Registration No.333-


                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549
                              ---------------------


                                    FORM S-8


                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                              ---------------------

                      AMERICAN MOBILE SATELLITE CORPORATION
               (Exact name of issuer as specified in its charter)

                                    Delaware
                         (State or other jurisdiction of
                         incorporation or organization)
                                   93-0976127
                                (I.R.S. Employer
                               Identification No.)


                            10802 Parkridge Boulevard
                           Reston, Virginia 20191-5416
                                  703-758-6000
                     (Address of Principal Executive Offices
                    including Zip Code, and telephone number,
        including Area Code of registrant's principal executive offices)

          American Mobile Satellite Corporation 1989 Stock Option Plan
                            (Full title of the Plan)

                              Randy S. Segal, Esq.
                  General Counsel, Vice President and Secretary
                      American Mobile Satellite Corporation
                            10802 Parkridge Boulevard
                           Reston, Virginia 20191-5416
                                  703-758-6000

                     (Name, address, including Zip Code, and
               telephone number, including Area Code, of agent for
                                    service)



                  Approximate date of commencement of proposed
                    sale of the securities: From time to time
                        after the effective date of this
                             Registration Statement.


<PAGE>



                         CALCULATION OF REGISTRATION FEE
================================================================================

                                   Proposed
                                   Maximum      Proposed
Title of                           Offering     Maximum
securities         (1) Amount      Price        Aggregate        Amount of
to be                  to be       Per          Offering       registration
registered          registered     Share        Price               fee
--------------------------------------------------------------------------------
Common
Stock
par value
$.01 per            1,000,000      (2)          $11,500,000    $3,432.84
share.....          shares

================================================================================
(1)      Represents  the  maximum  number  of  additional  shares  which  may be
         distributed pursuant to this Registration  Statement,  absent operation
         of   recapitalization   provisions   of  the  Plan.   Such   additional
         undeterminable  number of shares as may be  required  by reason of such
         recapitalization provisions is hereby also registered.

(2)      Not applicable.


                                       -2-

<PAGE>









     The contents of Registration  Statements No. 33-72852, No. 33-34250 and No.
333-30099 are hereby incorporated by reference.



                                       -3-

<PAGE>



Item 8.           Exhibits


Exhibits                 Description of Exhibit
--------                 ----------------------


4.6       --   1989 Employee Stock Option Plan as amended May 20, 1998.
               (Filed herewith.)

5         --   Opinion of Randy S. Segal, General Counsel of the Company, as
               to the validity of the securities being offered.(Filed herewith.)

23(a)     --   Consent of Arthur Andersen LLP. (Filed herewith.)

23(b)     --   Consent of Randy S. Segal, General Counsel of the Company
               (included in Exhibit 5).

24        --   Powers of Attorney (included on signature pages).

                                        -4-

<PAGE>




                                   SIGNATURES

             Pursuant to the  requirements  of the  Securities  Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing a Form S-8 and has duly caused this  Registration
Statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized, in the County of Fairfax, Commonwealth of Virginia, on May 20, 1998.

                                         AMERICAN MOBILE SATELLITE CORPORATION


                                       By:  /s/Gary M. Parsons
                                            ------------------
                                            Gary M. Parsons
                                            Chief Executive Officer



                                POWER OF ATTORNEY

             KNOW ALL MEN BY THESE  PRESENTS,  that each person whose  signature
appears  below  hereby  constitutes  and  appoints  Gary M.  Parsons,  Walter V.
Purnell, Jr. and Randy S. Segal, his true and lawful attorney-in-fact and agent,
with full power of  substitution  and  resubstitution,  for him and in his name,
place and stead,  in any and all  capacities,  to sign any and all amendments to
this registration  statement,  and to file the same , with exhibits thereto, and
other  documents  in  connection  therewith  with the  Securities  and  Exchange
Commission,  granting  unto  said  attorney-in-fact  and  agent  full  power and
authority to do and perform each and every act and thing requisite and necessary
to be done,  as fully to all and intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorney-in-fact and agent
or either of them, or their or his substitute or substitutes, may lawfully do or
cause to be done by virtue hereof.



