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                                                                    EXHIBIT 99.1

                                                     March 25, 2002

Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, DC  20549

Dear Sir or Madam:

The annual report on Form 10-K for the year ended December 31, 2001 (the
"Report") of Motient Corporation (the "Issuer") with which this letter is being
filed as an exhibit includes the Issuer's financial statements that were audited
by Arthur Andersen LLP ("Andersen"). Andersen has been the Issuer's auditor
since the Issuer's formation in 1988.

Andersen has represented to the Issuer that the audit with respect to the
financial statements included in the Report was subject to Andersen's quality
control system for the U.S. accounting and auditing practice to provide
reasonable assurance that the engagement was conducted in compliance with
professional standards and that there was appropriate continuity of Andersen
personnel working on audits, and availability of national office consultation to
conduct the relevant portions of the audit.

                                    Very truly yours,

                                    MOTIENT CORPORATION

                                    By:     /s/ David H. Engvall
                                            -------------------
                                            Name:  David H. Engvall
                                            Title:  Vice President, General
                                                    Counsel and Secretary

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