Document:

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                                                                    EXHIBIT 10.6

                          [AMERICAN MOBILE LETTERHEAD]

                      AMERICAN MOBILE SATELLITE CORPORATION
                                STOCK AWARD PLAN
                     AMENDED AND RESTATED JANUARY 27, 2000

1.   DEFINITIONS

     In this Plan, except where the context otherwise indicates, the following
definitions apply:

     A.   "Agreement" means a written agreement implementing a grant of an
          Option or an award of Bonus Stock.

     B.   "Board" means the Board of Directors of the Corporation.

     C.   "Bonus Stock" means Shares awarded under the Plan in accordance with
          the terms of Article 9.

     D.   "Code" means the Internal Revenue Code of 1986, as amended.

     E.   "Committee" means the committee of the Board meeting the standards of
          Rule 16b-3(c)(2)(i) under the Exchange Act, or any similar successor
          rule, appointed by the Board to administer the Plan. Unless otherwise
          determined by the Board, the Compensation Committee of the Board shall
          be the Committee.

     F.   "Common Stock" means the common stock, par value $.01 per share, of
          the Corporation.

     G.   "Corporation" means AMERICAN MOBILE SATELLITE CORPORATION.

     H.   "Date of Exercise" means the date on which the Corporation receives
          notice of the exercise of an Option in accordance with the terms of
          Article 7.

     I.   "Date of Grant" means the date as of which an Option is granted or an
          award of Bonus Stock is authorized by the action of the Committee or
          such later date as may be specified in the authorization.
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     J.   "Employee" means any person determined by the Committee to be an
          employee of the Corporation or of a Subsidiary.

     K.   "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     L.   "Fair Market Value" of a Share means the amount equal to the average
          of the high and low prices of a Share on the applicable date as
          reported by the consolidated tape of the National Association of
          Securities Dealers Automated Quotation (or on such other recognized
          quotation system on which the trading prices of the Common Stock are
          quoted on the applicable date), or, if no Share transactions are
          reported on such tape (or such other system) on the applicable
          date, the high and low prices of a Share on the immediately preceding
          date on which Share transactions were so reported, or as determined
          pursuant to a reasonable method adopted by the Committee in good faith
          for such purpose.

     M.   "Grantee" means an Employee to whom bonus Stock has been awarded.

     N.   "Insider" means an Optionee or Grantee who is subject to the reporting
          requirements under Section 16(a) of the Exchange Act.

     O.   "Option" means an option to purchase Shares granted under the Plan in
          accordance with the terms of Article 6.

     P.   "Option Period" means the period during which an Option may be
          exercised.

     Q.   "Option Price" means the price per Share at which an Option may be
          exercised. The Option Price shall not be less than the greater of the
          Fair Market Value per Share determined as of the Date of Grant or the
          par value of the Common Stock.

     R.   "Optionee" means an Employee to whom an Option has been granted.

     S.   "Plan" means this AMERICAN MOBILE SATELLITE CORPORATION Stock Award
          Plan.

     T.   "Reload Option" means a new Option granted to an Optionee upon the
          surrender of Shares to pay the Option Price of a previously granted
          Option. The Option Price for any Reload Option shall not be less than
          the greater of the Fair Market Value of a Share on the date that
          Shares are surrendered in payment of the Option Price in accordance
          with Section 3.A(d) or the par value of the Common Stock. Other terms
          of the Reload Option shall be the

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          same as the terms contained in the Optionee's Agreement relating to
          the Option being exercised.

     U.   "Share" means a share of Common Stock.

     V.   "Subsidiary" means a corporation at least 50% of the total combined
          voting power of all classes of stock of which is owned by the
          Corporation either directly or through one or more Subsidiaries.

     W.   "Withholding Tax Liabilities" means the Corporation's federal, state
          and any local income tax and payroll withholding tax obligations
          arising in connection with the exercise of an Option or the award of
          Bonus Stock under the Plan. Withholding Tax Liabilities does not
          include the Corporation's share of any payroll taxes.

2.   PURPOSE

     The Plan is intended to assist in attracting and retaining Employees of
outstanding ability and to promote the identification of their interests with
those of the shareholders of the Corporation.