                                      - 5 -

<PAGE>



             Pursuant to the  requirements  of the Securities Act of 1933,  this
Registration  Statement  has been signed below by the  following  persons in the
capacities and on the dates indicated:


       Name                       Title                           Date
       ----                       -----                           ----

/s/Gary M. Parsons              Chairman of the Board       May 20, 1998
-----------------               of Directors (Principal  
Gary M. Parsons                 Executive Officer)


/s/Stephen D. Peck              Chief Financial Officer     May 20, 1998
------------------              and President (Principal
Stephen D. Peck                 Financial and Accounting
                                Officer)


/s/Douglas I. Brandon           Director                    May 20, 1998
---------------------
Douglas I. Brandon


/s/Ho Siaw Hong                 Director                    May 20, 1998   
--------------------
Ho Siaw Hong


                                Director                    May 20, 1998  
------------------
Pradeep P. Kaul



/s/Billy J. Parrott             Director                    May 20, 1998  
-------------------
Billy J. Parrott


                                Director                    May 20, 1998  
---------------------
Andrew A. Quartner


/s/Jack A. Shaw                 Director                    May 20, 1998
---------------                 
Jack A. Shaw


/s/Roderick M. Sherwood, III    Director                    May 20, 1998  
----------------------------
Roderick M. Sherwood, III


/s/Michael T. Smith             Director                    May 20, 1998  
-------------------
Michael T. Smith


                                Director                    May 20, 1998  
-----------------
Yap Chee Keong


                                      - 6 -

<PAGE>



                                INDEX TO EXHIBITS


Exhibits                      Description of Exhibit                    
                                                       
4.6      --   1989 Employee Stock Option Plan as amended May 20,
              1998.  (Filed herewith.)

5        --   Opinion of Randy S. Segal, General Counsel of the 
              Company, as to the validity of the securities being 
              offered. (Filed herewith.)

23(a)    --   Consent of Arthur Andersen & Co. (Filed herewith.)

23(b)    --   Consent of Randy S. Segal,  General Counsel of the 
              Company  (included in Exhibit 5).

24       --   Powers of Attorney (included on signature pages).


                                     - 7 -

<PAGE>
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{"company-data": {"conformed-name": "AMERICAN MOBILE SATELLITE CORP", "cik": "0000913665", "assigned-sic": "4899", "irs-number": "930976127", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-53253", "film-number": "98629526"}, "business-address": {"street1": "10802 PARKRIDGE BLVD", "city": "RESTON", "state": "VA", "zip": "22091", "phone": "7037586000"}, "mail-address": {"street1": "10802 PARKRIDGE BLVD", "city": "RESTON", "state": "VA", "zip": "22091"}}
Registration No.333-

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549
                              ---------------------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                              ---------------------

                      AMERICAN MOBILE SATELLITE CORPORATION
               (Exact name of issuer as specified in its charter)

                                    Delaware
                         (State or other jurisdiction of
                         incorporation or organization)
                                   93-0976127
                                (I.R.S. Employer
                               Identification No.)

                            10802 Parkridge Boulevard
                           Reston, Virginia 20191-5416
                                  703-758-6000
                     (Address of Principal Executive Offices
                    including Zip Code, and telephone number,
        including Area Code of registrant's principal executive offices)

          American Mobile Satellite Corporation 1989 Stock Option Plan
                            (Full title of the Plan)

                              Randy S. Segal, Esq.
                  General Counsel, Vice President and Secretary
                      American Mobile Satellite Corporation
                            10802 Parkridge Boulevard
                           Reston, Virginia 20191-5416
                                  703-758-6000

                     (Name, address, including Zip Code, and
               telephone number, including Area Code, of agent for
                                    service)

                  Approximate date of commencement of proposed
                    sale of the securities: From time to time
                        after the effective date of this
                             Registration Statement.
CALCULATION OF REGISTRATION FEE
================================================================================

                                   Proposed
                                   Maximum      Proposed
Title of                           Offering     Maximum
securities         (1) Amount      Price        Aggregate        Amount of
to be                  to be       Per          Offering       registration
registered          registered     Share        Price               fee
--------------------------------------------------------------------------------
Common
Stock
par value
$.01 per            1,000,000      (2)          $11,500,000    $3,432.84
share.....          shares

================================================================================
(1)      Represents  the  maximum  number  of  additional  shares  which  may be
         distributed pursuant to this Registration  Statement,  absent operation
         of   recapitalization   provisions   of  the  Plan.   Such   additional
         undeterminable  number of shares as may be  required  by reason of such
         recapitalization provisions is hereby also registered.

