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                                                                    EXHIBIT 10.9

                              SEPARATION AGREEMENT

     This Separation Agreement (the "Agreement") is made this 12th day of June,
2002, by and between Syntroleum Corporation, a Delaware corporation, having an
address of 1350 S. Boulder Avenue, Suite 1100, Tulsa, Oklahoma 74119
("Employer") and Mark A. Agee, having an address of 5535 E. 107th Street, Tulsa,
Oklahoma, 74137, ("Employee").

     WHEREAS, Employee and Employer are parties to a Second Amended and Restated
Employment Agreement made effective June 17, 1999 (the "Employment Agreement") a
copy of which is attached hereto; and

     WHEREAS, Employee and Employer mutually desire to terminate their
employment relationship upon the terms and conditions set forth in this
Agreement,

     NOW, THEREFORE, in consideration of the mutual promises and covenants set
forth in this Agreement, the parties agree as follows:

     1.  Separation From Employment. Employee will terminate his employment with
Employer effective June 1, 2002 (the "Termination Date"). The Employment
Agreement shall terminate effective as of the Termination Date except that the
provisions of Sections 6, 7, 8, 9, 10, 11, 12 and 16 thereof shall survive such
termination and continue in full force and effect in accordance with their
respective terms.

     2.  Payments. In consideration for Employee signing this Agreement,
Employer shall provide employee the following, payments and benefits :

(a)  Employee shall be paid an amount equivalent to his regular salary of
     $19,166.67 per month for the 26 month period commencing on June 1, 2002 and
     ending on July 31, 2004. Employee hereby waives any other payments or
     amounts that would otherwise be due under the terms of any prior agreements
     or understandings. From the amounts paid under this paragraph Employer will
     withhold amounts it deems necessary to ensure the proper payment of all
     taxes and to satisfy the federal, state, or local laws. Prior to payment of
     any amounts under this Agreement Employee shall execute and deliver to
     Employer a W-9 and any other document deemed necessary by the Employer's
     tax advisers to ensure the proper withholding of taxes.

(b)  In the event Employee elects to continue coverage under COBRA, Employer
     shall pay 100% of the major medical insurance premium for the current
     coverage election for the period from August 1, 2002, through January 31,
     2004, or until Employee secures employment providing alternative coverage,
     whichever occurs earlier. Employee will be responsible for any premiums
     applicable to additional elections and coverages. If Employee does not
     secure other employment prior to January 31, 2004, Employer will be
     responsible for 100% of the major medical insurance premiums as set forth
     in paragraph (c) below.

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(c)  Upon expiration of the COBRA coverage as set forth in paragraph (b) above
     and should Employee fail to secure employment providing alternative
     coverage, Employer will be responsible for 100% of the insurance policy
     premiums associated with providing Employee with major medical coverage
     through July 31, 2004 in the form of a policy available to individuals from
     the Employer's then current medical insurance carrier of a type which most
     closely resembles the benefits available to employees of Employer at that
     time.

(d)  Notwithstanding the termination and expiration provisions contained in any
     grant of options to purchase shares of Employer's common stock, all
     currently outstanding stock options granted to Employee shall immediately
     vest and the option exercise period and other terms of such options shall
     be as set forth in the option agreements relating thereto. As further
     clarification, the option exercise periods set forth in the any outstanding
     option period shall not be shortened due to the termination of employment.

(e)  Employer will continue to allow Employee the use of the vehicle which the
     Employer is currently leasing on his behalf or an equivalent replacement
     vehicle through July 31, 2004.

(f)  Employee agrees that (i) he is responsible for any and all taxes associated
     with payments and benefits and (ii) he will seek his own tax advice with
     respect to the deductibility and tax liability associated with the payments
     and benefits provided in connection with this Agreement.

(g)  Employee shall be allowed the use of the a personal computer and cell phone
     in accordance with Employer's policies during the term of his consulting
     engagement.

     3.  Additional Benefits. Nothing contained in this Agreement shall be
interpreted to waive or release Employee's rights under any Employer sponsored
plan in which Employee is a qualified participant, including, but not limited
to, any benefits under a pension or retirement plan. Employee's rights under any
such plan shall be governed by the terms of such plan. Other than the benefits
described in this paragraph, Employee agrees that he is not entitled to any
additional benefits.

     4.  Consulting and Cooperation. Employee agrees to make himself available
to Employer as a consultant during the period commencing June 1, 2002 and ending
May 31, 2004 to consult with Employer at no additional cost to Employer.
Employee also agrees to cooperate with Employer relating to any matters as to
which he was involved while employed by Employer, including any litigation or
administrative actions.

     5.  Resignations. Employee resigns as an officer and as a director of the
Employer and all subsidiary corporations of the Employer effective June 1, 2002.