3.   ADMINISTRATION

     The Plan shall be administered by the Committee. In addition to any other
powers granted to the Committee, it shall have the following powers, subject to
the express provisions of the Plan:

     A.   subject to the provisions of this Plan, to determine in its discretion
          the Employees to whom options shall be granted and to whom Bonus
          Stock shall be awarded, the number of Shares to be subject to each
          Option or Bonus Stock award, and the terms upon which Options may be
          acquired and exercised and the terms and conditions of Bonus Stock
          awards

     B.   to determine all other terms and provisions of each Agreement, which
          need not be identical;

     C.   without limiting the generality of the foregoing, to provide in its
          discretion in an Agreement:

          a.   for an agreement by the Optionee or Grantee to render services
               to the Corporation upon such terms and conditions as may be
               specified in the

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               Agreement, provided that the Committee shall not have the power
               to commit the Corporation to employ or otherwise retain any
               Optionee or Grantee;

          b.   for restrictions on the transfer, sale or other disposition of
               Shares issued to the Optionee upon the exercise of an Option or
               for other restrictions permitted by Article 9 with respect to
               Bonus Stock;

          c.   for an agreement by the Optionee or Grantee to resell to the
               Corporation, under specified conditions, Shares issued upon the
               exercise of an Option or awarded as Bonus Stock;

          d.   for the right of the Optionee to surrender to the Corporation an
               Option (or a portion thereof) that has become exercisable and
               receive upon such surrender, without any payment to the
               Corporation or a Subsidiary (other than amounts necessary to
               satisfy Withholding Tax Liabilities with respect to the Option)
               that number of Shares (equal to the highest whole number of
               Shares) having an aggregate Fair Market Value as of the date of
               surrender equal to that number of Shares subject to the Option
               (or portion thereof) being surrendered multiplied by an amount
               equal to the excess of (i) the Fair Market Value of a Share on
               the date of surrender over (ii) the Option Price, plus an amount
               of cash equal to the Fair Market Value of any fractional Share to
               which the Optionee might be entitled; any such surrender shall be
               treated as the exercise of the Option (or portion thereof); and

          e.   for the automatic issuance of a Reload Option covering a number
               of Shares equal to the number of any Shares used to pay the
               Option Price;

     D.   to construe and interpret the Agreements and the Plan;

     E.   to require, whether or not provided for in the pertinent Agreement, of
          any person exercising an Option or acquiring Shares of Bonus Stock, at
          the time of such exercise or acquisition, the making of any
          representations or agreements which the Committee may deem necessary
          or advisable in order to comply with the securities laws or the United
          States or of any state; and

     F.   to make all other determinations and take all other actions necessary
          or advisable for the administration of the Plan.

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     Any determinations or actions made or taken by the Committee pursuant to
this Article shall, subject to the express provisions of this Plan, be binding
and final.

4.   ELIGIBILITY

     Options and Bonus Stock may be granted or awarded only to Employees,
provided, however, that members or the Committee are not eligible to receive
Options or Bonus Stock. Subject to the limitations of Section 5.A, an Employee
who has been granted an Option or Bonus Stock may be granted additional Options
or Bonus Stock.

5.   STOCK SUBJECT TO THE PLAN

     A.   Subject to adjustment as provided in Article 11, an aggregate of
          5,500,000 authorized and unissued Shares, reissued treasury Shares, or
          Shares otherwise acquired by the Corporation, may be issued under the
          Plan upon the exercise of Options or pursuant to awards of Bonus
          Stock, provided, however, that no Employee may be granted Options and
          awarded Bonus Stock covering more than 50% of the number of Shares
          issuable under the Plan.

     B.   If an Option expires or terminates for any reason without having
          been fully exercised, or if Shares of Bonus Stock are forfeited, the
          unpurchased Shares which had been subject to the Option at the time of
          its expiration or termination, or the forfeited Shares of Bonus Stock,
          shall become available for the grant of other Options or for the award
          of additional Shares of Bonus Stock, provided, that in the case of
          forfeited Shares and to the extent necessary to satisfy the provisions
          of Rule 16b-3 under the Exchange Act, the Grantee has received no
          dividends prior to forfeiture with respect to such Shares.

