Document:

<Page>

[MOTIENT LOGO]
                                                                EXHIBIT 10.6b
                      MOTIENT CORPORATION STOCK AWARD PLAN
                           RESTRICTED STOCK AGREEMENT
                                NOTICE OF GRANT

EMPLOYEE NAME                        RESTRICTED STOCK NUMBER: RS2001___________
ADDRESS 1                            PRIOR OPTION NUMBER:     _________
ADDRESS 2                            PLAN:                    STOCK AWARD PLAN
CITY, STATE ZIP                      ID:                      SOCIAL SECURITY #

Effective September 25, 2001, you ("Grantee") have been granted an award of
Restricted Stock in the amount of ____ shares (the "Covered Shares") of Motient
Corporation (the "Corporation") common stock in exchange for the cancellation of
Options previously granted to you. Your Restricted Stock is subject to the terms
and conditions set forth in this Agreement and under the Plan.

You were previously issued a grant of stock options under the Plan and/or the
Directors' Plan pursuant to a stock option agreement dated ______________,
______ (the "Prior Option"). This grant of Restricted Stock is being made in
exchange for your agreement to cancel the Prior Option. Your Prior Option,
therefore, has been cancelled and is null and void, and this Agreement
supercedes the terms of the agreement under which the Prior Option was granted.

Your right to the stock covered by the Restricted Stock grant vests as follows,
commencing on March 25, 2002 (the "First Vesting Date"), if you continue to be
an employee, director or other service provider of the Corporation or a
Subsidiary on that date. If on the First Vesting Date you remain in such
continuous service, the vested percentage that you would have had as of such
date under the agreement relating to your Prior Option shall be reinstated and
shall be applied to your Restricted Stock. The Shares thus becoming vested shall
cease to be Restricted Stock. In addition, the vesting schedule under your Prior
Option shall continue to apply to your remaining Restricted Stock. If you
terminate service with the Corporation and all Subsidiaries on account of a
downsizing on or prior to the First Vesting Date, your Restricted Stock shall
become vested as of such date, but only to the extent of the vested percentage
that you would have had as of such date under your Prior Option.

Upon meeting the conditions outlined above at the First Vesting Date, the shares
in each period will become fully vested on the date shown, if you continue to be
an employee, director or other service provider of the Corporation or a
Subsidiary on that date.

     SHARES                       VEST TYPE                   FULL VEST
     ------                       ---------                   ---------
     ____                         Annually                    ______
     ____                         Annually                    ______
     ____                         Annually                    ______

By your signature and the Corporation's signature below, you and the Corporation
agree that this Restricted Stock is granted under and governed by the terms and
conditions of the Plan, a copy of which is attached to and incorporated into
this Agreement, and by this Agreement in its entirety, including the agreement
terms on the pages to follow.

--------------------------------------               ---------------------------
Motient Corporation                                  Date

--------------------------------------               ---------------------------
Employee Name                                        Date

                                       1

<Page>
[MOTIENT LOGO]
                                                                   Attachment to
                                                                       Grants of
                                                                Restricted Stock
                                                              September 25, 2001

                      MOTIENT CORPORATION STOCK AWARD PLAN
                           RESTRICTED STOCK AGREEMENT

                                 AGREEMENT TERMS

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

     (a) "Agreement" means this Restricted Stock 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 of Restricted Stock defined as the
"Covered Shares" on page 1 [the Notice of Grant page].

     (d) "Disability" means permanent and total disability of the Grantee, as
determined by the Committee.

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

     (f) "Involuntary Termination" means termination by the Corporation or a
Subsidiary of the Grantee'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
Grantee, but, in all cases, does not include any such termination or substantial
reduction as a result of the commission of a felony by the Grantee, and does not
include Termination for Good Cause.

     (g) "Plan" means the Motient Corporation Stock Award Plan, amended and
restated May 23, 2000.

     (h) "Restricted Stock" means the restricted stock granted to the Grantee in
Paragraph 2 of this Agreement, to the extent such stock is not yet vested.