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     6.  Release of Claims. By signing this Agreement, Employee agrees that the
payments described above are adequate consideration for the release of the
claims described in this Agreement. Employee agrees that he is acting of his own
free will, voluntarily and on behalf of himself, his heirs, administrators,
executors, successors and assigns. Except for the obligations set forth herein,
Employee hereby releases Employer and its predecessors, subsidiaries,
affiliates, directors, officers, employees, and agents, and each of them ("the
Released Parties"), from any and all debts, obligations, claims, demands,
judgments, or causes of action of any kind whatsoever, in tort, contract, by
statute, or on any other basis, for compensatory, punitive, or other damages,
expenses, reimbursements, or costs of any kind, including, but not limited to
any and all claims, demands, rights, and/or causes of action arising out of his
employment with Employer, or relating to any asserted or unasserted employment
discrimination or violations of civil rights such as, but not limited to, those
arising under Title VII of the Civil Rights Act of 1964, the Civil Rights Act of
1991, The Civil Rights Act of 1866 and/or 1871, the Age Discrimination in
Employment Act of 1967 ("ADEA"), the Americans With Disabilities Act of 1990,
Executive Order 11246, the Equal Pay Act of 1963, the Rehabilitation Act of
1973, or any other applicable federal, state, or local employment discrimination
statute or ordinance or any other claim, whether statutory or based on common
law, arising: (1) by reason of his employment with Employer or the termination
of his employment or the circumstances related to the termination; (2) any
claims arising under the Employment Agreement, and/or (3) by reason of any other
matter, cause, or thing whatsoever, from the first date of employment to the
date or execution of this Agreement. Employee agrees and covenants not to
initiate any litigation based on events, occurrences, acts or omissions which
relate in any way to Employee's employment with Employer, the termination
thereof or which are the subject of the releases given herein.

     Age Discrimination Issues. The ADEA is a federal statute prohibiting
discrimination on the basis of age in connection with employment, benefits and
benefit plans. Employee's signature on this Agreement is his acknowledgement
that he understands that he is waiving, releasing and forever giving up all
claims under the ADEA as of the time he signs this Agreement.

     7.  Enforcement. Employee agrees that any breach of Employee's obligations
under this Agreement will cause Employer irreparable injury for which Employer
has no adequate remedy at law. Accordingly, Employee agrees that in the event of
any breach or threatened breach by Employee of Employee's obligations under this
Agreement, Employer shall be entitled, in addition to any and all other remedies
available, to seek and obtain injunctive and/or other equitable relief to
require specific performance of, or to prevent a breach of, Employee's
obligations under this Agreement. Employee agrees that Employer may have such
injunctive relief without posting a bond.

     8.  Representations. Employee represents, warrants and agrees as follows:
(a) no consent of any third party is required in connection with the
transactions contemplated hereby; (b) the provisions hereof will not violate any
court order or ruling; (c) he has the legal right and authority to enter into
and perform his obligations hereunder; and (d) he will indemnify and hold

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Employer harmless for any loss, damage or claim arising from any breach of these
representations or his obligations hereunder.

     9.  Default. If Employee breaches any of the terms of this Agreement,
Employer shall have the right to recover all costs and expenses, including
reasonable attorneys' fees incurred by Employer in enforcing the terms of this
Agreement and/or recovering damages as a result of any such breach.

     10. Severability. If any provision of this Agreement is held invalid or
unenforceable, either in its entirety or by virtue of its scope or application
to given circumstances, such provision shall be deemed modified to the extent
necessary to render the same valid or not applicable to given circumstances, as
the situation may require, and this Agreement shall be construed and enforced as
if such provision had been included herein as so modified in scope or
application or had not been included herein, as the case may be. Although the
Employee agrees that the restrictions on Employee's activities in this Agreement
are reasonable, given the nature and scope of Employer's business, the
information made available to Employee during his employment, and the
compensation provided for herein, Employee and Employer agree that in lieu of
declaring the restrictions void, a court of competent jurisdiction shall be
requested by both parties to modify the restrictions, to the extent necessary
under applicable law, to protect the legitimate interests of both Employer and
Employee.

     11. Denial of Liability. Employer and Employee understand and agree that
the consideration set forth in this Agreement does not constitute an admission
of liability or violation of any applicable law, and any contract provisions or
any rule or regulation, as to which the Released Parties expressly deny
liability.

     12. Entire Agreement. Except for the provisions of the Employment Agreement
which remain in effect as stated herein, and any employment policies regarding
confidentiality and trade secret information, Employee agrees that this
Agreement constitutes the complete agreement between the parties and that no
other representations have been made by Employer.

     13. Death. In the event of Employee's death prior to the final payment
provided for herein, this Agreement shall terminate and Employer shall have no
further obligation hereunder.

     14. Confidentiality. Employee agrees to keep the existence, terms, and
substance of this Agreement confidential and further agrees that he will not
disclose the terms of this Agreement to anyone other than to his attorney and
tax advisors, except as may be required by law.