6.   OPTIONS

     A.   Subject to the provisions of this Plan, the Committee is hereby
          authorized to grant Options to Employees.

     B.   All Agreements granting Options shall contain a statement that
          the Option is intended to be a nonstatutory stock option and not an
          incentive stock option as defined in section 422 of the Code.

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     C.   The Option Period shall be determined by the Committee and
          specifically set forth in the Agreement, provided, however, that an
          Option shall not be exercisable before six months from the Date of
          Grant (except that this limitation need not apply in the event of the
          death of the Optionee within the six-month period) and no Option shall
          be exercisable after ten years after the Date of Grant.

     D.   By accepting the grant of an Option under the Plan, each Optionee
          agrees, for the Optionee and his or her successors, that the Option
          may not be exercised at any time that the Corporation does not have in
          effect a registration statement under the Securities Act of 1933, as
          amended, relating to the offer of Common Stock to the Optionee under
          the Plan, unless the Corporation agrees to permit such exercise, and
          that, upon the issuance of any Shares upon the exercise of the Option,
          the Optionee will, upon the request of the Corporation, agree in
          writing that he or she is acquiring such Shares for investment only
          and not with a view to resale, and that he or she will not sell,
          pledge or otherwise dispose of such Shares so issued unless and until
          (i) the Corporation is furnished with an opinion of counsel to the
          effect that registration of such Shares pursuant to the Securities Act
          of 1933, as amended, is not required by that Act and the rules and
          regulations thereunder; (ii) the staff of the Securities and Exchange
          Commission has issued a "no-action" letter with respect to such
          disposition; or (iii) such registration or notification as is, in the
          opinion of counsel for the Corporation, required for the lawful
          disposition of such Shares has been filed by the Corporation and has
          become effective; provided, however, that the Corporation shall not be
          obligated to file any such registration or notification. The Option
          shall further agree that the Company may place a legend embodying such
          restriction on the certificates evidencing such shares.

     E.   All other terms of Options granted under the Plan shall be
          determined by the Committee in its sole discretion, as exercised
          consistently with the terms of the Plan, and specifically set forth in
          the Optionee's agreement. Any terms of Options determined by the
          Committee that vary from the express terms set forth in the Plan also
          shall be specifically set forth in the Optionee's Agreement.

7.   EXERCISE

     A.   An Option may, subject to the provisions of the Agreement under
          which it was granted, be exercised in whole or in part by the delivery
          to the Corporation of written notice of the exercise, in such form as
          the Committee may prescribe, accompanied by full payment of the Option
          Price for the

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          Shares with respect to which the Option is exercised in accordance
          with Section 7.B, and by satisfaction by the Optionee of Withholding
          Tax Liabilities in accordance with Article 10.

     B.   The Option Price may be paid in the form of (i) cash, which may
          include an assignment of the right to receive cash proceeds of the
          sale of Common Stock subject to the Option pursuant to a "cashless
          exercise" of the Option through a transaction with a broker, (ii) duly
          endorsed certificates representing Shares (other than Shares that are
          subject to a substantial risk of forfeiture) having a Fair Market
          Value on the Date of Exercise aggregating not more than the portion of
          the Option Price being paid by delivery of such Shares, or (iii) a
          combination of cash and Shares as provided in Sections 7.B(i) and
          (ii).

     C.   To the extent required to comply with Treasury Regulation
          Section 1.401(k)-1(d)(2)(iv)(B)(4), or any amendment or successor
          thereto, an Optionee's "elective and employee contributions" (within
          the meaning of such Treasury Regulation) under the Plan shall be
          suspended for a period of twelve months following such Optionee's
          receipt of a hardship distribution made in reliance on such Treasury
          Regulation from any plan containing a cash or deferred arrangement
          under Section 401(k) of the Code maintained by the Corporation or a
          related party within the provisions of subsections (b), (c), (m) or
          (o) of Section 414 of the Code.

8.   NONTRANSFERABILITY

     Options granted under the Plan shall not be transferable otherwise than
(a) by will or the laws of descent and distribution, or (b) pursuant to a
qualified domestic relations order as defined in Section 414(p) of the Code or
Title I of the Employee Retirement Income Security Act or the rules thereunder,
and an Option may be exercised, during the Optionee's lifetime, only by the
Optionee or, in the case of the Optionee's legal disability, by the Optionee's
legal representative.