     (i) "Termination for Good Cause" means termination due to (i) the
commission of a felony or a crime involving moral turpitude or the commission of
any other act or omission involving dishonesty or fraud with respect to the
Corporation or any of its affiliates or any of their customers or suppliers,
(ii) conduct tending to bring the Corporation or any of its affiliates into
substantial public disgrace or disrepute, (iii) substantial and repeated failure
to perform duties of the office or position held by the Grantee as reasonably
directed by the Corporation, and such failure is not cured within 30 days after
the Grantee receives notice thereof from the Corporation, (iv) gross negligence
or willful misconduct with respect to the Corporation or any of its affiliates
or (v) any material breach of any agreement between the Grantee and the
Corporation.

2.   GRANT OF RESTRICTED STOCK. The Corporation hereby grants to the Grantee,
pursuant to the Plan and subject to the terms of this Agreement, Restricted
Stock equal to the number of Covered Shares set forth in the Notice of Grant.

3.   TERMS OF THE RESTRICTED STOCK.

     (a) VESTING SCHEDULE. Your right to the stock covered by the Restricted
Stock grant vests as provided in the Notice of Grant.

                                       2
<Page>

     (b) FORFEITURE. Except as next described, all of your Restricted Stock
(i.e., stock which is not already vested under the provisions of Section 3(a))
is forfeited upon your termination of service with the Corporation and all
Subsidiaries. If you terminate service by reason of your death or your
Disability, your Restricted Stock shall not be forfeited but shall instead
become fully vested.

     (c) CHANGE OF CONTROL. Notwithstanding the provisions of Section 3(a), if a
Change of Control occurs, the Grantee shall be entitled to receive Equivalent
Restricted Stock. If the transaction is structured such that the Grantee cannot
receive Equivalent Restricted Stock in connection with such Change of Control,
(i) the Grantee shall be entitled to receive immediately prior to such Change of
Control, and in exchange for his or her Restricted Stock, cash in an amount
equal to the excess of the highest price paid for a Share in connection with the
Change of Control, multiplied by the total number of Covered Shares which have
not yet vested under the provisions of Section 3(a), or (ii) if the Grantee is
an Insider who would be subject to suit under Section 16(b) of the Exchange Act
if the Grantee were to receive the cash payment described in Section 3(c)(i),
the Restricted Stock becomes fully vested beginning on the date two weeks before
such Change of Control. If the Grantee receives Equivalent Restricted Stock in
connection with a Change of Control, and the Grantee'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 Restricted Stock
will become fully vested beginning on the date of such termination.

     (d) ESCROW.

         (i) The certificates for the Restricted Stock shall be deposited in
escrow with the Secretary of the Corporation to be held in accordance with the
provisions of this paragraph. The deposited certificates shall remain in escrow
until such time or times as the certificates are to be released or otherwise
surrendered for cancellation as discussed below. Upon delivery of the
certificates to the Corporation, you shall be issued an instrument of deposit
acknowledging the number of shares of Restricted Stock delivered in escrow to
the Secretary of the Corporation.

           (ii) In the event of any stock dividend, stock split, combination,
recapitalization or other change affecting the Corporation's outstanding common
stock as a class effected without receipt of consideration or in the event of a
stock split, a stock dividend, combination, or a similar change in the
Corporation's outstanding common stock, any new, substituted or additional
securities or other property which is by reason of such transaction distributed
with respect to the Corporation's outstanding common stock shall be immediately
delivered to the Secretary of the Corporation to be held in escrow hereunder,
but only to the extent the Restricted Stock is at the time subject to the escrow
requirements hereof.

          (iii) As your interest in the Restricted Stock vests as described in
3(a), the certificates for such vested shares shall be released from escrow and
delivered to you, at your request, within thirty (30) days of such vesting or
immediately upon your termination of employment with the Corporation.

4.   SECTION 83(B) ELECTION. Under Section 83 of the Internal Revenue Code, you
will recognize ordinary income equal to the fair market value of the Shares
received from the Restricted Stock on the date you vest. However, you may elect
to be taxed at the time the Restricted Stock is granted, rather than when the
Restricted Stock becomes vested and ceases to be Restricted Stock. To elect this
early taxation, you would need to file an election under Section 83(b) of the
Code with the Internal Revenue Service within thirty (30) days after the Date of
Grant. In addition, you would have to make a payment to the Corporation to cover
the withholding on the fair market value of the Restricted Stock on the Date of
Grant. The form for making this election is attached as EXHIBIT A hereto.

