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                                                                   EXHIBIT 10.28
                                PLEDGE AGREEMENT

THIS SHARE PLEDGE AGREEMENT is entered into as of this 27th day of January,
2003, between M&E Advisors L.L.C., as collateral agent for the Secured Parties
(in such capacity, together with any successor in such capacity, the "Collateral
Agent") and Motient Holdings Inc. (the "Pledgor").

WHEREAS, the Pledgor, Motient Communications Inc., Motient Corporation and the
Secured Parties have entered into a $12,500,000 Amended and Restated Term Credit
Agreement (the "Loan Agreement") dated as of January 27, 2003, pursuant to which
the Borrower has agreed to borrow from the Secured Parties, and the Secured
Parties have agreed to lend to the Borrower, certain amounts, all in accordance
with and subject to the terms and conditions set forth in the Loan Agreement;

WHEREAS, pursuant to the Loan Agreement, the Borrower has executed and delivered
a promissory note evidencing the indebtedness under the Loan Agreement to each
of the Secured Parties (each, a "Note" and together, the "Notes") of even date
herewith;

WHEREAS, to induce the Secured Parties to enter into the Loan Agreement, and for
other good and valuable consideration the receipt and sufficiency of which are
hereby acknowledged, the Pledgor has agreed to enter into this Agreement and to
grant to the Secured Parties a security interest in the Collateral (as
hereinafter defined) to secure the full and punctual performance of the Secured
Obligations (as hereinafter defined);

WHEREAS, capitalized terms used herein and not otherwise defined herein shall
have the meanings set forth in the Loan Agreement;

NOW, THEREFORE, in consideration of the foregoing and of the mutual covenants
and agreements hereinafter set forth, the parties hereto agree as follows:

                                    ARTICLE 1
                                SECURITY INTEREST

     Section 1.01. The Pledge. As security for the prompt payment in full when
due (whether at stated maturity, by acceleration or otherwise) of the Secured
Obligations, whether now existing or hereafter from time to time arising, the
Pledgor hereby pledges and grants to the Collateral Agent, for the benefit of
the Secured Parties a Security Interest in and lien on all of the Pledgor's
right, title and interest in, to and under the following property, whether now
owned or hereafter acquired or hereafter coming into existence and wherever
located (all being collectively referred to herein as the "Collateral"):

                           (a) all Pledged Shares, together with, in each case:

                                    (i) all shares, securities, moneys or
                           property representing a dividend on any of the
                           Pledged Shares, or representing a distribution or
                           return of capital upon or in respect of the Pledged
                           Shares, or resulting from a split-up, revision,


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                           reclassification or other like change of the Pledged
                           Shares or otherwise received in exchange therefor,
                           and any subscription warrants, rights or options
                           issued to the holders of, or otherwise in respect of,
                           the Pledged Shares,

                                    (ii) without affecting the obligations of
                           the Pledgor under any provision prohibiting such
                           action hereunder or under the Loan Agreement, in the
                           event of any consolidation or merger in which the
                           Pledgor is not the surviving corporation, all shares
                           of each class of capital stock of the successor
                           corporation (unless such successor corporation is the
                           Pledgor itself) formed by or resulting from such
                           consolidation or merger; and

                                    (iii) all Proceeds of and to any of the
                           property of the Pledgor described in the preceding
                           clauses of this Section 1.01 (including, without
                           limitation, all causes of action, claims and
                           warranties now or hereafter held by the Pledgor with
                           respect to any of the items listed above) and, to the
                           extent related to any property described in said
                           clauses or such proceeds, all books, correspondence,
                           credit files, records, invoices and other papers;

     Section 1.02. Financing Statements. Prior to or concurrently with the
execution and delivery of this Agreement, the Pledgor will promptly join with
the Collateral Agent in executing financing statements, continuation statements,
assignments, certificates and other documents with respect to the Collateral
pursuant to the Uniform Commercial Code, any other applicable law and otherwise
as may be necessary or appropriate (in the reasonable judgment of the Collateral
Agent) to enable the Collateral Agent to create, preserve, perfect or from time
to time renew the security interests granted hereby, in form satisfactory to the
Collateral Agent, and the Pledgor will pay the cost of filing the same in all
public offices wherever the Collateral Agent deems filing to be necessary or
appropriate (in the reasonable judgment of the Collateral Agent). The Pledgor
grants the Collateral Agent the right, at the Collateral Agent's option, to file
any or all such financing statements, continuation statements and other
documents pursuant to the Uniform Commercial Code, any other applicable law or
otherwise, without the Pledgor's signature, and irrevocably appoints the
Collateral Agent as attorney in fact for the Pledgor to execute any such
statements and documents in the Pledgor's name and to perform all other acts
which the Collateral Agent deems appropriate to perfect and continue the
security interests conferred by this Agreement. The Pledgor authorizes the
Collateral Agent to file one or more Uniform Commercial Code financing
statements or continuation statements relating to all or any part of the
Collateral without the signature of the Pledgor where permitted by law. The
Collateral Agent may, at any time and from time to time, pursuant to the
provisions of this Section 1.02, file financing statements that describe the
Collateral as all assets and/or all personal property of the Pledgor or words of
similar effect and which contain any other information required by Part 5 of
Revised Article 9 of the Uniform Commercial Code for the sufficiency or filing
office acceptance of any financing statement, including whether the Pledgor is
an organization, the type of organization and any organization identification
number issued to the Pledgor. The Pledgor agrees to promptly furnish any such
information to the Collateral Agent upon request. Any such financing statements
may be signed by the Collateral Agent on behalf of the Pledgor and may be filed
at any time in any jurisdiction whether or not Revised Article 9 is then in
effect in that jurisdiction.