9.   BONUS STOCK

     A.   Subject to the provisions of this Plan, the Committee is hereby
          authorized to award Bonus Stock to Employees.

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     B. Bonus Stock shall be Shares that shall be issued at such times, subject
        to achievement of such performance or other goals and on such other
        terms and conditions as the Committee shall deem appropriate.

10.  SATISFACTION OF WITHHOLDING TAX LIABILITIES

Each Optionee or Grantee must provide the Corporation with the means to satisfy
the Corporation's Withholding Tax Liabilities, with respect to any income
recognized by the Optionee or Grantee as a result of the exercise of an Option
or award of Bonus Stock. Unless otherwise determined by the Committee and
specifically set forth in the Optionee's or Grantee's Agreement, an Option or
Grantee may satisfy Withholding Tax Liabilities by (i) delivering cash to the
Corporation, (ii) electing to have the Corporation retain Shares otherwise
issuable on the exercise of the Option or pursuant to the award of Bonus Stock
(other than Shares that are subject to a substantial risk of forfeiture),
(iii) delivering shares (other than Shares that are subject to a substantial
risk of forfeiture) to the Corporation, or (iv) electing to satisfy Withholding
Tax Liabilities through a combination of clauses (i), (ii) or (iii) of this
Article 10. Satisfaction of Withholding Tax Liabilities also shall be
accomplished under such additional reasonable terms and conditions as the
Committee deems appropriate. Unless otherwise determined by the Committee and
specifically set forth in the Optionee's or Grantee's Agreement, in the case of
an Insider who elects to satisfy Withholding Tax Liabilities by having the
Corporation retain Shares otherwise issuable on the exercise of an Option or
pursuant to an award to Bonus Stock, the Insider shall have the right to so
satisfy Withholding Tax Liabilities through (a) an irrevocable election made at
least six months in advance of the date on which the Withholding Tax Liabilities
arise, and (b) if the Withholding Tax Liabilities arise during the ten business
day period beginning on the third business day following the public release of
the Corporation's quarterly or annual earnings ("Window Period"), an irrevocable
election made during such Window Period.

11.  CAPITAL ADJUSTMENTS

     The number and class of Shares subject to each outstanding Option or award
of Bonus Stock, the Option Price and the aggregate number and class of Shares
for which grants or awards thereafter may be made shall be equitably adjusted by
the Committee to reflect such events as stock dividends, stock splits,
extraordinary cash dividends, adoption of stock rights plans, split-ups,
split-offs, spin-offs, liquidations, combinations or exchange of shares,
recapitalizations, mergers, consolidations, reorganizations or any similar
transaction of or by the Corporation.

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12.   TERMINATION OR AMENDMENT

      The Board shall have the power to terminate the Plan and to amend it in
any respect, provided that, after the Plan has been approved by the shareholders
of the Company, the Board may not, without the approval of the shareholders of
the Company if such approval is then required by applicable law or in order for
the Plan to continue to satisfy the requirements of Rule 16b-3 under the
Exchange Act, amend the Plan so as to increase materially the number of Shares
that may be issued under the Plan (except as provided in Article 11), to modify
materially the requirements as to eligibility for participation in the Plan, or
to increase materially the benefits accruing to participants under the Plan. No
termination or amendment of the Plan shall, without his or her consent,
adversely affect the rights or obligations of any Optionee or Grantee.

13.   MODIFICATION, EXTENSION AND RENEWAL OF OPTIONS AND BONUS STOCK

      Subject to the terms and conditions and within the limitations of the
Plan, the Committee may modify, extend or renew outstanding Options, or accept
the surrender of outstanding Options (to the extent not theretofore exercised)
granted under the Plan or under any other plan of the Corporation, or a company
or similar entity acquired by the Corporation or a Subsidiary, and authorize the
granting of new Options (to the extent not theretofore exercised), pursuant to
the Plan in substitution therefor and the substituted Options may specify a
lower exercise price than the surrendered Options, a longer term than the
surrendered Options or have any other provisions that are authorized by the
Plan. Subject to the terms and conditions and within the limitations of the
Plan, the Committee may modify the terms of any outstanding Agreement providing
for an award of Bonus Stock. Notwithstanding the foregoing, however, no
modification of an Option granted under the Plan, or an award of Bonus Stock,
shall, without the consent of the Optionee or Grantee, alter or impair any of
the Optionee's or Grantee's right or obligations.