     YOU ARE RELYING SOLELY ON YOUR OWN ADVISORS WITH RESPECT TO THE DECISION AS
TO WHETHER OR NOT TO FILE ANY SECTION 83(b) ELECTION. IF YOU DETERMINE THAT THE
ELECTION IS ADVISABLE, YOU ACKNOWLEDGE THAT IT IS YOUR SOLE RESPONSIBILITY, AND
NOT THE CORPORATION'S, TO FILE A TIMELY ELECTION UNDER SECTION 83(b). THIS IS SO
EVEN IF YOU REQUEST THE CORPORATION OR ITS REPRESENTATIVES TO MAKE THIS FILING
ON YOUR BEHALF.

5.   LEGENDS. All certificates representing the Restricted Stock issued in
connection with this grant shall, where applicable, have endorsed thereon the
following legends:

     "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
RESTRICTIONS ON TRANSFER SET FORTH IN AN AGREEMENT BETWEEN THE CORPORATION AND
THE REGISTERED HOLDER. A COPY OF SUCH AGREEMENT IS ON FILE AT THE PRINCIPAL
OFFICE OF THE CORPORATION AND WILL BE FURNISHED UPON WRITTEN REQUEST BY THE
SECRETARY OF THE CORPORATION TO THE HOLDER OF RECORD OF THE SHARES REPRESENTED
BY THIS CERTIFICATE."

6.   RIGHTS AS STOCKHOLDER. The Grantee has the right to vote the Restricted
Stock and to receive any dividends declared or paid on such stock. Any
distributions Grantee receives as a result of any stock split, stock dividend,
combination of shares or other similar transaction shall be deemed to be a part
of the Restricted Stock and subject to the same conditions, restrictions, and
escrow arrangements applicable thereto. The Corporation may, in its sole
discretion, require any dividends paid on the Restricted Stock to be reinvested
in shares of the Corporation's common stock, which the Corporation may in its
sole discretion deem to be a part of the shares of Restricted Stock and subject
to the same conditions, restrictions and escrow arrangements applicable thereto.
Otherwise, all regular cash dividends paid on the Restricted Stock (or other
securities at the time held in escrow) shall be paid directly to you and shall
not be held in escrow. No adjustments are made for dividends or other rights if
the applicable record date occurs before your stock certificate is issued.

7.   ADJUSTMENTS. In the event of a stock split, a reverse stock split, a stock
dividend or a similar change in the Corporation's common stock, the number of
shares of Restricted Stock shall be adjusted (and may be rounded down to the
nearest whole number) pursuant to the Plan. Your Restricted Stock shall be
subject to the terms of an agreement of merger, liquidation or reorganization in
the event the Corporation is subject to such corporate activity.

8.   EMPLOYMENT. Neither the granting of the Restricted Stock 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 Grantee for any period.
Whenever reference is made in this Agreement to the employment of the Grantee,
it means employment by the Corporation or a subsidiary.

                                       3
<Page>

9.   SUBJECT TO THE PLAN. The shares of Restricted Stock evidenced by this
Agreement are subject to the terms and conditions of the Plan, which are
incorporated herein by reference and made a part hereof. In addition, the
Restricted Stock is subject to any rules and regulations promulgated by the
Committee consistent with the terms of the Plan.

                                      4

<Page>

                                    EXHIBIT A

                         ELECTION UNDER SECTION 83(B) OF
                            THE INTERNAL REVENUE CODE

     The undersigned hereby makes an election pursuant to Section 83(b) of the
Internal Revenue Code with respect to the property described below and supplies
the following information in accordance with the regulations promulgated
thereunder:

          1. The name, address and social security number of the undersigned:

             Name:
                  --------------------------------------------------------------
             Address:
                     -----------------------------------------------------------

             Social Security No.:
                                 -----------------------------------------------

          2. Description of property with respect to which the election is being
             made:

             ______shares of common stock, par value $.01 per share, Motient
             Corporation, a Delaware corporation, (the "Corporation").

          3. The date on which the property was transferred is September 25,
             2001.

          4. The taxable year to which this election relates is calendar year
             2001.

          5. Nature of restrictions to which the property is subject:

             The shares of stock are subject to the provisions of a Restricted
             Stock Agreement between the undersigned and the Corporation. The
             shares of stock are subject to forfeiture under the terms of the
             Agreement.

          6. The fair market value of the property at the time of transfer
             (determined without regard to any lapse restriction) was $0.13 per
             share, for a total of $__________.