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     Section 1.03. Share Certificates. Prior to or concurrently with the
execution of this Agreement, the Pledgor will deliver to the Collateral Agent
certificates representing the Pledged Shares and such certificates shall be duly
endorsed in blank or accompanied by stock powers duly executed by the Pledgor in
blank, together with any documentary tax stamps and any other documents
necessary or desirable to cause the Collateral Agent to have a good, valid and
perfected first pledge of, lien on and security interest in the Share
Collateral, free and clear of any mortgage, pledge, lien, security interest,
hypothecation, assignment, charge, right, encumbrance or restriction other than
those arising under federal or state Securities laws.

     Section 1.04. Preservation of Rights. The Collateral Agent shall not be
required to take steps necessary to preserve any rights against prior parties to
any of the Collateral.

                                    ARTICLE 2
                    REPRESENTATIONS AND WARRANTIES OF PLEDGOR

The Pledgor hereby represents and warrants to the Secured Parties that:

     Section 2.01. Title to Collateral. As of the date hereof, the Pledgor is
the sole beneficial owner of, and has good, valid and marketable title to, the
Collateral in which it purports to grant a security interest pursuant to Section
1.01, free from all Liens, except for Permitted Liens and except for the
Security Interests in favor of the Collateral Agent for the benefit of the
Secured Parties created or provided for herein, and has full right and power to
grant the Secured Parties a Security Interest therein. Upon the execution and
delivery of this Agreement, and upon the filing of financing statements referred
to in Section 1.02 hereof, the Secured Parties will have a good, valid and
perfected first lien and Security Interest in the Collateral, subject to no
equal or prior Liens, encumbrances or security interests in favor of any other
person or entity, except Permitted Liens.

     Section 2.02. Pledged Shares. The Pledged Shares will be duly authorized,
validly existing, fully paid and non-assessable and none of such Pledged Shares
are or will be subject to any contractual restriction, or any restriction under
the charter or by-laws of the respective issuer of such Pledged Shares, upon the
transfer of such Pledged Shares (except for any such restriction contained
herein or in the Loan Agreement or arising under federal or state securities
laws). The Pledged Shares constitute all of the issued and outstanding shares of
capital stock of any class of the Motient Communications Inc. and Motient
Services Inc. beneficially owned by the Pledgor on the date hereof (whether or
not registered in the name of the Pledgor) and Exhibit A correctly identifies,
as of the date hereof, the respective issuers of such Pledged Shares, the
respective class and par value of the shares constituting such Pledged Shares
and the respective number of shares (and registered owners thereof) represented
by each such certificate.

     Section 2.03. Names, Etc.

 The full and correct legal name, type of organization, jurisdiction of
organization, organizational ID number (if applicable) and mailing address of
the Pledgor as of the date hereof are correctly set forth in Exhibit B.

     Section 2.04. Changes in Circumstances. The Pledgor has not (i) within the
period of four months prior to the date hereof, changed its location (as defined

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in Section 9-307 of the Uniform Commercial Code), (ii) heretofore changed its
name, or (iii) heretofore become a "new debtor" (as defined in Section
9-102(a)(56) of the Uniform Commercial Code) with respect to a currently
effective security agreement previously entered into by any other Person.

     Section 2.05. Financing Statements. No Financing Statement (other than any
which may have been filed on behalf of the Secured Parties) relating to any of
the Collateral is on file in any public office.

     Section 2.06. Non-Subordination. The obligations of the Pledgor under this
Agreement are not subordinated in any way to any other obligation of the Pledgor
or to the rights of others.

     Section 2.07. True at Closing Date. Each of the representations and
warranties set forth in this Agreement or any other Loan Document shall be true
and correct as of the Closing Date with the same effect as though such
representation and warranty had been made on and as of the Closing Date.

