SC 13D/A

                               UNITED STATES
                     SECURITIES AND EXCHANGE COMMISSION
                           Washington, D.C. 20549



                               SCHEDULE 13D/A

                  Under the Securities Exchange Act of 1934
                             (Amendment No. 2)*


                    AMERICAN MOBILE SATELLITE CORPORATION
                              (Name of Issuer)

                   COMMON STOCK, $.01 PAR VALUE PER SHARE
                    ------------------------------------
                       (Title of Class of Securities)

                                 02755 R103
                                 ----------
                               (CUSIP Number)

                               CAROL FORSYTE
         MOTOROLA, INC., 1303 EAST ALGONQUIN ROAD, SCHAUMBURG, IL 60196
                               (847) 576-7646
         -------------------------------------------------------------
      (Name, Address and Telephone Number of Person Authorized to Receive
                         Notices and Communications)

                               AUGUST 3, 1999
                              ------------
          (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to
report the acquisition that is the subject of this Schedule 13D, and is
filing this schedule because of Rules 13d-1(e), 13d-1(f) or 13d-1(g), check
the following box [_].

Note: Schedules filed in paper format shall include a signed original and
five copies of the schedule, including all exhibits.  See Rule 13d-7(b) for
other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which
would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities
Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of
that section of the Act but shall be subject to all other provisions of the
Act (however, see the Notes).


CUSIP NO.  02755 R103
1.  NAME OF REPORTING PERSON
    I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON (entities only)
       Motorola, Inc.
       I.R.S. #36-1115800
2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)
       (a)
       (b)
3.  SEC USE ONLY
4.  SOURCE OF FUNDS (See Instructions)
       Not applicable
5.  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
       2(d) OR 2(e) [    ]
6.  CITIZENSHIP OR PLACE OF ORGANIZATION
       State of Incorporation:  Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY REPORTING PERSON WITH:
7.  SOLE VOTING POWER
       5,470,532
8.  SHARED VOTING POWER
       0
9.  SOLE DISPOSITIVE POWER
       5,470,532
10. SHARED DISPOSITIVE POWER
       0
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY REPORTING PERSON
       5,470,532
12. CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
       (See Instructions) [   ]
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
       13.9%
14. TYPE OF REPORTING PERSON (See Instructions)
       CO



                         AMENDMENT NO. 2 TO SCHEDULE 13D

     This Amendment No. 2 ("Amendment") relates to the shares (the
"Shares") of common stock, par value $0.01 per share, of American Mobile
Satellite Corporation, a Delaware corporation ("AMSC"). The percentage of
Shares reported in this Amendment as being beneficially owned by Motorola,
Inc. ("Motorola") is based upon the number of outstanding Shares on July
31, 1999, as identified in AMSC's Quarterly Report on Form 10-Q for the
period ended June 30, 1999.

Item 2.     Identity and Background

Item 2 is hereby amended and restated as follows:

     (a) - (c), (f)  This statement is being filed by Motorola, Inc., a
Delaware corporation ("Motorola").  Motorola's principal executive offices
are located at 1303 East Algonquin Road, Schaumburg, IL 60196. Motorola is
a global leader in providing integrated communications solutions and
embedded electronic solutions.  These include: (i) software-enhanced
wireless telephone, two-way radio, messaging and satellite communications
products and systems, as well as networking and Internet-access products,
for consumers, network operators, and commercial, government and industrial
customers; (ii) embedded semiconductor solutions for customers in the
consumer, networking and computing, transportation and wireless
communications markets; and (iii) embedded electronic systems for
automotive, communications, imaging, manufacturing systems, computer and
consumer markets.

     The names, business addresses and present principal occupations of the
directors and executive officers of Motorola are set forth in the attached
Appendix 1, which is incorporated herein by reference.  Appendix 1 also
lists the principal business of any employer that employs a director who is
not also an executive officer of Motorola. To the best of Motorola's
knowledge, all directors and executive officers of Motorola are citizens of
the United States.

     (d) - (e)  Neither Motorola nor, to the best of Motorola's knowledge,
any of the directors or executive officers listed on Appendix 1 has been,
during the last five years, (a) convicted in a criminal proceeding
(excluding traffic violations or similar misdemeanors) or (b) a party to a
civil proceeding of a judicial or administrative body of competent
jurisdiction and as a result of such proceeding was or is subject to a
judgment, decree or final order enjoining future violations of, or
prohibiting or mandating activities subject to, federal or state securities
laws or finding any violation with respect to such laws.