          7. The amount paid by taxpayer for the property was $0.00.

          8. A copy of this statement has been furnished to the Corporation.

Dated:  _____________, 2001

                                             ___________________________________
                                             Taxpayer's Signature

                                             ___________________________________
                                             Taxpayer's Printed Name

                                       A-1
<Page>

                         PROCEDURES FOR MAKING ELECTION
                    UNDER INTERNAL REVENUE CODE SECTION 83(b)

     The following procedures must be followed with respect to the attached form
for making an election under Internal Revenue Code section 83(b) in order for
the election to be effective:

     1. You must file one copy of the completed election form with the IRS
Service Center where you file your federal income tax returns within 30 days
after the Date of Grant for your Restricted Stock.

     2. At the same time you file the election form with the IRS, you must also
give a copy of the election form to the Secretary of the Corporation.

     3. YOU MUST FILE ANOTHER COPY OF THE ELECTION FORM WITH YOUR FEDERAL INCOME
TAX RETURN (GENERALLY, FORM 1040) FOR THE TAXABLE YEAR IN WHICH THE STOCK IS
TRANSFERRED TO YOU.

INTERNAL REVENUE SERVICE LOCATIONS:

DISTRICT OF COLUMBIA FILERS:                  MARYLAND FILERS:
Internal Revenue Service                      Internal Revenue Service
Philadelphia, PA 19255                        Philadelphia, PA  19255

ILLINOIS FILERS:                              VIRGINIA FILERS:
Internal Revenue Service                      Internal Revenue Service
Kansas City, MO 64999                         Philadelphia, PA 19255

For additional locations, please visit:
http://www.irs.ustreas.gov/plain/where_file/

                                       A-2<Page>

                                                                  EXHIBIT 10.14b

                               SUBLEASE AGREEMENT

     THIS SUBLEASE AGREEMENT ("Sublease") is entered into as of this 26th day of
November, 2001, by and between Mobile Satellite Ventures LP, a Delaware limited
partnership ("Sublandlord"), and Motient Services Inc., a Delaware corporation
("Subtenant").

                                    RECITALS

A. Sublandlord is the tenant under that certain Deed of Lease by and between
Trust Company of the West, as Trustee of TCW Realty Fund II,
predecessor-in-interest to APA Properties No. 10, L.P., as landlord ("Master
Landlord"), and Motient Services Inc. (formerly AMSC Subsidiary Corporation)
dated February 4, 1993, as amended by Amendment No. 1 dated June 21, 1993;
Amendment No. 2 dated January 27, 1994; Amendment No. 3 dated May 24, 1994, and
Amendment No. 5 dated October 7, 1994 (the "Master Lease"), for certain space
located at 10800-10802 Parkridge Boulevard, Reston, Virginia, 22091 (the
"Premises").

B. Subtenant wishes to sublease a portion of the Premises from Sublandlord.

                                   AGREEMENT

     Now, therefore, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereby agree as
follows:

         1.       Basic Sublease Information.

                  The information set forth in this section (the "Basic

                                     Page 1
<Page>

Sublease Information") is intended to supplement and/or summarize the provisions
set forth in the balance of this Sublease. Each reference in this Sublease to
any of the terms set forth below shall mean the respective information set forth
next to such term as amplified, construed or supplemented by the particular
Section(s) of the Sublease pertaining to such information. In the event of a
conflict between the provisions of this Section and balance of the Sublease, the
balance of the Sublease shall control.

<Table>
<S>                                        <C>

SUBLANDLORD:                               Mobile Satellite Ventures LP,
                                           a Delaware limited partnership

Sublandlord's Address                      Mobile Satellite Ventures LP
for Notices:                               10800-10802 Parkridge Boulevard
                                           Reston, Virginia  22091
                                                    Attn:  Managing Director

Subtenant:                                 Motient Services Inc.,
                                           a Delaware corporation

SUBTENANT'S ADDRESS                        Motient Services Inc.
FOR NOTICES:                               10800-10802 Parkridge Boulevard
                                           Reston, Virginia  22091
                                                    Attn:  Manager, Facilities

SUBDEMISED PREMISES:                       The portion of the Premises described
                                           on Exhibit A, as may be modified from
                                           time to time upon the mutual
                                           agreement of Sublandlord, Subtenant
                                           and Landlord.