                                    ARTICLE 3
                        AFFIRMATIVE COVENANTS OF PLEDGOR

Until all Secured Obligations of the Pledgor have been paid in full and
performed, the Pledgor hereby covenants that it shall, unless the Collateral
Agent otherwise consents in advance in writing:

     Section 3.01. Change in Places of Business or Chief Executive Office.
Maintain its location (as defined in Section 9-307 of the Uniform Commercial
Code) only at the location set forth in Exhibit B attached hereto, provided that
it shall provide to the Collateral Agent at least thirty (30) days' prior
written notice of any changes in location (as defined in Section 9-307 of the
Uniform Commercial Code).

     Section 3.02. Delivery and Other Perfection. The Pledgor shall:


                  (a) if any of the shares, securities, moneys or property
         required to be pledged by the Pledgor under Article 1 are received by
         the Pledgor, then the Pledgor shall forthwith either (x) transfer and
         deliver to the Collateral Agent such shares or securities so received
         by the Pledgor (together with the certificates for any such shares and
         securities duly endorsed in blank or accompanied by undated stock
         powers duly executed in blank), all of which thereafter shall be held
         by the Collateral Agent, pursuant to the terms of this Agreement, as
         part of the Collateral or (y) take such other action as the Collateral
         Agent shall deem reasonably necessary or appropriate to duly record the
         Lien created hereunder in such shares, securities, moneys or property
         in said Section 1.01;

                  (b) give, execute, deliver, file, record, authorize or obtain
         all such financing statements, notices, instruments, documents,
         agreements, consents or other papers as may be necessary or desirable
         (in the reasonable judgment of the Collateral Agent) to create,
         preserve, perfect or validate the security interest granted pursuant
         hereto or to enable the Collateral Agent to exercise and enforce their
         rights hereunder with respect to such pledge and security interest;
         including, without limitation, causing any or all of the Share

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         Collateral to be transferred of record into the name of the Collateral
         Agent or its nominee (and the Collateral Agent agrees that if any Share
         Collateral is transferred into its name or the name of its nominee, the
         Collateral Agent will thereafter promptly give to the Pledgor copies of
         any notices and communications received by it with respect to the Share
         Collateral pledge by the Pledgor hereunder), provided that notices to
         account debtors in respect of any Accounts, Chattel Paper or General
         Intangibles and to obligors on Instruments shall be subject to the
         provisions of clause (d) below;

                  (c) keep full and accurate books and records relating to the
         Collateral, and stamp or otherwise mark such books and records in such
         manner as the Collateral Agent may reasonably require in order to
         reflect the security interests granted by this Agreement; and

                  (d) permit representatives of the Collateral Agent, upon
         reasonable notice, at any time during normal business hours to inspect
         and make abstracts from its books and records pertaining to the
         Collateral, and permit representatives of the Collateral Agent to be
         present at the Pledgor's place of business to receive copies of all
         communications and remittances relating to the Collateral, and forward
         copies of any notices or communications received by the Pledgor with
         respect to the Collateral, all in such manner as the Collateral Agent
         may reasonably require.

     Section 3.03. Notice of Default and Loss. Provide to the Collateral Agent
written notice of any Event of Default and of any loss or damage to the
Collateral, however occasioned, immediately upon the occurrence of such Event of
Default or loss or damage.

     Section 3.04. Collateral.

(a) the Pledgor will cause the Share Collateral to constitute at all times 100%
of the total number of shares of each class of capital stock of each Issuer then
outstanding.

(b) So long as no Event of Default shall have occurred and be continuing, the
Pledgor shall have the right to exercise all voting, consensual and other powers
of ownership pertaining to the Share Collateral for all purposes not
inconsistent with the terms of this Agreement, the Loan Agreement or any other
Loan Document or other instrument or agreement referred to herein or therein,
provided that the Pledgor agrees that it will not vote the Share Collateral in
any manner that is inconsistent with the terms of this Agreement, the Loan
Agreement or any such other Loan Document or other instrument or agreement; and
the Collateral Agent shall execute and deliver to the Pledgor or cause to be
executed and delivered to the Pledgor all such proxies, powers of attorney,
dividend and other orders, and all such instruments, without recourse, as the
Pledgor may reasonably request for the purpose of enabling the Pledgor to
exercise the rights and powers that it are entitled to exercise pursuant to this
Section 3.04.

(c) Unless and until an Event of Default has occurred and is continuing, the
Pledgor shall be entitled to receive and retain any and all dividends and
distributions on the Share Collateral.

     Section 3.05. Further Assurances. From time to time, upon the written
request of the Collateral Agent, execute and deliver such further documents and
do such other acts and things as the Collateral Agent may reasonably request in
order to fully effect the purposes of this Agreement.