14.   EFFECTIVENESS OF THE PLAN

      The Plan and any amendments requiring shareholder approval pursuant to
Article 12 are subject to approval by vote of the shareholders of the
Corporation within 12 months after their adoption by the Board. Subject to that
approval, the Plan and any amendments are effective on the date on which they
are adopted by the Board. Options and Bonus Stock may be granted or awarded
prior to shareholder approval of the Plan or amendments, but each such Option or
Bonus Stock grant or award shall be subject to the approval of the Plan or
amendments by the shareholders. Except to the extent required to satisfy the
requirements of Rule 16b-3 under the Exchange Act, the date on which any Option
or Bonus Stock granted or awarded prior to shareholder approval of the Plan or
amendment is granted or awarded shall be the Date of Grant for all purposes as
if the

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Option or Bonus Stock had not been subject to approval. No Option may be
exercised prior to such shareholder approval, and any Bonus Stock awarded shall
be forfeited if such shareholder approval is not obtained.

15.   TERM OF THE PLAN

      Unless sooner terminated by the Board pursuant to Article 12, the Plan
shall terminate on December 6, 2003, and no Options or Bonus Stock may be
granted after termination. The termination shall not affect the validity of any
Options or Bonus Stock may be granted after termination. The termination shall
not affect the validity of any Option or Bonus stock outstanding on the date of
termination.

16.   INDEMNIFICATION OF COMMITTEE

      In addition to such other rights of indemnification as they may have as
Directors or as members of the Committee, the members of the Committee shall be
indemnified by the Corporation against the reasonable expenses, including
attorneys' fees, actually and reasonably incurred in connection with the defense
of any action, suit or proceeding, or in connection with any appeal therein, to
which they or any of them may be a party by reason of any action taken or
failure to act under or in connection with the Plan or any Option or Bonus Stock
granted or awarded hereunder, and against all amounts reasonably paid by them in
settlement thereof or paid by them in satisfaction or judgment in any such
action, suit or proceeding, if such members acted in good faith and in a manner
which they believed to be in, and not opposed to, the best interests of the
Corporation.

17.   GENERAL PROVISIONS

      A.   The establishment of the Plan shall not confer upon any Employee any
           legal or equitable right against the Corporation, any Subsidiary or
           the Committee, except as expressly provided in the Plan.

      B.   The Plan does not constitute inducement or consideration for the
           employment of any Employee, nor is it a contract between the
           Corporation or a Subsidiary and any Employee. Participation in the
           Plan shall not give an Employee any right to be retained in the
           service of the Corporation or Subsidiary.

      C.   The Corporation and is Subsidiaries may assume options, warrants, or
           rights to purchase stock issued or granted by other corporations
           whose stock or assets shall be acquired by the Corporation or a
           Subsidiary, or

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          which shall be merged into or consolidated with the Corporation or a
          Subsidiary. Neither the adoption of this Plan, nor its submission to
          the shareholders, shall be taken to impose any limitations on the
          powers of the Corporation or its affiliates to issue, grant, or
          assume options, warrants, rights, or bonus stock, otherwise than
          under this Plan, or to adopt other stock option stock or bonus
          stock plans or to impose any requirement of shareholder approval
          upon the same.

     D.   The interests of any Employee under the Plan are not subject to the
          claims of creditors and may not, in any way, be assigned, alienated or
          encumbered except as provided in Article 8.

     E.   The Plan and each Agreement shall be governed, construed and
          administered in accordance with the laws of the State of Delaware.

     F.   The adoption of the Plan, the grant and exercise of Options and the
          award of Bonus Stock shall be subject to receipt of all required
          regulatory approvals, including without limitation any required
          approvals of the Federal Communications Commission.

     G.   Should any provision of the Plan that is intended to comply with the
          provisions of Rule 16b-3 under the Exchange Act at the date of the
          adoption of the Plan by the Board not be necessary for such
          compliance, or become no longer necessary for such compliance, such
          provision of the Plan shall have no force or effect under the Plan as
          of the date that such provision is not required for purpose of
          satisfying the provisions of Rule 16b-3 under the Exchange Act.

