not  allow a  creditor  to
accelerate  the  maturity  of a debt upon the  occurrence  of a  default  deemed
immaterial  or might  decline  to  order  that a  covenant  be  performed.  Such
principles  applied by a court might include,  among other things, a requirement
that creditors act with  reasonableness and good faith. Such a requirement might
be applied,  among other  situations,  to the  provisions  of any Loan  Document
requiring  the payment of an indemnity or  compensation  to any party thereto or
purporting to authorize conclusive determinations by any party thereto.

         (c) With  respect  to my opinion in  paragraph  3 hereof,  I express no
opinion as to whether the courts of a  jurisdiction  other than the State of New
York would give effect to the choice of New York law as governing the agreements
as to which I express an opinion in paragraph 3.

         (d) The foregoing  opinions are limited to the laws of the State of New
York,  the General  Corporation  Law of the State of  Delaware,  the laws of the
Commonwealth  of Virginia  and the Federal law of the United  States  (except as
noted below),  and I do not express any opinion herein  concerning any other law
(including,  without limitation,  any such other law of any jurisdiction wherein





                                        4




any party to any of Loan  Document  may be located or deemed  located or wherein
enforcement of any such  documents may be sought).  I do not express any opinion
as to any matters arising under the Communications  Act of 1934, as amended,  or
any rules or  regulations  of the Federal  Communications  Commission.  I do not
express  any  opinion  as to  any  matters  (including  Governmental  Approvals)
relating  to  international  law,  including  compliance  by any Loan Party with
treaties  involving  the  International  Maritime  Satellite  Organization,  the
International  Telecommunications  Satellite  Organization and the International
Telecommunication  Union.  I am not a member of the Bar of the State of Delaware
and insofar as the opinions  expressed  herein  relate to matters of the General
Corporation  Law of the State of Delaware,  I have relied on the latest standard
compilations of statutes available to me.

         The opinions herein are rendered as of the date of this opinion,  and I
assume no obligation to revise or supplement this opinion at any date subsequent
hereto.

         The opinions  set forth above relate  solely to the matters as to which
my opinion has been  requested  by you,  and you must judge  whether the matters
addressed herein are sufficient for your purposes.  I do not express any opinion
as to any other matters.

         This opinion is rendered to the  Documentation  Agent and is solely for
its benefit, for the benefit of the Shareholder Guarantors,  and for the benefit
of any Bank party to the Term  Credit  Agreement  in  connection  with the above
transaction.  This opinion may not be relied upon by the Documentation Agent for
any other purpose, or furnished to, quoted to or relied upon by any other Person
other than any Bank or  Shareholder  Guarantor  referred  to in the  immediately
preceding sentence,  for any purpose without my prior written consent. It is not
to be filed with or furnished to any  Governmental  Authority or other Person in
either case without my prior written consent.

                                             Very truly yours,


                                             /s/Randy S. Segal
                                             Randy S. Segal
                                             General Counsel





                                        5





             EXHIBIT C -- Opinion of Special Counsel for the Agents


                                   OPINION OF
                             DAVIS POLK & WARDWELL,
                         SPECIAL COUNSEL FOR THE AGENTS


                                                     March __, 1998


To the Banks and the Agents
Referred to Below
c/o Morgan Guaranty Trust Company
of New York, as Documentation Agent
60 Wall Street
New York, New York  10260

Dear Sirs:

         We have participated in the preparation of the $100,000,000 Term Credit
Agreement  (the  "Term  Credit  Agreement")  dated as of March  31,  1998  among
American Mobile Satellite  Corporation,  a Delaware  corporation  ("AMSC"),  the
banks listed on the signature pages thereof (the "Banks"), Morgan Guaranty Trust
Company of New York, as Documentation Agent, and Toronto Dominion (Texas), Inc.,
as Administrative Agent (collectively,  the "Agents"), and have acted as special
counsel for the Agents for the purpose of  rendering  this  opinion  pursuant to
Section  3.01 of the Term  Credit  Agreement.  Terms  defined in the Term Credit
Agreement are used herein as therein defined.

         We have examined originals or copies, certified or otherwise identified
to our  satisfaction,  of such  documents,  corporate  records,  certificates of
public   officials  and  other   instruments   and  have  conducted  such  other
investigations  of fact and law as we have deemed  necessary  or  advisable  for
purposes of this opinion.

         Upon the basis of the  foregoing,  we are of the opinion that  assuming
that  the  execution,  delivery  and  performance  by  AMSC of the  Term  Credit
Agreement  and the Notes are  within  its  corporate  powers  and have been duly
authorized  by  all  necessary  corporate  action,  the  Term  Credit  Agreement
constitutes  a valid and binding  agreement of AMSC and each Note  constitutes a
valid and binding  obligation  of AMSC, in each case  enforceable  in accordance





                                        1




with its terms  except as may be limited by  bankruptcy,  insolvency  or similar
laws affecting creditors' rights generally and by general principles of equity.

         We are  members  of the Bar of the State of New York and the  foregoing
opinion is limited to the laws of the State of New York. In giving the foregoing
opinion,  we  express  no  opinion  as to the  effect (if any) of any law of any
jurisdiction  (except the State of New York) in which any Bank is located  which
limits the rate of interest that such Bank may charge or collect.

         This  opinion is rendered  solely to you in  connection  with the above
matter.  This  opinion  may not be relied  upon by you for any other  purpose or
relied upon by any other person without our prior written consent.