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                                    ARTICLE 4
                          NEGATIVE COVENANTS OF PLEDGOR

Until all Secured Obligations of the Pledgor are paid in full and performed, the
Pledgor hereby covenants and agrees that it shall not, unless the Collateral
Agent otherwise consent in advance in writing:

     Section 4.01. Other Agreements. Enter into any agreement or undertaking
containing any provision which would be violated or breached by the Pledgor's
performance of its obligations under this Agreement.

     Section 4.02. Other Financing Statements and Liens. Without the prior
written consent of the Collateral Agent (a) file or suffer to be on file, or
authorize or permit to be filed or to be on file, in any jurisdiction, any
financing statement or like instrument with respect to any of the Collateral in
which the Collateral Agent are not named as the sole secured party for the
benefit of the Secured Parties, or (b) cause or permit any Person other than the
Collateral Agent to have "control" (as defined in Section 9-104, 9-105, 9-106 or
9-107 of the Uniform Commercial Code) of any Deposit Account, Electronic Chattel
Paper, Investment Property or Letter-of-Credit Right constituting part of the
Collateral.

                                    ARTICLE 5
                                EVENTS OF DEFAULT

The Pledgor shall be in default under this Agreement upon the happening of any
of the following events or conditions ("Events of Default"):

     Section 5.01. Representation and Warranties. Any representation or warranty
of the Pledgor made herein or in any other Loan Document shall prove to have
been incorrect or misleading or breached in any material respect on or as of any
date as of which made; or

     Section 5.02. Observance of Covenants. The Pledgor shall at any time fail
to observe, satisfy or perform any of the covenants or agreements contained in
Article 3 or 4 hereof or fail to comply with any other provision contained
herein and such default shall continue unremedied for a period of twenty (20)
Business Days after written notice of the existence of such default shall have
been received by the Pledgor from the Collateral Agent; or

     Section 5.03. Event of Default under Loan Agreement. An Event of Default
under the Loan Agreement or any other Loan Document shall occur.

                                    ARTICLE 6
                   RIGHTS UPON OCCURRENCE OF EVENTS OF DEFAULT

     Section 6.01. Rights of the Collateral Agent. Upon the occurrence and
continuance of any Event of Default, the Collateral Agent shall have the right


<PAGE>

                  (a) to declare all of the Secured Obligations to be
         immediately due and payable, whereupon all such Secured Obligations
         shall become immediately due and payable without presentment, demand,
         protest or further notice of any kind, all of which are hereby
         expressly waived by the Pledgor, anything contained herein to the
         contrary notwithstanding;

                  (b) to exercise any one or more of the rights and remedies
         exercisable by the Collateral Agent under other provisions of this
         Agreement or exercisable by a secured party under the Uniform
         Commercial Code as in effect in New York (whether or not said Uniform
         Commercial Code is in effect in the jurisdiction where the rights and
         remedies are asserted) or under any other applicable law;

                  (c) to exercise, in the name of the Pledgor or in the name of
         the Collateral Agent, such rights and powers with respect to the
         Collateral as the Pledgor might exercise, including the right to
         demand, sue, collect or receive any money or property at any time
         payable or receivable on account of or in exchange for any of the
         Collateral;

                  (d) whether or not the Collateral Agent or any Secured Party
         exercises any available right to declare any Secured Obligation due and
         payable or seek or pursue any other relief or remedy available to it
         under applicable law or under this Agreement, the Loan Agreement or any
         other Loan Document or other instrument or agreement relating to such
         Secured Obligation, (a) any and all Pledged Shares will be, at the
         option of the Collateral Agent, registered on the books of the relevant
         company in the name of the Collateral Agent and (b) all dividends and
         other distributions on the Share Collateral shall be paid directly to
         the Collateral Agent and retained by it on behalf of the Secured
         Parties as part of the Share Collateral, subject to the terms of this
         Agreement, and, if the Collateral Agent shall so request in writing,
         the Pledgor agrees to execute and deliver to the Collateral Agent
         appropriate additional dividend, distribution and other orders and
         documents to that end, provided that if such Event of Default is cured,
         any such dividend or distribution theretofore paid to the Collateral
         Agent shall, upon request of the Pledgor (except to the extent
         theretofore applied to the Secured Obligations), be returned by the
         Collateral Agent to the Pledgor; and