                                       11<PAGE>   1
                                                                   EXHIBIT 10.6a

                          [AMERICAN MOBILE LETTERHEAD]

OPTIONEE:                                                   OPTION NO.

DATE OF GRANT                                               OPTION PRICE:
COVERED SHARES

                     AMERICAN MOBILE SATELLITE CORPORATION
                                STOCK AWARD PLAN

                      NONSTATUTORY STOCK OPTION AGREEMENT

1.   Definitions. In this Agreement, terms with initial capitals shall have the
meanings provided in the Plan, except as follows:

     (a)  "Agreement" means this Nonstatutory Stock Option Agreement.

     (b)  A "Change of Control" shall be deemed to have occurred if (i) any
person or group of persons (as defined in Section 13(d) and 14(d) of the
Exchange Act) together with its affiliates, excluding employee benefit plans of
the Corporation, is or becomes, directly or indirectly, the "beneficial owner"
(as defined in Rule 13d-3 under the Exchange Act) of securities of the
Corporation representing 40% or more of the combined voting power of the
Corporation's then outstanding securities; or (ii) individuals who at the
beginning of any two-year period constitute the Board, plus new directors of the
Corporation whose election or nomination for election by the Corporation's
shareholders is approved by a vote of at least two-thirds of the directors of
the Corporation still in office who were directors of the Corporation at the
beginning of such two-year period, cease for any reason during such two-year
period to constitute at least two-thirds of the members of the Board; or
(iii) the shareholders of the Corporation approve a merger or consolidation of
the Corporation with any other corporation or entity regardless of which entity
is the survivor, other than a merger or consolidation which would result in the
voting securities of the Corporation outstanding immediately prior thereto
continuing to represent (either by remaining outstanding or being converted into
voting securities of the surviving entity) at least 80% of the combined voting
power of the voting securities of the Corporation or such surviving entity
outstanding immediately after such merger or consolidation; or (iv) the
shareholders of the Corporation approve a plan of complete liquidation or
winding-up of the Corporation or an agreement for the sale or disposition by the
Corporation of all or substantially all of the Corporation's assets.

     (c)  "Covered Shares" means the Shares subject to the Option set forth as
the "Covered Shares" on page 1 of this Agreement.

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     (d)  "Date of Exercise" means the date on which the Company receives notice
pursuant to Paragraph 4(a) of the exercise, in whole or in part, of the Option.

     (e)  "Date of Expiration" means, subject to the provisions of Section 3 of
this Agreement, ten (10) years after the Date of Grant.

     (f)  "Date of Grant" means the date set forth as the "Date of Grant" on
page 1 of this Agreement.

     (g)  "Disability" means permanent and total disability of the Optionee.

     (h)  "Equivalent Option" means, in connection with a Change of Control, a
continuation of the Option by the Corporation, an agreement by the person or
persons acquiring the Corporation to honor or assume the Option following the
Change of Control, or the substitution of a new Option with an inherent value
equivalent to that of the original Option and on terms at least as beneficial to
the Optionee as those contained in the Optionee's original Option Agreement.

     (i)  "Insider" means an Optionee or Grantee who is subject to the reporting
requirements under Section 16(a) of the Exchange Act.

     (j)  "Involuntary Termination" means termination by the Corporation or a
Subsidiary of the Optionee's employment with the Corporation or a Subsidiary or,
in connection with or following a Change of Control, a substantial reduction by
the Corporation or Subsidiary in the salary, benefits or position of the
Optionee, but does not include any such substantial reduction as a result of the
commission of a felony by the Optionee or Termination for Good Cause.

     (k)  "Option" means the nonstatutory stock option granted to the Optionee
in Paragraph 2 of this Agreement.

     (l)  "Option Period" means the period during which the Option may be
exercised.

     (m)  "Option Price" means the dollar amount per Share set forth as the
"Option Price" on page 1 of this Agreement.

     (n)  "Optionee" means the person identified as the "Optionee" on page 1 of
this Agreement.

     (o)  "Plan" means the American Mobile Satellite Corporation Stock Award
Plan, amended and restated January 27, 2000.