Building:                                  10800-10802 Parkridge Boulevard,
</Table>

                                     Page 2
<Page>

<Table>
<S>                                        <C>
                                           Reston, Virginia

PERMITTED USE:                             Specified in Article 10 of the Master
                                           Lease as general office, sales and
                                           marketing offices and other lawful
                                           uses.

RENT:                                      Fifty  percent (50%) of total Base
                                           Rent and  Additional  Rent as set
                                           forth in, defined, and due under the
                                           Master Lease.

TERM COMMENCEMENT DATE:                    The term of the  Sublease  shall
                                           commence  upon the  later of
                                           (i) Sublandlord's receipt of written
                                           approval of this Sublease from Master
                                           Landlord and (ii) the effective  date
                                           of the Assignment and Assumption of
                                           Lease entered into between
                                           Sublandlord  and Subtenant (the
                                           "Assignment and  Assumption")
                                           pursuant to which Subtenant shall
                                           assign its interest in the Master
                                           Lease to Sublandlord. Promptly
                                           following the Term Commencement Date,
                                           Sublandlord will deliver to Subtenant
                                           a notice, identifying the Term
                                           Commencement Date and Expiration
                                           Date, a copy of which notice shall be
                                           executed by  Subtenant  and promptly
                                           returned to Sublandlord.

EXPIRATION DATE:                           The Expiration Date shall be
                                           August 2, 2003.

RENT COMMENCEMENT DATE:                    The Rent Commencement Date shall be
                                           the same as Term Commencement Date.

SUBTENANT'S INSURANCE:                     Specified and as required in
                                           Article 17 of the Master Lease.
</Table>

         2.       Sublease.

                                     Page 3
<Page>

                  Sublandlord hereby subleases to Subtenant, and Subtenant
hereby subleases from Sublandlord, the Subdemised Premises upon all of the
terms, covenants and conditions in this Sublease.

         3.       Delivery Condition.

                  Subtenant acknowledges that it takes possession of the
Subdemised Premises in its "as is" condition, and further acknowledges that
Sublandlord has made no representations or warranties of any kind or nature,
whether express or implied, with respect to the Subdemised Premises, Common
Areas, or Building, nor has Sublandlord agreed to undertake or perform any
modifications, alterations, or improvements of the Subdemised Premises, Common
Areas, nor has Sublandlord agreed to undertake or perform any modifications,
alterations, or improvements of the Premises, Common Areas, or the Building
which would inure to Subtenant's benefit.

         4.       Term.

                  4.1 INITIAL TERM. The initial term of this Sublease shall
commence on the Term Commencement Date, and shall expire on the Expiration Date.

                  4.2 Surrender. Subtenant shall, upon the Expiration Date or
earlier termination of this Sublease, remove all personal property, furniture,
and trade fixtures, provided that removal of the same does not adversely affect
the adversely affect the Building structure or any Building operating system,
and that Subtenant repairs any damage to the Building structure or its operating
systems caused by such removal pursuant to the requirements of the Master Lease.
In the event

                                      Page 4
<Page>

Subtenant fails to remove its personal property and equipment as specified in
this Section 4.2 by the Expiration Date, all such items remaining on the
Subdemised Premises shall be deemed abandoned and Sublandlord may dispose of it
as it sees fit, without liability to Subtenant. Sublandlord shall be responsible
for the removal of all Alterations as required under the Master Lease, including
Alterations installed by Subtenant under the Master Lease prior to the effective
date of the Assignment and Assumption. Subtenant shall be responsible for
removal of all Alterations installed by Subtenant pursuant to this Sublease. In
all other respects, Subtenant shall deliver the Premises broom clean, in its
condition as of the Term Commencement Date, reasonable wear and tear and
casualty excepted. In no event shall Subtenant remove any of the plumbing,
electrical, data lines, and HVAC system(s).

                  Subtenant shall vacate and deliver possession of the
Subdemised Premises free of all liens, charges or encumbrances resulting from
any act or omission on Subtenant's part, and free and clear of all violations
thereon placed by any federal, state, municipal or other agency or authority by
reason of Subtenant's failure to fulfill any of its obligations under this
Sublease ("Violations"). Subtenant shall indemnify Sublandlord against any and
all loss, expense, damage, costs or attorneys' fees arising out of Violations
occurring after the Term Commencement Date. Sublandlord shall indemnify
Subtenant against any and all loss, expense, damage, costs or attorneys' fees
arising out of any Violation occurring prior to the Term Commencement Date. The
voluntary or other surrender of this Sublease by Subtenant, or a mutual
cancellation thereof, shall not work a merger, but shall, at the option of
Sublandlord, either (1) terminate all or any existing subleases or subtenancies,

                                     Page 5
<Page>

or (2) operate as an assignment of Sublandlord of any or all such subleases or
subtenancies.