                  (e) to sell, lease, assign or otherwise dispose of all or a
         part of the Collateral that shall then be or shall thereafter come into
         the possession, custody or control of the Collateral Agent at such
         place or places that the Collateral Agent deems best, and for cash or
         for credit or for future delivery (without thereby assuming any credit
         risk), at public or private sale, without demand of performance or
         notice of intention to effect any such disposition or of the time or
         place thereof (except such notice as required below or by applicable
         statute and cannot be waived), and the Collateral Agent, any Secured
         Party or anyone else may be the purchaser, lessee, assignee or
         recipient of any or all of the Collateral so disposed of at any public
         sale (or, to the extent permitted by law, at any private sale) and
         thereafter hold the same absolutely, free from any claim or right of
         whatsoever kind, including any right or equity of redemption (statutory
         or otherwise), of the Pledgor, any such demand, notice and right or
         equity being hereby expressly waived and released. Unless the
         Collateral is perishable or threatens to decline speedily in value or
         is of a type customarily sold on a recognized market, the Collateral

<PAGE>

         Agent will give the Pledgor at least five (5) days' prior written
         notice of the time and place of any public sale thereof or of the time
         after which any private sale or any other intended disposition thereof
         is to be made, which notice shall constitute reasonable notice. The
         Collateral Agent may, without notice or publication, adjourn any public
         or private sale or cause the same to be adjourned from time to time by
         announcement at the time and place fixed for the sale, and such sale
         may be made at any time or place to which the sale may be so adjourned.

The Pledgor recognizes that, by reason of certain prohibitions contained in the
Securities Act of 1933, as amended, and applicable state securities laws, the
Collateral Agent may be compelled, with respect to any sale of all or any part
of the Collateral, to limit purchasers to those who will agree, among other
things, to acquire the Collateral for their own account, for investment and not
with a view to the distribution or resale thereof. The Pledgor acknowledges that
any such private sales may be at prices and on terms less favorable to the
Collateral Agent than those obtainable through a public sale without such
restrictions, and, notwithstanding such circumstances, agree that any such
private sale shall be deemed to have been made in a commercially reasonable
manner and that the Collateral Agent shall have no obligation to engage in
public sales and no obligation to delay the sale of any Collateral for the
period of time necessary to permit the respective issuer to register it for
public sale.

     Section 6.02. Deficiency. If the Proceeds or sale, collection or other
realization of or upon the Collateral pursuant to this Article 6 are
insufficient to cover the costs and expenses or such realization and the payment
in full of the Secured Obligations, the Pledgor shall remain liable for any
deficiency.

     Section 6.03. Private Sale. The Collateral Agent shall not incur any
liability as a result of a private sale of the Collateral, or any part thereof,
at any private sale pursuant to Section 6.03 conducted in a commercially
reasonable manner. The Pledgor hereby waives any claims against the Collateral
Agent arising by reason of the fact that the price at which the Collateral may
have been sold at such a private sale was less than the price that might have
been obtained at a public sale or was less than the aggregate amount of the
Secured Obligations, even if the Collateral Agent accepts the first offer
received and does not offer the Collateral to more than one offeree, so long as
such private sale is conducted in a commercially reasonable manner.

     Section 6.04. Locations, Names. Without at least 30 days' prior written
notice to the Collateral Agent, the Pledgor shall not change its location (as
defined in Section 9-307 of the Uniform Commercial Code) or change its name from
the name shown as its current legal name on Exhibit B.

     Section 6.05. Application of Proceeds. Except as otherwise herein expressly
provided, the Proceeds of any collection, sale or other realization of all or
any part of the Collateral pursuant hereto shall be applied by the Collateral
Agent in the following order of priority:

     First, to the payment of all costs and expenses of such collection, sale or
other realization (including reasonable out-of-pocket costs and expenses of the
Secured Parties and fees and expenses of its agents and counsel, and all
expenses, liabilities and advances made or incurred in connection therewith);

<PAGE>

     Next, to the payment in full of all Secured Obligations, in each case
equally and ratably in accordance with the respective amounts thereof then due
and owing or as the Secured Parties holding the same may otherwise agree; and

     Finally, to the payment to the Pledgor or its successors and assigns,
unless otherwise provided by law or directed by a court of competent
jurisdiction.

     Section 6.06. Attorney-in-Fact. Without limiting any rights or powers
granted by this Agreement to the Collateral Agent, upon the occurrence and
during the continuance of any Event of Default the Collateral Agent is hereby
appointed the attorney-in-fact of the Pledgor for the purpose of carrying out
the provisions of this Article 6 and taking any action and executing any
instruments that the Collateral Agent may deem necessary or advisable to
accomplish the purposes hereof, which appointment as attorney-in-fact is
irrevocable and coupled with an interest. Without limiting the generality of the
foregoing, so long as the Collateral Agent shall be entitled under this Article
6 to make collections in respect of the Collateral, the Collateral Agent shall
have the right and power to receive, endorse and collect all checks made payable
to the order of the Pledgor representing any dividend, payment or other
distribution in respect of the Collateral or any part thereof and to give full
discharge for the same.