     (p)  "Retirement" means termination of employment with the Corporation or a
Subsidiary at age 65 or thereafter, or at such other age as provided by
Corporation policy.

     (q)  "Termination for Good Cause" means termination as a result of the
commission of a felony by the Optionee.

2.  Grant of Option. Pursuant to the Plan and subject to the terms of this
Agreement, the Corporation hereby grants to the Optionee or his successors the
Option to purchase from the Corporation that number of shares of Common Stock
equal to the Covered Shares, exercisable at the Option Price.

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3.   Terms of the Option.

     (a)  Type of Option. The Option is intended to be a nonstatutory stock
     option, and is not intended to be an incentive stock option under section
     422 of the Code.

     (b)  Option Period. During the period commencing on the Date of Grant and
     terminating on the Date of Expiration, the Option may be exercised with
     respect to all or a portion of the Covered Shares (in full shares), to the
     extent that the Option has not been previously exercised with respect to
     such Covered Shares, subject to the following limitations:

          no portion of the Option may be exercised during the first year
          following the Date of Grant;

          during the second year following the Date of Grant, the Option may be
          exercised to a maximum of 33 1/3% of the Covered Shares;

          during the third year following the Date of Grant, the Option may be
          exercised to a cumulative maximum of 66 2/3% of the Covered Shares;

          thereafter the Option may be exercised in full.

     (c)  Exercise after termination of employment: Except as provided in
     paragraphs (d) and (e) of this Section 3, if the Optionee's employment is
     terminated during the Option Period, the Option may be exercised for a
     period of six (6) months after termination in the event of an Involuntary
     Termination or for a period of three (3) months after termination in the
     case of a voluntary termination, and the Option Period shall expire at the
     end of such six (6) month period or three (3) month period, respectively.
     An Option will terminate immediately, and may no longer be exercised, in
     the event of a Termination for Good Cause.

     (d)  Exercise in the event of Death, Disability or Retirement: If the
     Optionee's employment is terminated during the Option Period in the event
     of death, Disability or Retirement, the Option may be exercised in whole or
     in part, by the Optionee, the authorized representative of the Optionee's
     estate or by his properly appointed attorney-in-fact, guardian, trustee, or
     conservator, for a period of one year after the Optionee's death,
     Disability or Retirement.

     (e)  Limitation on exercise after termination: No portion of an Option
     which is unexercisable at the termination of the Optionee's employment may
     thereafter be exercised under this Section 3 except that an Option may be
     exercised in full upon termination of other Optionee's employment with the
     Corporation or a Subsidiary by reason of the Optionee's death or Disability
     (other than Disability during the six-month period following the Date of
     Grant).

     (f)  Change of Control. Notwithstanding the provisions of Section 3(b), if
     a Change of Control occurs during the period commencing on the Date of
     Grant and terminating on the Date of Expiration, the Optionee shall be
     entitled to receive an Equivalent Option. If, despite the best efforts of
     the Corporation, the Optionee cannot receive an Equivalent Option in
     connection with such Change of Control, (i) the Optionee shall be entitled
     to receive immediately prior to such Change of Control, and in exchange for
     his or her Option, cash in an amount equal to the excess of the highest
     price paid for a Share in connection with the

<PAGE>   4
    Change of Control over the Option Price, multiplied by the total number
    of Covered Shares subject to the Option, including all of the Covered Shares
    with respect to which the Option has not yet become exercisable under the
    provisions of Section 3(b) but excluding any of the Covered Shares with
    respect to which the Option has been previously exercised, or (ii) if the
    Optionee is an Insider who would be subject to suit under Section 16(b) of
    the Exchange Act if the Optionee were to receive the cash payment described
    in Section 3(c)(i), the Option may be exercised in full beginning on the
    date two weeks before such Change of Control. If the Optionee receives an
    Equivalent Option in connection with a Change of Control, and the Optionee's
    employment with the Corporation or a Subsidiary is terminated within two
    years following the Change of Control by reason of Involuntary Termination,
    the Equivalent Option may be exercised in full beginning on the date of such
    termination if and for such period as the Committee, in its sole discretion,
    so determines.

