Document:

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                                                                        EX 10.17

                       FIRST AMENDMENT TO LEASE AGREEMENT

      THIS FIRST AMENDMENT TO LEASE AGREEMENT (this "AMENDMENT") is made and
entered into as of the ____ day of ________, 2001, by and between BUILDING VI
ASSOCIATES L.C., a Virginia limited liability company ("LANDLORD"), and PEC
SOLUTIONS, INC., a Delaware corporation ("TENANT").

                                   RECITALS:

      A. Landlord and Tenant entered into that certain Office Lease Agreement
dated February 5, 2001 (the "LEASE"), whereby Landlord leased to Tenant and
Tenant leased from Landlord the Premises (as defined in the Lease).

      B. Except as otherwise provided herein to the contrary, all capitalized
terms used in this Amendment shall have the same meanings as are attributed
thereto in the Lease.

      C. Landlord and Tenant desire to amend the Lease as more fully described
in this Amendment.

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth herein and of other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Landlord and Tenant, intending
legally to be bound, hereby agree as follows:

      1. Article One Section 1.01 F and G are hereby deleted in their entirety
and the following is inserted in lieu thereof:

            "F. Rentable Area of the Building: The Building shall contain
            approximately 150,000 square feet of total Rentable Area, subject to
            final measurement pursuant to Section 1.03 of Exhibit "C".

            G. Rentable Area of the Premises: The Premises shall contain
            approximately 150,000 square feet of Rentable Area, subject to final
            measurement pursuant to Section 1.03 of Exhibit "C".

      2. Landlord and Tenant agree that immediately after final measurement of
the Building and the Premises in accordance with Section 1.03 of Exhibit "C" of
the Lease, Landlord and Tenant shall execute a Commencement Date Certificate in
the form attached hereto as EXHIBIT "A" that sets forth, among other things, the
final Rentable Area of the Building and the Premises.

      3. Except as modified in this Amendment, the Lease remains unmodified and
in full force and effect.

      IN WITNESS WHEREOF, Landlord and Tenant have caused this Amendment to be
signed and sealed by their duly authorized signatories under

                                       1
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seal as of the day and year first above written.

                                  LANDLORD:

                                  BUILDING VI ASSOCIATES L.C.

                                  By:                            (SEAL)
                                         -----------------------
                                  Name:
                                         -------------------------------
                                  Title:
                                         -------------------------------

                                  TENANT:

                                  PEC SOLUTIONS, INC.

                                  By:                            (SEAL)
                                         -----------------------
                                  Name:
                                         -------------------------------
                                  Title:
                                         -------------------------------

                                       2
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                                  EXHIBIT "A"

                            COMMENCEMENT DATE NOTICE

      THIS COMMENCEMENT DATE NOTICE (the "COMMENCEMENT DATE NOTICE") is made and
entered into this ____ day of ________________, 200_ by and between BUILDING VI
ASSOCIATES L.C. ("LANDLORD") and PEC SOLUTIONS, INC. ("TENANT"), wherein
Landlord and Tenant have entered into that certain Office Lease Agreement dated
February 5, 2001 (the "LEASE"). Unless otherwise defined herein, all capitalized
terms used herein shall have the same meaning as described in the Lease.

                                  WITNESSETH:

      WHEREAS, Landlord and Tenant wish to confirm and memorialize the
Commencement Date, the Expiration Date and the Rentable Area of the Premises and
the Building as defined in the Lease, Landlord and Tenant agree as follows:

      1. The Commencement Date as defined in the Lease is established to be
___________________, _____.

      2. The Expiration Date as defined in the Lease is established to be
___________________, _____.

      3. The Rentable Area of the Building as defined in the Lease is
________________________.

      4. The Rentable Area of the Premises as defined in the Lease is
________________________.

      5. The Landlord's work and/or delivery of the Premises as required by the
Lease has been substantially completed.

      6. Tenant has accepted possession of the Premises pursuant to the terms of
the Lease.

                                       3
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         Except as described herein, all terms and conditions of the Lease are
and shall remain in full force and effect.