     Section 6.07. Right of the Collateral Agent To Appoint Receiver. Without
limiting any other rights granted to the Collateral Agent under this Agreement,
the Collateral Agent shall have the right to apply for and have a receiver
appointed by a court of competent jurisdiction in any action taken by the
Collateral Agent to enforce its rights and remedies hereunder in order to
manage, protect and preserve the Collateral and continue the operation of the
business of the Pledgor and to collect all revenues and profits thereof and
apply the same to the payment of all expenses and other charges of such
receivership including the compensation of the receiver and to the payments as
aforesaid until a sale or other disposition of such Collateral shall be finally
made and consummated.

                                    ARTICLE 7
                            MISCELLANEOUS PROVISIONS

     Section 7.01. Additional Actions and Documents. The Pledgor hereby agrees
to take or cause to be taken such further actions, to execute, deliver and file
or cause to be executed, delivered and filed such further documents and
instruments, and to obtain such consents, as may be necessary or as may be
reasonably requested in order to fully effectuate the purposes, terms and
conditions of this Agreement, whether before, at or after the closing of
transactions contemplated hereby or the occurrence of an Event of Default
hereunder.

     Section 7.02. Expenses. The Pledgor agrees to reimburse the Collateral
Agent and each of the Secured Parties for all reasonable costs and expenses
incurred by them (including, without limitation, the reasonable fees and
expenses of legal counsel, in connection with (a) any Event of Default and any
enforcement or collection proceeding resulting therefrom, including, without
limitation, all manner of participation in or other involvement with (i)
performance by the Collateral Agent of any obligations of the Pledgor in respect

<PAGE>

of the Collateral that the Pledgor has failed or refused to perform, (ii)
bankruptcy, insolvency, receivership, foreclosure, winding up or liquidation
proceedings, or any actual or attempted sale, or any exchange, enforcement,
collection, compromise or settlement in respect of any of the Collateral, and
for the care of the Collateral and defending or asserting rights and claims of
the Collateral Agent in respect thereof, by litigation or otherwise, including
expenses of insurance, (iii) judicial or regulatory proceedings and (iv)
workout, restructuring or other negotiations or proceedings (whether or not the
workout, restructuring or transaction contemplated thereby is consummated) and
(b) the enforcement of this Section 7.02, and all such costs and expenses shall
be Secured Obligations entitled to the benefits of the collateral security
provided pursuant to Section 1.01; provided, however, the Pledgor shall only be
required to reimburse the Collateral Agent and the Secured Parties under this
Section 7.02 for the reasonable costs, fees and expenses of one (1) legal
counsel for the Collateral Agent on behalf of the Secured Parties.

     Section 7.03. Notices. All notices, demands, requests, or other
communications which may be or are required to be given, served or sent by any
party to any other party pursuant to this Agreement shall be in writing and
shall be mailed by first-class, registered or certified mail, return receipt
requested, postage prepaid, or transmitted by telegram, addressed as follows:

                  (a)      If to the Pledgor:

                           Motient Holdings Inc.
                           10802 Parkridge Boulevard
                           Reston, Virginia  20191
                           Attention:  General Counsel

                           with a copy (which shall not constitute notice) to:

                           Hogan & Hartson L.L.P.
                           8300 Greensboro Drive
                           Suite 1100
                           McLean, Virginia  22102
                           Attention:  Richard K. A. Becker, Esq.

                  (b)      If to the Collateral Agent:

                           M&E Advisors L.L.C.
                           c/o Romulus Holdings Inc.
                           560 Sylvan Avenue
                           Englewood Cliffs, NJ  07632
                           Attention:  Gary Singer
                           Telephone:  201-568-4400 ext. 12
                           Fax:  201-568-4467

Each party may designate by notice in writing a new address to which any notice,
demand, request or communication may thereafter be so given, served or sent.
Each notice, demand, request or communication which shall be mailed in the
manner described above, or which shall be delivered to a telegraph company,
shall be deemed sufficiently given, served, sent or received for all purposes
upon receipt.

<PAGE>


     Section 7.04. Waiver of Right to Judicial Hearing. The Pledgor hereby
waives any right it may have to a judicial hearing prior to the exercise of any
right or remedy provided to the Collateral Agent under this Agreement, and
waives its rights, if any, to set aside or invalidate any sale duly consummated
in accordance with the foregoing provisions hereof on the grounds (if such be
the case) that the sale was consummated without a prior judicial hearing. The
Pledgor's waivers under this paragraph have been made voluntarily and knowingly
and after the Pledgor has been apprised and counseled by its attorneys as to the
nature of such rights and as to the Pledgor's possible alternative rights.