                  4.4 Holding Over. If Subtenant remains in possession of the
Subdemised Premises after the then current Expiration Date, such occupancy shall
constitute a tenancy at sufferance, and Subtenant shall be obligated to pay 200%
rental installments as specified in Section 5 of this Sublease and Subtenant
shall be liable to Sublandlord for any and all claims, damages, liabilities,
costs and expenses (including attorneys, fees and expenses) incurred by
Sublandlord and arising out of Subtenant's failure to timely surrender the
Subdemised Premises in accordance with the requirements of this Sublease.

         5.       Rent.

                  As used in this Sublease, the term "Rent" shall include
(1) Base Rent, (2) Additional Rent and (3) all other amounts which Subtenant is
obligated to pay under the terms of this Sublease.

                  5.1 Rent. Rent is as specified in Section 1 (Basic Sublease
Information). Rent shall be paid each month, without offset or deductions, on or
before the first day of the month to Sublandlord at the Sublandlord's address in
Section 1.

                  Notwithstanding the above, Subtenant shall be solely
responsible for any and all increases in Rent or any added cost or charge which
has arisen solely because of Subtenant's tenancy in the Subdemised Premises,
including any and all heat, water and sewer charges, electric and other utility
charges, as well as any other service charges required by the Master Lease and
relating to the Subdemised Premises.

                                      Page 6
<Page>

                  5.2 Late Charges. In addition to such remedies as may be
provided in the Master Lease or this Sublease, if Subtenant fails to pay any
Rent when due, Sublandlord shall be entitled to a late charge and interest as
set forth in the Article 22.6 of the Master Lease.

         6.       Use and Compliance With Laws.

                  Subtenant shall use the Subdemised Premises for the Permitted
Use (as specified in the Basic Sublease Information) during the term of this
Sublease, and for no other use or uses. Subtenant shall not engage in any
activities prohibited by the Master Lease. Subtenant will not use or store
flammable or hazardous materials on the Subdemised Premises. Subtenant shall not
perform any act or carry on any practice which may injure the Subdemised
Premises or cause any offensive odors or noises that constitute a nuisance or
menace to any other tenant or tenants or other persons, and in no event shall
any noises or odors be emitted from the Subdemised Premises. Nothing shall be
done upon or about the Subdemised Premises which shall be unlawful, improper, or
contrary to any law, ordinance, regulation or requirement of any public
authority or insurance inspection or rating bureau or similar organization
having jurisdiction and Subtenant will promptly comply with any such law,
ordinance, regulation or requirement. Subtenant will observe and comply with,
and will cause its employees, agents and invitees to observe and comply with the
restrictions set forth herein. Subtenant agrees to comply with all rules and
regulations that Master Landlord has made or may hereafter from time to time
make for the Building. Sublandlord shall not be liable in any way for damage

                                      Page 7
<Page>

caused by the non-observance by any of the other tenants of such similar
covenants in their leases or of such rules and regulations.

         7.       Insurance.

                  Subtenant shall obtain at its sole expense the insurance
required under Article 17 of the Master Lease effective as of the Term
Commencement Date. Additionally, Subtenant shall name Sublandlord and Master
Landlord as additional insureds, as their interests may arise or may appear, and
shall furnish Sublandlord with certificates of insurance from its insurer, with
respect to such insurance, and shall deliver such certificate to Sublandlord on
or before the Term Commencement Date.

         8.       Assignment and Subletting.

                  Subtenant shall not directly or indirectly, voluntarily or by
operation of law, sell, assign, encumber, pledge or otherwise transfer or
hypothecate all of its interest in or rights with respect to the Premises or
Subtenant's leasehold estate hereunder (collectively, "Assignment"), or permit
all or any portion of the Premises to be occupied by anyone other than Subtenant
(pursuant to a license, concession or otherwise) or sublet all or any portion of
the Premises or transfer a portion of its interest in or rights with respect to
Subtenant's leasehold estate hereunder. Subject to Master Landlord's consent
under Article 11 of the Master Lease, Subtenant may assign, sublet or otherwise
transfer its interest in this Sublease with Sublandlord's consent, to any
parent, subsidiary or affiliate of Subtenant, or to a corporation or other
business entity with which Subtenant may merge, amalgamate or consolidate.