                                Very truly yours,




                                        2





                EXHIBIT D -- Assignment and Assumption Agreement



                       ASSIGNMENT AND ASSUMPTION AGREEMENT

         AGREEMENT  dated as of  _________,  19__ among [NAME OF ASSIGNOR]  (the
"Assignor"),  [NAME OF ASSIGNEE] (the  "Assignee"),  AMERICAN  MOBILE  SATELLITE
CORPORATION   (the   "Borrower")  and  TORONTO   DOMINION   (TEXAS),   INC.,  as
Administrative Agent (the "Agent").

         WHEREAS,  this  Assignment and Assumption  Agreement (the  "Agreement")
relates to the  $100,000,000  Term Credit  Agreement  dated as of March 31, 1998
among the Borrower,  the Assignor and the other Banks party  thereto,  as Banks,
Morgan Guaranty Trust Company of New York, as Documentation Agent, and the Agent
(the "Credit Agreement");

         WHEREAS,  Loans made to the Borrower by the  Assignor  under the Credit
Agreement in the aggregate  principal  amount of $__________  are outstanding at
the date hereof; and

         WHEREAS,  the  Assignor  proposes to assign to the  Assignee all of the
rights of the Assignor under the Credit Agreement in respect of a portion of its
outstanding  Loans in a principal  amount equal to  $__________  (the  "Assigned
Amount"),  and the  Assignee  proposes to accept  assignment  of such rights and
assume the corresponding obligations from the Assignor on such terms;

         NOW,  THEREFORE,  in  consideration  of the  foregoing  and the  mutual
agreements contained herein, the parties hereto agree as follows:

         1.  Definitions.  All capitalized  terms not otherwise  defined herein
shall have the respective meanings set forth in the Credit Agreement.

         2.  Assignment.  The Assignor  hereby assigns and sells to the Assignee
all of the rights of the  Assignor  under the Credit  Agreement to the extent of
the Assigned  Amount,  and the Assignee  hereby accepts such assignment from the
Assignor and assumes all of the  obligations  of the  Assignor  under the Credit
Agreement to the extent of the Assigned Amount,  including the purchase from the
Assignor of the corresponding  portion of the principal amount of the Loans made
by the Assignor  outstanding at the date hereof. Upon the execution and delivery
hereof by the  Assignor,  the  Assignee,  [the  Borrower  and the Agent] and the





                                        1




payment of the  amounts  specified  in Section 3 required to be paid on the date
hereof (i) the Assignee shall, as of the date hereof,  succeed to the rights and
be obligated  to perform the  obligations  of a Bank under the Credit  Agreement
with a  Commitment  in an  amount  equal to the  Assigned  Amount,  and (ii) the
Commitment of the Assignor  shall,  as of the date hereof,  be reduced by a like
amount and the Assignor released from its obligations under the Credit Agreement
to the extent such obligations have been assumed by the Assignee. The assignment
provided for herein shall be without recourse to the Assignor.

         3. Payments.  As consideration for the assignment and sale contemplated
in Section 2 hereof,  the Assignee  shall pay to the Assignor on the date hereof
in Federal funds the amount  heretofore  agreed  between them.1 It is understood
that  commitment  and/or  facility  fees  accrued to the date hereof are for the
account of the  Assignor  and such fees  accruing  from and  including  the date
hereof  are for the  account  of the  Assignee.  Each  of the  Assignor  and the
Assignee hereby agrees that if it receives any amount under the Credit Agreement
which is for the account of the other party  hereto,  it shall  receive the same
for the account of such other party to the extent of such other party's interest
therein and shall promptly pay the same to such other party.

         [4.  Consent  of  the  Borrower  and  the  Agent.   This  Agreement  is
conditioned  upon the consent of the Borrower and the Agents pursuant to Section
9.06 of the Credit  Agreement.  The execution of this  Agreement by the Borrower
and the Agents is  evidence  of this  consent.  Pursuant  to Section  2.03,  the
Borrower  agrees  to  execute  and  deliver a Note  payable  to the order of the
Assignee to evidence the assignment and assumption provided for herein.]

         5.  Non-Reliance on Assignor.  The Assignor makes no  representation or
warranty in connection with, and shall have no  responsibility  with respect to,
the  solvency,  financial  condition,  or  statements  of  the  Borrower  or the
Borrower,  or the validity and enforceability of the obligations of the Borrower
in respect of the Credit Agreement or any Note. The Assignee  acknowledges  that
it has,  independently  and without reliance on the Assignor,  and based on such
documents  and  information  as it has deemed  appropriate,  made its own credit
analysis  and  decision  to enter into this  Agreement  and will  continue to be
responsible  for making its own independent  appraisal of the business,  affairs
and financial condition of the Borrower.
- --------
         1 Amount should combine  principal  together with accrued  interest and
breakage compensation, if any, to be paid by the Assignee, net of any portion of
any upfront fee to be paid by the Assignor to the Assignee. It may be preferable
in an appropriate case to specify these amounts generically or by formula rather
than as a fixed sum.




                                        2





         6. Governing Law. This Agreement  shall be governed by and construed in
accordance with the laws of the State of New York.

         7.  Counterparts.  This  Agreement  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.

         IN WITNESS  WHEREOF,  the  parties  have caused  this  Agreement  to be
executed and  delivered by their duly  authorized  officers as of the date first
above written.

                               [NAME OF ASSIGNOR]


                               By   --------------------------------------------

                               Name:
                               Title:


                               [NAME OF ASSIGNEE]


                               By   --------------------------------------------

                               Name:
                               Title:


                               AMERICAN MOBILE SATELLITE
                               CORPORATION


                               By   --------------------------------------------

                               Name:
                               Title:


                               TORONTO DOMINION (TEXAS), INC.,
                               as Administrative Agent


                               By   --------------------------------------------

                               Name:
                               Title:

                                        3