     Section 7.05. Waiver by the Collateral Agent. No waiver by the Collateral
Agent of, or consent by the Collateral Agent to, a variation from the
requirements of any provision of this Agreement shall be effective unless made
in a written instrument duly executed on behalf of the Collateral Agent by its
duly authorized officer, and any such waiver shall be limited solely to those
rights or conditions expressly waived. No failure on the part of the Collateral
Agent to exercise, and no course of dealing with respect to, and no delay in
exercising, any right, power or remedy hereunder shall operate as a waiver
thereof; nor shall any single or partial exercise by the Collateral Agent of any
right, power or remedy hereunder preclude any other or further exercise thereof
or the exercise of any other right, power or remedy. The remedies herein are
cumulative and are not exclusive of any remedies provided by law.

     Section 7.06. Governmental Approvals. The Collateral Agent acknowledges
that in connection with any exercise by them of their rights hereunder to
dispose of or operate under the licenses, permits, or other approvals covered
hereby, it may be necessary to obtain the prior consent or approval of certain
governmental authorities. Upon the exercise by the Collateral Agent of any
power, right, privilege or remedy pursuant to this Agreement which requires any
consent, approval, registration, qualification or authorization of any
governmental authority or instrumentality, the Pledgor will execute and deliver,
or will cause the execution and delivery of, all applications, certificates,
instruments and other documents and papers that the Collateral Agent may be
required to obtain for such governmental consent, approval, registration,
qualification or authorization.

     Section 7.07. Release of Collateral. Promptly following performance and
payment in full of the Secured Obligations, the Security Interest created hereby
shall terminate, and the Collateral Agent shall execute and deliver such
documents, at the Pledgor's expense, as are necessary to release the Collateral
Agent's Security Interest in the Collateral.

     Section 7.08. Benefit and Assignment. This Agreement shall be binding upon
and shall inure to the benefit of the Collateral Agent, the Pledgor and the
Secured Parties and their respective successors and assigns as permitted
hereunder. This Agreement may not be assigned by the Pledgor without the prior
written consent of the Collateral Agent and the Secured Parties. In the event of
a sale or assignment by the Secured Parties of all or any part of the interests
in the Notes, the Secured Parties may assign and transfer their rights and
interests under this Agreement in whole or in part to the purchaser or
purchasers of such interests in the Notes, whereupon such purchaser or
purchasers shall become vested with all of the powers and rights given to the
Secured Parties hereunder, and shall be deemed to be Secured Parties for all
purposes hereunder, and the predecessor Secured Parties shall thereafter be
forever released and fully discharged from any liability or responsibility
hereunder with respect to the rights and interests so assigned.

<PAGE>

     Section 7.09. Severability. If fulfillment of any provision of this
Agreement, or performance of any transaction related hereto, at the time such
fulfillment or performance shall be due, shall involve transcending the limit of
validity prescribed by law, then the obligation to be fulfilled or performed
shall be reduced to the limit of such validity.

     Section 7.10. Survival. It is the express intention and agreement of the
parties hereto that all covenants and agreements, statements, representations,
warranties and indemnities made by the Pledgor shall survive the execution and
delivery of this Agreement.

     Section 7.11. Rights Cumulative. The rights and remedies of the Collateral
Agent described herein are cumulative and not exclusive of any other rights or
remedies which the Collateral Agent otherwise would have at law or in equity or
otherwise. No notice to or demand on the Pledgor in any case shall entitle the
Pledgor to any other notice or demand in similar or other circumstances.

     Section 7.12. Entire Agreement, Modification. This Agreement and the
exhibits hereto constitute the entire agreement of the parties hereto with
respect to the transactions contemplated herein, and supersede all prior oral
and written agreements with respect to the transactions contemplated herein, and
may not be modified, deleted or amended in any manner except by agreement in
writing executed by the parties.

     Section 7.13. Termination. This Agreement shall continue in force until the
date on which the Secured Obligations shall have been paid and discharged in
full and the Commitments of the Secured Parties under the Loan Agreement have
terminated.

     Section 7.14. Construction. This Agreement, the rights and obligations of
the parties hereto, and any claims or disputes relating thereto, shall be
governed by and construed in accordance with the laws of New York. Each party
hereto hereby acknowledges that all parties hereto participated equally in the
negotiation and drafting of this Agreement and that, accordingly, no court
construing this Agreement shall construe it more stringently against one party
than against the other.

     Section 7.15. Pronouns. All pronouns and any variations thereof shall be
deemed to refer to the masculine, feminine, neuter, singular or plural, as the
identity of the person or entity may require.

     Section 7.16. Headings. Section and subsection headings contained in this
Agreement are inserted for convenience of reference only, shall not be deemed to
be a part of this Agreement for any purpose, and shall not in any way define or
affect the meaning, construction or scope of any of the provisions hereof.