Item 5.     Interest in Securities of the Issuer

Item 5 is hereby amended and restated as follows:

     (a)  As of August 3, 1999, Motorola was the beneficial owner (as
defined in Rule 13d-3 under the Securities Exchange Act of 1934, as
amended) of 5,470,532 Shares (constituting 13.9 % of the total outstanding
shares of AMSC's common stock).  To the best of Motorola's knowledge, no
Shares are beneficially owned by any of its executive officers or
directors, nor do such executive officers or directors have the right to
acquire any Shares.

     (b)  Motorola has the sole power to vote or direct the vote and to
dispose or direct the disposition of the 5,470,532 Shares listed as
beneficially owned by Motorola in Item 5(a).

     (c)  Except as set forth herein (see Item 6), Motorola had no
transactions in Shares during the last 60 days.  To the best of Motorola's
knowledge, no director or executive officer listed on Appendix 1 has
engaged in any transactions in Shares during the past 60 days.

     (d)  Not applicable.

     (e)  Not applicable.

Item 6.  Contracts, Arrangements, Understandings or Relationships with
Respect to Securities of the Issuer

Item 6 is hereby amended and restated as follows:

     Pursuant to the Underwriting Agreement dated as of July 28, 1999 among
AMSC, Motorola and the Representatives (as defined therein) of the
Underwriters (as defined therein), in connection with AMSC's registered
public offering ("Offering") of 7,000,000 Shares in July 1999, Motorola
agreed, at the election of the Underwriters, to sell up to 1,050,00
additional Shares to the Underwriters at the public offering price of
$17.75 per share less the underwriting discount of $1.065 to cover over-
allotments.  The Underwriters elected to exercise in full the option to
purchase the additional 1,050,000 Shares and payment for and delivery of
these shares was made on August 3, 1999.  In addition Motorola agreed with
the Underwriters not to dispose of or hedge any of its Shares during the
period from July 28,1999 and continuing through the date 120 days from July
28, 1999, except with the prior written consent of Bear, Stearns & Co. Inc.

     See Item 4 for a description of the Purchase Agreement, the
Participation Agreement and the Registration Rights Agreement.  All
statements made in the body of this Schedule 13D and any amendment thereto
which relate to the terms of the Underwriting Agreement and the Purchase
Agreement and related agreements including the Participation Rights
Agreement and Registration Rights Agreement are qualified in their entirety
by the terms of such documents which are filed as Exhibits hereto.

     Except as set forth in this Schedule 13D and any amendment thereto, to
the best of Motorola's knowledge, no other contracts, arrangements,
understandings or relationships (legal or otherwise) exist among the
persons named in Item 2 or between such persons and any other person with
respect to any securities of AMSC, including but not limited to, the
transfer or voting of any such securities, finder's fees, joint ventures,
loan or option arrangements, puts or calls, guarantees of profits, the
division of profits or loss or the giving or withholding of proxies.

Item 7.     Materials to be Filed as Exhibits

Exhibit No.                          Description
Exhibit 4.1  Stock Purchase Agreement for the Acquisition of Motorola
ARDIS Acquisition, Inc. and Motorola ARDIS, Inc. by AMSC Acquisition
Company, Inc., a wholly-owned subsidiary of American Mobile Satellite
Corporation, dated as of December 31, 1997*

Exhibit 4.2  Amendment No. 1 dated March 31, 1998 to the Stock Purchase
Agreement for the Acquisition of Motorola ARDIS Acquisition, Inc. and
Motorola ARDIS, Inc. by AMSC Acquisition Company, Inc., a wholly-owned
subsidiary of American Mobile Satellite Corporation*

Exhibit 4.3  Participation Rights Agreement by and among Motorola,
Inc., American Mobile Satellite Corporation, and the parties listed on
Schedule attached thereto, dated as of December 31, 1997*

Exhibit 4.4  Registration Rights Agreement by and among Motorola, Inc.,
American Mobile Satellite Corporation dated as of March 31, 1998*

Exhibit 6.1  Form of Underwriting Agreement among AMSC; Motorola; Bear,
Stearns & Co. Inc.; Credit Suisse First Boston Corporation; Deutsche
Bank Securities Inc. and SoundView Technology Group, Inc. (incorporated
by reference to Exhibit 1 to Amendment No. 2 to AMSC's Registration
Statement on Form S-3 dated July 26, 1999 (Registration Statement No.
333-81459))

*These exhibits were previously filed as exhibits and are not being refiled
with this report.


After reasonable inquiry and to the best of our knowledge and belief, we
certify that the information set forth in this statement is true, complete
and correct.

                                   Motorola, Inc.