         9.       Alterations.

                                     Page 8
<Page>

                  Subtenant shall not make or suffer to be made any alterations,
additions or improvements to the Subdemised Premises, including those related to
electrical, data cabling, or modifications to existing finishes, without the
prior written consent of Master Landlord, as required under the Master Lease,
and of Sublandlord, which approval with respect to Sublandlord shall not be
unreasonably withheld. It shall be deemed reasonable for Sublandlord to withhold
its consent to proposed alterations hereunder if Subtenant's proposed
alterations, additions, or improvements adversely affect the Sublandlord's use
of the Premises following the Sublease Expiration Date or if they do not satisfy
the criteria set forth in the Master Lease. Additionally, Subtenant shall be
subject to the standards for repairs and alterations set forth in the Master
Lease.

         10.      Repairs and Maintenance.

                  10.1 SUBTENANT'S RESPONSIBILITY.  Subtenant shall be
responsible for the maintenance and repair of the Subdemised Premises pursuant
to the provisions of Article 12.2 of the Master Lease.

                  10.2 Sublandlord's Responsibility. As between the parties to
this Sublease, Sublandlord shall have no responsibility for the Subdemised
Premises including, without: limitation, the roof, roof covering, foundation,
subfloors, building structural components, major building systems (plumbing,
electrical and heating, air conditioning and ventilation systems), and exterior
walls of the Subdemised Premises, during the Sublease.

         11.      Default.

                  11.1 Events of Default. Subtenant shall be subject to the same

                                     Page 9
<Page>

default provisions as specified in Article 22 of the Master Lease, and
Sublandlord shall have all the remedies specified in Article 22, as if it were
Master Landlord, including, without limitation, the right to terminate the
Sublease and right to perform Subtenant's obligations under this Sublease.

         13.      Indemnity.

                  In addition to such indemnities as may be provided for in the
Master Lease, Subtenant agrees to indemnify and hold Sublandlord harmless
against all loss, damage, liability, or expense arising out of injury to third
parties or their property (i) caused by any breach or default by Subtenant of
any covenant or obligation it has hereunder (including but not limited to all
covenants or obligations of the tenant under the Master Lease assumed by
Subtenant pursuant to the terms of this Sublease), or (ii) caused by or in
connection with anything owned or controlled by Subtenant, or (iii) resulting
from any act, failure to act, or negligence of Subtenant or its employees,
agents or invitees, or (iv) resulting from any nuisance suffered on the
Subdemised Premises, except for damage or injury to third parties or property
resulting from the proven gross negligence of Sublandlord. Subtenant further
agrees to indemnify Sublandlord and hold Sublandlord harmless from all losses,
damages, liabilities and expenses which Sublandlord may incur, or for which
Sublandlord may be liable to Master Landlord, arising from the acts or omissions
of Subtenant which are or are alleged to be defaults under the Master Lease or
are the subject matter of any indemnity or hold harmless of Sublandlord, as
tenant, to Master Landlord under the Master Lease.

         14.      Master Lease.

                                    Page 10
<Page>

                  14.1 Master Lease Provisions. Notwithstanding anything in this
Sublease to the contrary, the rights of Subtenant shall be subject to and
limited by the terms and conditions contained in the Master Lease between
Sublandlord and the Master Landlord, as it may be amended from time to time.
Subtenant hereby acknowledges receipt of a copy of the Master Lease. Sublandlord
shall have the right to amend the Master Lease from time to time without the
consent of Subtenant provided that any such amendment shall not adversely affect
Subtenant's ability to continue its then current operations in the Subdemised
Premises, increase any of the rental or other payments required to be made by
Subtenant or otherwise materially change the agreement between Subtenant and
Sublandlord. Sublandlord shall endeavor to give Subtenant notice of any
amendment to the Master Lease, but the failure to give such notice shall not
affect the validity of such amendment or its applicability to Subtenant, except
that Subtenant shall have no obligation to comply with the terms of any such
amendment until it has received a copy. Any rights granted herein which are
limited by the Master Lease shall be deemed to be so limited by this Sublease.