     Section 7.17. Payments. If any payment or performance of obligations under
this Agreement becomes due on a day other than a Business Day, the due date

<PAGE>

shall be extended to the next succeeding Business Day, and interest thereon (if
applicable) shall be payable at then applicable rate during such extension.

     Section 7.18. Execution. To facilitate execution, this Agreement may be
executed in as many counterparts as may be required; and it shall not be
necessary that the signatures of, or on behalf of, each party, or that the
signatures of all persons required to bind any party, appear on each
counterpart; but it shall be sufficient that the signature of, or on behalf of,
each party, or that the signatures of the persons required to bind any party,
appear on one or more of the counterparts. All counterparts shall collectively
constitute a single agreement. It shall not be necessary in making proof of this
Agreement to produce or account for any particular number of counterparts; but
rather any number of counterparts shall be sufficient so long as those
counterparts contain the respective signatures of, or on behalf of, all of the
parties hereto.

                                    ARTICLE 8
                           DEFINITIONS AND REFERENCES

     Section 8.01. Defined Terms. As used in this Agreement, the following terms
shall have the meanings specified in this Section 8.01, unless the
context otherwise requires:

"Agreement" shall mean this Agreement, as the same from time to time may be
amended, supplemented or modified.

"Collateral" shall have the meaning assigned to that term in Section 1.01
hereof. For the avoidance of doubt, Collateral shall not include the Excluded
Property.

"Collateral Agent" shall have the meaning assigned to that term in the
introductory paragraph hereto.

"Event of Default" shall mean any of the events specified in Article 5 hereof,
provided that any requirement for the giving of notice, the lapse of time, or
both, or any other condition, has been satisfied.

"Issuers" shall mean Motient Communications Inc. and Motient Services Inc.

"Loan Agreement" shall have the meaning set forth in the recitals hereto.

"Motorola Credit Agreement" means the Credit Agreement dated as of June 17, 1998
between Motorola Inc., a Delaware corporation, and Motient Communications Inc.
(formerly known as ARDIS Company).

"Pledged Shares" shall mean all shares owned by the Pledgor and described in
Exhibit A (as such Exhibit may be amended from time to time).

"Proceeds" shall mean (i) all 'proceeds' as defined in Article 9 of the Uniform
Commercial Code as in effect in New York on the date hereof (whether or not said
Code is in effect in the jurisdiction where the rights and remedies are
asserted), (ii) payments or distributions made with respect to any Collateral
and (iii) whatever is receivable or received when Collateral or proceeds are
sold, exchanged, collected or otherwise disposed of, whether such disposition is
voluntary or involuntary.

<PAGE>


"Secured Obligations" shall mean, collectively, all Obligations of every nature
of the Pledgor from time to time owed to the Secured Parties under the Loan
Documents including (a) all principal of and interest (including, without
limitation, any interest which accrues after the commencement of any case,
proceeding or other action relating to the bankruptcy, insolvency or
reorganization of the Pledgor, whether or not allowed or allowable as a claim in
any such proceeding) on any Loans under, or Note issued pursuant to, the Loan
Agreement, (b) all other amounts payable by the Pledgor hereunder or under any
other Loan Document and (c) any renewals or extensions of any of the foregoing.

"Secured Party" or "Secured Parties" shall mean any Lender or the Lenders party
to the Loan Agreement, as the case may be.

"Security Interest" means an interest in property which secures payment or
performance of an obligation.

     Section 8.02. Other Definitional Provisions.

(a) All terms defined in this Agreement shall have the defined meanings provided
herein when used in the Loan Documents.

(b) As used herein and in the Loan Documents, accounting terms not defined in
Section 8.01 hereof, and accounting terms partly defined in Section 8.01 hereof
to the extent not defined, shall have the respective meanings given to them
under generally accepted accounting principles in effect on the date hereof and
consistently applied.

(c) The words "hereof," "herein" and "hereunder" and words of similar import
when used in this Agreement shall refer to this Agreement as a whole and not to
any particular provision of this Agreement.



<PAGE>


IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to be
duly executed and delivered in its name and on its behalf, all as of the day and
year first above written.

ATTEST:                                   MOTIENT HOLDINGS INC.

    /s/  Thomas J. Portman                By    /s/  Walter V. Purnell, Jr.
--------------------------------------      -----------------------------------
        Thomas J. Portman                            Walter V. Purnell, Jr.
Associate Counsel and Secretary           President and Chief Executive Officer



ATTEST:                                   M&E ADVISORS L.L.C.
                                              as Collateral Agent

    /s/  Deborah Scarnati                     By    /s/  Gary Singer
------------------------------------------      -------------------------------
        Deborah Scarnati                               Gary Singer
                                              Investment Advisor