(2)      Not applicable.

                                       -2-
The contents of Registration  Statements No. 33-72852, No. 33-34250 and No.
333-30099 are hereby incorporated by reference.

                                       -3-
Item 8.           Exhibits

Exhibits                 Description of Exhibit
--------                 ----------------------

4.6       --   1989 Employee Stock Option Plan as amended May 20, 1998.
               (Filed herewith.)

5         --   Opinion of Randy S. Segal, General Counsel of the Company, as
               to the validity of the securities being offered.(Filed herewith.)

23(a)     --   Consent of Arthur Andersen LLP. (Filed herewith.)

23(b)     --   Consent of Randy S. Segal, General Counsel of the Company
               (included in Exhibit 5).

24        --   Powers of Attorney (included on signature pages).

                                        -4-
SIGNATURES

             Pursuant to the  requirements  of the  Securities  Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing a Form S-8 and has duly caused this  Registration
Statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized, in the County of Fairfax, Commonwealth of Virginia, on May 20, 1998.

                                         AMERICAN MOBILE SATELLITE CORPORATION

                                       By:  /s/Gary M. Parsons
                                            ------------------
                                            Gary M. Parsons
                                            Chief Executive Officer

                                POWER OF ATTORNEY

             KNOW ALL MEN BY THESE  PRESENTS,  that each person whose  signature
appears  below  hereby  constitutes  and  appoints  Gary M.  Parsons,  Walter V.
Purnell, Jr. and Randy S. Segal, his true and lawful attorney-in-fact and agent,
with full power of  substitution  and  resubstitution,  for him and in his name,
place and stead,  in any and all  capacities,  to sign any and all amendments to
this registration  statement,  and to file the same , with exhibits thereto, and
other  documents  in  connection  therewith  with the  Securities  and  Exchange
Commission,  granting  unto  said  attorney-in-fact  and  agent  full  power and
authority to do and perform each and every act and thing requisite and necessary
to be done,  as fully to all and intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorney-in-fact and agent
or either of them, or their or his substitute or substitutes, may lawfully do or
cause to be done by virtue hereof.

                                      - 5 -
Pursuant to the  requirements  of the Securities Act of 1933,  this
Registration  Statement  has been signed below by the  following  persons in the
capacities and on the dates indicated:

       Name                       Title                           Date
       ----                       -----                           ----

/s/Gary M. Parsons              Chairman of the Board       May 20, 1998
-----------------               of Directors (Principal  
Gary M. Parsons                 Executive Officer)

/s/Stephen D. Peck              Chief Financial Officer     May 20, 1998
------------------              and President (Principal
Stephen D. Peck                 Financial and Accounting
                                Officer)

/s/Douglas I. Brandon           Director                    May 20, 1998
---------------------
Douglas I. Brandon

/s/Ho Siaw Hong                 Director                    May 20, 1998   
--------------------
Ho Siaw Hong

                                Director                    May 20, 1998  
------------------
Pradeep P. Kaul

/s/Billy J. Parrott             Director                    May 20, 1998  
-------------------
Billy J. Parrott

                                Director                    May 20, 1998  
---------------------
Andrew A. Quartner

/s/Jack A. Shaw                 Director                    May 20, 1998
---------------                 
Jack A. Shaw

/s/Roderick M. Sherwood, III    Director                    May 20, 1998  
----------------------------
Roderick M. Sherwood, III

/s/Michael T. Smith             Director                    May 20, 1998  
-------------------
Michael T. Smith

                                Director                    May 20, 1998  
-----------------
Yap Chee Keong

                                      - 6 -
INDEX TO EXHIBITS

Exhibits                      Description of Exhibit                    
                                                       
4.6      --   1989 Employee Stock Option Plan as amended May 20,
              1998.  (Filed herewith.)

5        --   Opinion of Randy S. Segal, General Counsel of the 
              Company, as to the validity of the securities being 
              offered. (Filed herewith.)

23(a)    --   Consent of Arthur Andersen & Co. (Filed herewith.)

23(b)    --   Consent of Randy S. Segal,  General Counsel of the 
              Company  (included in Exhibit 5).

24       --   Powers of Attorney (included on signature pages).

                                     - 7 -