     15. Interpretation Under State Law. This Agreement shall be construed under
the laws of the State of Oklahoma and shall in all respects be interpreted,
enforced, and governed under the law of said State.

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     16. Review Period. Employee has the right to review this Agreement for a
period of twenty-one days prior to signing. By signing prior to the end of such
twenty-one day period, the Employee is waiving his right to such review period.
Employer has advised Employee that he should seek legal counsel with respect to
this Agreement. Employee also has seven (7) days from the date he signs this
Agreement to revoke the Agreement by providing a written notice to Employer by
contacting Kenneth Agee. Employer will have no obligations under this Agreement
should Employee exercise his right to revoke.

                                           Syntroleum Corporation

                                           By:
                                              ----------------------------------

                                           Title:
                                                 -------------------------------

                                           -------------------------------------
                                           Mark A. Agee

                                           Date:
                                                --------------------------------

                                        5<PAGE>

                                                                   EXHIBIT 10.10

                                 PROMISSORY NOTE
                             MODIFICATION AGREEMENT

     This Promissory Note Modification Agreement (the "Agreement") is made
effective as of June 25, 2002 ("Effective Date") by and between Kenneth L. Agee
("Maker") and Syntroleum Corporation, a Delaware Corporation ("Lender").

     WHEREAS, on June 25, 2001, Lender made certain loans to Maker in the
original amount of $1,100,000 and Maker executed and delivered a Secured
Promissory Note dated June 25, 2001 to Lender (the "Promissory Note");

     WHEREAS, the original due date of the Promissory Note was June 25, 2002;
and

     WHEREAS, the Promissory Note was secured by a security interest and pledge
of shares of the Common Stock of the Lender owned by the Maker pursuant to the
terms of a Security and Stock Pledge Agreement dated June 25, 2001 between
Lender and Maker ("Pledge Agreement"); and

     WHEREAS, Lender has made an additional advances to Maker in the amount of
$341,096.33; and

     WHEREAS, Maker and Lender desire, through this Agreement, to extend the
Promissory Note and to amend certain terms and provisions of the Promissory Note
as set forth below.

     NOW THEREFORE, in consideration of the mutual agreements set forth herein
and other good and valuable consideration, Maker and Lender, for themselves,
their heirs, personal representatives, successors and assigns, hereby agree as
follows:

     1.   Revisions to Note. Maker and Lender agree that the Promissory Note is
          hereby modified in the following respects:

          a.   commencing on the Effective Date, the interest rate under the
               Promissory note is hereby modified to 3.75% per annum.

          b.   the due date of the Promissory Note is hereby modified such that
               the principal and accrued interest will be due and payable on
               June 25, 2003.

          c.   the principal amount of the Promissory Note is hereby modified to
               the sum of $1,460,000.

          d.   In order to reflect the foregoing changes, the first paragraph
               and

          e.   the second paragraph of the Promissory Note are hereby modified
               to read as follows:

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     FOR VALUE RECEIVED, the undersigned, KENNETH L. AGEE ("Maker"), promises to
     pay SYNTROLEUM CORPORATION, a Delaware corporation ("Lender"), at Suite
     1100, 1350 South Boulder, Tulsa, Oklahoma 74119, or such other address as
     Lender may designate, in lawful money of the United States of America in
     same day funds, the lesser of (i) U.S. $1,460,000 or (ii) the then
     outstanding principal amount of each loan (the "Loan" or "Loans") made by
     the Lender from time to time to the Maker hereunder. Principal and accrued
     interest will be due and payable on June 25, 2003. Maker may prepay this
     Note, in part or in full, at any time without penalty as to interest or
     principal.

     Each Loan shall bear interest payable at maturity at a rate of 3.75 % per
annum for each day principal is outstanding under this Note. Interest shall be
computed on the basis of a year of 365 days (or 366 days in a leap year) and
paid for actual days elapsed (including the first day but excluding the last
day).

     2.   Revisions to the Pledge Agreement. The Pledge Agreement is hereby
          modified to reflect the foregoing changes to the Promissory Note and
          is otherwise ratified, affirmed and approved.

     3.   No further changes. Except as expressly amended by this Agreement, the
          Promissory Note and Pledge Agreement are in all respects ratified and
          confirmed and all the terms, provisions, conditions, covenants,
          warranties and agreements set forth and contained therein shall be and
          remain in full force and effect and the lien and priority of the
          Pledge Agreement is hereby ratified and confirmed to the full extent
          of the indebtedness evidenced by the Promissory Note, as herein
          modified.

     In Witness Whereof, the parties have duly executed and delivered this
Agreement as of the effective date.

                                               ---------------------------------
                                               Kenneth L. Agee

                                               Syntroleum Corporation

                                               By
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