                                   By:  /s/ Carl F. Koenemann
                                        Name:  Carl F. Koenemann
                                        Title: Executive Vice President
                                               & Chief Financial Officer





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EX-1

                               APPENDIX 1

INFORMATION CONCERNING THE DIRECTORS AND EXECUTIVE OFFICERS OF MOTOROLA

     The following table sets forth the name, business address, and
principal occupation or employment at the present time for each
director and executive officer of Motorola. Unless otherwise noted,
each such person is a citizen of the United States. In addition, unless
otherwise noted, each such person's business address is 1303 East
Algonquin Road, Schaumburg, Illinois 60196.

DIRECTORS OF MOTOROLA, INC.


Gary L. Tooker....Vice Chairman of the Board of Directors of Motorola,
Inc.

Christopher B. Galvin....Chairman of the Board and Chief Executive
Officer, Motorola, Inc. since June 1999.

Robert W. Galvin....Chairman of the Executive Committee, Motorola, Inc.

Robert L. Growney....President and Chief Operating Officer, Motorola,
Inc.

Ronnie C. Chan....Chairman, Hang Lung Development Group. His business
address is: Hang Lung Development Company Limited, 28/F Standard
Chartered Bank Building, 4 Des Voeux Road Central, Hong Kong.

H. Laurance Fuller....Co-Chairman, BP Amoco, p.l.c. His business
address is: BP Amoco, p.l.c., 200 East Randolph Street, Chicago, IL
60601.

Anne P. Jones....Consultant. Her business address is: 5716 Bent Branch
Road, Bethesda, MD 20816.

Donald R. Jones....Retired; formerly Chief Financial Officer, Motorola,
Inc. His business address is: 1776 Beaver Pond Road, Inverness, IL
60067.

Judy C. Lewent....Senior Vice President and Chief Financial Officer,
Merck & Co., Inc. Her business address is: Merck & Co., Inc., One Merck
Drive, Whitehouse Station, NJ 08889.

Dr. Walter E. Massey....President of Morehouse College. His business
address is: Morehouse College, 830 Westview Drive, SW, Atlanta, GA
30314.

Nicholas Negroponte....Director of Media Laboratory of Massachusetts
Institute of Technology. His business address is: Massachusetts
Institute of Technology Media Lab, 20 Ames St. E15-210, Cambridge, MA
02139.

John E. Pepper, Jr....Chairman of the Board, Procter & Gamble Co. His
business address is: Procter & Gamble Co., One Procter & Gamble Plaza,
Cincinnati, OH 45202.

Samuel C. Scott III....President and Chief Operating Officer, Corn
Products International. His business address is: CPC International,
Inc. 6500 Archer Road, Summit-Argo, IL 60501.

B. Kenneth West....Senior Consultant for Corporate Governance to
Teachers Insurance and Annuity Association-College Retirement Equities
Fund. His business address is: Harris Bankcorp, Inc. P.O. Box 775,
Chicago, IL 60609.

Dr. John A. White....Chancellor, University of Arkansas. His business
address is: University of Arkansas, 425 Administration Building,
Fayetteville, AR 72701.



EXECUTIVE OFFICERS OF MOTOROLA (WHO ARE NOT ALSO DIRECTORS OF MOTOROLA)

Keith J. Bane....Executive Vice President and President, Americas
Region.
Robert L. Barnett....Executive Vice President and President,
Commercial, Government and Industrial Solutions Sector, Communications
Enterprise.
Arnold S. Brenner....Executive Vice President and President, Global
Government Relations and Standards.
Glenn A. Gienko....Executive Vice President and Motorola Director of
Human Resources.
Merle L. Gilmore....Executive Vice President and President,
Communications Enterprise.
Joseph M. Guglielmi....Executive Vice President and President,
Integrated Electronic Systems Sector.
Bo Hedfors....Executive Vice President and President, Network Solutions
Sector, Communications Enterprise.
Carl F. Koenemann....Executive Vice President and Chief Financial
Officer.
Ferdinand C. Kuznik....Executive Vice President and Presdient, Motorola
Europe, Middle East, and Africa.
A. Peter Lawson....Executive Vice President, General Counsel and
Secretary.
James A. Norling....Executive Vice President and President, Personal
Communications Sector, Communications Enterprise and Deputy to the
Chief Executive Office.
Hector Ruiz....Executive Vice President and President, Semiconductor
Products Sector.
C. D. Tam....Executive Vice President and President, Asia Pacific
Region.
Frederick T. Tucker....Executive Vice President and Deputy to the Chief
Executive Office.
Richard W. Younts....Executive Vice President and Senior Advisor on
Asian Affairs.