    (g)   Other Terms of Option. Notwithstanding the provisions of Section 7.B
    of the Plan, no Shares may be used to pay any portion of the Option Price
    unless those Shares shall have been held by the Optionee for a period of not
    less than six months prior to the Date of Exercise, provided that the
    holding period may be extended by the Committee at any time or times, by
    written notice to the Optionee, to any other holding period not exceeding
    two years prior to the Date of Exercise.

4.  Exercise.

    (a)   Notice. Until the Committee notifies the Optionee to the contrary, the
    forms attached to this Agreement as Exhibit A shall be used to exercise the
    Option.

    (b)   Effect. The exercise, in whole or in part, of the Option shall cause a
    reduction in the number of Covered Shares equal to the number of shares of
    Common Stock with respect to which the Option is exercised.

5.  Restriction Upon Shares of Common Stock Issued Upon Exercise. By accepting
this Option, the Optionee agrees to the conditions specifically set forth in
Section 6.C of the Plan.

6.  Rights as Stockholder. The Optionee shall have no rights as a stockholder
with respect to any Shares subject to the Option until and unless a certificate
or certificates representing such Shares are issued to the Optionee pursuant to
this Agreement. Except as provided in Article 11 of the Plan, no adjustment
shall be made for dividends or other rights for which the record date is prior
to the issuance of such certificate or certificates.

7.  Employment. Neither the granting of the Option evidenced by this Agreement
nor any term or provision of this Agreement shall constitute or be evidence of
any understanding, express or implied, on the part of the Corporation or any of
its Subsidiaries to employ the Optionee for any period. Whenever reference is
made in this Agreement to the employment of the Optionee, it means employment by
the Corporation or a Subsidiary.

8.  Subject to the Plan. The Option evidenced by this Agreement and the exercise
thereof are subject to the terms and conditions of the Plan, which are
incorporated herein by reference and made a part hereof. In addition, the Option
is subject to any rules and regulations promulgated by the Committee consistent
with the terms of the Plan.

<PAGE>   5
IN WITNESS WHEREOF, the Corporation has caused this Agreement to be signed on
its behalf effective as of the Date of Grant.

ATTEST:                                    AMERICAN MOBILE SATELLITE CORPORATION

                                           By:
-----------------------------------           ----------------------------------

Accepted and agreed to as of the Date of
Grant.

-----------------------------------
Optionee
<PAGE>   6
                                   EXHIBIT A

                               EXERCISE OF OPTION

Board of Directors
American Mobile Satellite Corporation
10802 Parkridge Boulevard
Reston, Virginia  20191-5416

Gentlemen:

The undersigned, the Optionee under the Nonstatutory Stock Option Agreement
identified as Option No.        , granted pursuant to the American Mobile
                        --------
Satellite Corporation Stock Award Plan, hereby irrevocably elects to exercise
the Option granted in the Agreement to purchase shares of Common Stock of
American Mobile Satellite Corporation, par value $.01 per share, and herewith
makes payment of $       in the form of                       [cash, Common
                  ------                ----------------------
Stock, cash plus Common Stock] for the shares purchased and $        in the
                                                              ------
form of                        [cash, Common Stock, cash plus Common Stock] to
       -----------------------
cover the Corporation's withholding tax liability in respect of the purchase.
(Please complete.)

The Optionee hereby represents, warrants, and acknowledges the following:

     A.  The Optionee has received and reviewed the statutory prospectus
relating to the Stock Option Plan prior to making this election.

     B.  The certificate for such stock may be legended, for certain officers
who may be deemed affiliates of the Company, to the effect that such officers
may not reoffer or resell shares of Common Stock in a transaction which is not
registered under the Securities Act of 1933, as amended ("the Act"), except
pursuant to the Securities and Exchange Commission's Rule 144 under the Act, or
another exemption thereunder.

[Note: Shares of Common Stock being delivered in payment of all or any part of
the exercise price must be represented by certificates registered in the name of
the Optionee and duly endorsed by the Optionee and by each and every other
co-owner in whose name the shares may also be registered.)

Dated:                                       Name of Optionee:
      --------------------                                    ------------------

                                             -----------------------------------
                                             Signature of Optionee

Received by American Mobile Satellite Corporation:

By:                                                   Date:
   -----------------------------------------------         ---------------------

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