                  14.2 No Violation. Notwithstanding anything in this Sublease
to the contrary, neither party shall commit or permit to be committed any act or
omission which shall violate any term or condition of the Master Lease. Each
party shall indemnify and hold harmless the other party from and against any
loss, liability, claim, cost or expense (including reasonable attorneys' fees)
incurred by the other party as a result of any termination or attempted
termination of the Prime Lease resulting from any such act or omission by the
other party.

                                    Page 11
<Page>

                  14.3 Consent of Master Landlord. Notwithstanding anything in
this Sublease to the contrary, the effectiveness of this Sublease shall be
conditioned upon Sublandlord obtaining the written consent of the Master
Landlord under the Master Lease to this Sublease in form and substance
satisfactory to Sublandlord and Subtenant. If the consent of the Master Landlord
is not obtained, this Sublease shall be void.

                  14.4 TERMINATION OF MASTER LEASE. If the Master Lease
terminates for any reason, this Sublease shall terminate concurrently therewith
without any liability of  Sublandlord to Subtenant.

                  14.5 Incorporation of Master Lease Terms. This Sublease and
Subtenant's rights under this Sublease shall at all times be subject to all of
the terms, covenants, and conditions of the Master Lease, with the same force
and effect as if fully set forth herein at length, and except as otherwise
expressly provided for herein, Subtenant shall keep, observe and perform or
cause to be kept, observed and performed, faithfully all those terms, covenants
and conditions of Sublandlord as tenant under the Master Lease with respect to
the Subdemised Premises. Except as otherwise provided hereby, the terms,
conditions, rights and responsibilities of the Master Lease are incorporated
herein by reference, and Sublandlord shall have the rights and responsibilities
with respect to the Subtenant that the Master Landlord has with respect to
Sublandlord pursuant to the Master Lease, and Subtenant shall have the rights
and responsibilities with respect to Sublandlord that Sublandlord has with
respect to the Master Landlord pursuant to the Master Lease. With respect to the
relationship between the Sublandlord and the Subtenant, the terms, covenants

                                    Page 12
<Page>

and conditions of this Sublease shall control with respect to any conflict or
inconsistency between the terms, covenants and conditions contained herein and
the terms, covenants and conditions of the Master Lease.

         15.      Counterparts.

                  This Sublease may be executed in one or more counterparts,
each of which shall constitute one and the same instrument.

         16.      Governing Law.

                  This Agreement shall be governed by and construed and enforced
in accordance with the laws of the Commonwealth of Virginia, except with respect
to the choice-of-law provisions thereof.

         17.      Continuing Obligations.

                  Notwithstanding this Sublease, Subtenant shall remain liable
for the obligations of "Tenant" under the Master Lease, and Motient Corporation
(formerly American Mobile Satellite Corporation) ("Guarantor") shall remain
liable for its obligations under that certain Guaranty of Lease made as of
February 4, 1993 to Master Landlord.

                            [Signature page follows]

         IN WITNESS WHEREOF, this Sublease shall be deemed to have been executed
as of the date first set forth above.

                                              SUBLANDLORD:

                                              MOBILE SATELLITE VENTURES LP,

                                    Page 13
<Page>

                                              a Delaware limited partnership

                                              By: /s/Carson E. Agnew
                                                  ------------------
                                                  Name: Carson E. Agnew
                                                  Title: Managing Director
                                                  Dated: November 26, 2001

                                              SUBTENANT:

                                              MOTIENT SERVICES INC.,
                                              A Delaware corporation

                                              By: /s/David H. Engvall
                                                  -------------------
                                                  Name: David H. Engvall
                                                  Title: Vice President
                                                  Dated: November 26, 2001

Not as a party, but solely to acknowledge its continuing obligations as
guarantor described in Section 17.

                                              GUARANTOR:

                                              MOTIENT CORPORATION
                                              A Delaware corporation

                                              By: /s/David H. Engvall
                                                  -------------------
                                                  Name: David H. Engvall
                                                  Title: Vice President
                                                  Dated: November 26, 2001

                                    Page 14
<Page>

                                EXHIBIT OMITTED

                                    Page 15

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00036-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00036-of-00352.parquet"}]]