                                          LANDLORD:

                                          BUILDING VI ASSOCIATES L.C.,
                                          a Virginia limited liability company

                                          By:
                                                 -------------------------------
                                          Name:
                                                 -------------------------------
                                          Title:
                                                 -------------------------------

                                          TENANT:

                                          PEC SOLUTIONS, INC.
                                          a Delaware corporation

                                          By:
                                                 -------------------------------
                                          Name:
                                                 -------------------------------
                                          Title:
                                                 -------------------------------

                                       4<Page>

                                                                       EX. 10.18

                      SECOND AMENDMENT TO LEASE AGREEMENT

      THIS SECOND AMENDMENT TO LEASE AGREEMENT (this "SECOND AMENDMENT") is made
and entered into as of the 11th day of May, 2001, by and between BUILDING VII
ASSOCIATES L.C., a Virginia limited liability company formerly known as Building
VI Associates L.C. ("LANDLORD"), and PEC SOLUTIONS, INC., a Delaware corporation
("TENANT").

                                   RECITALS:

      A. Landlord and Tenant entered into that certain Office Lease Agreement
dated February 5, 2001, amended by First Amendment to Lease Agreement dated May
7, 2001 (the "LEASE"), whereby Landlord leased to Tenant and Tenant leased from
Landlord the Premises (as defined in the Lease).

      B. Except as otherwise provided herein to the contrary, all capitalized
terms used in this Amendment shall have the same meanings as are attributed
thereto in the Lease.

      C. Landlord and Tenant desire to amend the Lease as more fully described
in this Amendment.

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth herein and of other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Landlord and Tenant, intending
legally to be bound, hereby agree as follows:

      1. The name of Landlord was changed from Building VI Associates L.C. to
BUILDING VII ASSOCIATES L.C., effective May 11, 2001. All references to Landlord
in the Lease shall hereinafter reflect such name change and shall be demed to
refer to Building VII Associates L.C.

      2. Except as modified in this Amendment, the Lease remains unmodified and
in full force and effect.

                                       1
<Page>

      IN WITNESS WHEREOF, Landlord and Tenant have caused this Amendment to be
signed and sealed by their duly authorized signatories under seal as of the day
and year first above written.

                                  LANDLORD:

                                  BUILDING VII ASSOCIATES L.C.
                                  Formerly known as Building VI Associates L.C.

                                  By:                            (SEAL)
                                         -----------------------
                                  Name:
                                         -------------------------------
                                  Title:
                                         -------------------------------

                                  TENANT:

                                  PEC SOLUTIONS, INC.

                                  By:                            (SEAL)
                                         -----------------------
                                  Name:
                                         -------------------------------
                                  Title:
                                         -------------------------------

                                       2<Page>

                                                                       EX. 10.19

                                FIRST AMENDMENT
                                       TO
                          BUILDING VI ASSOCIATES L.C.
                              OPERATING AGREEMENT

      This First Amendment to the Building VI Associates L.C. Operating
Agreement (the "Amendment") is made effective for all purposes as of the 1st day
of May, 2001 (the "Effective Date"), by and among the undersigned parties with
reference to the following:

                                    RECITALS

      A. Building VI Associates L.C. was formed pursuant to the Building VI
Associates L.C. Articles of Organization (the "Articles") filed with the
Virginia State Corporation Commission ("SCC") on February 1, 2001 and the
Building VI Associates L.C. Operating Agreement made effective as of May 7,
2001, (the "Operating Agreement").

      B. Building VI Associates L.C. desires to change its name to Building VII
Associates L.C.

      C. Building VI Associates L.C. has filed an Amendment to Articles of
Organization with the State Corporation Commission on _______________________,
2001 to change its name to Building VII Associates L.C. (the "Company").

      NOW, THEREFORE, in consideration of the recitals and of other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

      1. The foregoing recitals A through C are fully incorporated herein by
this reference as if fully restated herein.

      2. The name of the Company shall be changed to Building VII Associates
L.C. and the Company shall be known as Building VII Associates L.C. from and
after the Effective Date.

      3. This Amendment may be executed by the Members and Manager in separate
counterparts, each of which when so executed and delivered shall be an original,
but all such counterparts together shall constitute one and the same document.
All signatures need not be on the same counterpart.

      4. Except as amended hereby, the Operating Agreement remains unmodified
and in full force and effect.

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      IN WITNESS WHEREOF, the parties have executed this Amendment as of the day
and year first above written.

                                        MEMBERS:

                                        BUILDING VI INVESTMENTS L.C.,
                                        a Virginia limited liability company

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Its:  Manager

                                        PEC SOLUTIONS, INC.,
                                        a Delaware corporation

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Its:
                                            ------------------------------------

                                        MANAGERS:

                                        ----------------------------------------
                                        MILTON V. PETERSON

                                        ----------------------------------------
                                        WILLIAM E. PETERSON

                                        ----------------------------------------
                                        STEVEN B. PETERSON

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