Document:

<PAGE>

                                                                     EXHIBIT 4.3

                        SECURED TRANCHE C PROMISSORY NOTE
                        ---------------------------------

$1,500,000                                                      January 29, 2002

      FOR VALUE RECEIVED, ADVANCED AERODYNAMICS & STRUCTURES, INC., a Delaware
corporation (the "Debtor"), hereby unconditionally promises to pay to the order
of CONGRESS FINANCIAL CORPORATION (SOUTHWEST), a Texas corporation (the
"Payee"), at the offices of Payee at 1201 Main Street, Suite 1625, Dallas, Texas
75202, or at such other place as the Payee or any holder hereof may from time to
time designate, the principal sum of ONE MILLION FIVE HUNDRED THOUSAND DOLLARS
($1,500,000) in lawful money of the United States of America and in immediately
available funds, on January 29, 2007 (or earlier in accordance with the terms
and conditions of the Assignment and Assumption Agreement (as hereinafter
defined) and as hereinafter provided) in the amount of the entire unpaid balance
of this Note.

      Debtor hereby further promises to pay interest to the order of Payee on
the unpaid principal balance hereof at the Interest Rate (as hereinafter
defined). Such interest shall be paid in like money at said office or place on
July 1, 2004 and thereafter on the first business day of each calendar quarter
(i.e., January 1, April 1, July 1 and October 1) until the indebtedness
evidenced by this Note is paid in full. Interest on the unpaid balance of
Tranche C during the first thirty (30) months of the term of the Tranche C Note
shall accrue and not be due and payable unless Debtor does not pay when due
(whether on the stated maturity, by acceleration or otherwise) any portion of
principal or interest in respect of the Deferred Purchase Price Obligations (as
hereinafter defined), in which case all of such accrued and unpaid interest
shall become immediately due and payable in accordance with the terms of this
Note and the other Assignment Agreements. Interest payable upon and after an
Event of Default or termination of the Assignment Agreements shall be payable
upon demand.

      For purposes hereof, (a) the term "Interest Rate" shall mean the Prime
Rate; provided, that, at Payee's option, the Interest Rate shall mean a rate of
two (2%) percent per annum in excess of the Prime Rate upon and after an Event
of Default or termination of the Assignment Agreement, (b) the term "Prime Rate"
shall mean the rate from time to time publicly announced by First Union National
Bank, or its successors, at its office in Philadelphia, Pennsylvania, as its
prime rate, whether or not such announced rate is the best rate available at
such bank, (c) the term "Event of Default" shall mean an Event of Default as
such term is defined in the AASI Collateral Assignment of Secured Debt, (d) the
term "Assignment and Assumption Agreement" shall mean the Assignment and
Assumption Agreement, dated of even date herewith, between Debtor and Payee, as
the same now exists or may hereafter be amended, modified, supplemented,
extended, renewed, restated or replaced, (e) the term "AASI Collateral
Assignment of Secured Debt" shall mean the Collateral Assignment of Debt and
Security Agreement, dated of even date herewith, between Debtor and Payee, as
the same now exists or may hereafter be amended, modified, supplemented,
extended, renewed, restated or replaced, and (f) the term "Maximum Interest
Rate" shall mean the maximum non-usurious rate of interest under applicable
Federal or State law

<PAGE>

as in effect from time to time that may be contracted for, taken, reserved,
charged or received in respect of indebtedness of Debtor to Payee. Unless
otherwise defined herein, all capitalized terms used herein shall have the
meaning assigned thereto in the Assignment and Assumption Agreement.

      Interest shall be payable by Debtor to Payee quarterly in arrears not
later than the first day of each calendar quarter and shall be calculated on the
basis of a three hundred sixty (360) day year and actual days elapsed. The
Interest Rate shall increase or decrease by an amount equal to each increase or
decrease in the Prime Rate effective on the first day of the month after any
change in such Prime Rate is announced based on the Prime Rate in effect on the
last day of the month in which any such change occurs. No agreements,
conditions, provisions or stipulations contained in this Note or any of the
other Assignment Agreements or any Event of Default, or the exercise by Payee of
the right to accelerate the payment or the maturity of all or any portion of the
Deferred Purchase Price Obligations, or the exercise by Payee of any option
whatsoever contained in this Note or any of the other Assignment Agreements, or
the prepayment by Debtor of any of the Deferred Purchase Price Obligations, or
the occurrence of any event or contingency whatsoever, shall entitle Payee to
contract for, charge or receive, in any event, interest exceeding the Maximum
Interest Rate. In no event shall Debtor be obligated to pay interest exceeding
such Maximum Interest Rate. All agreements, conditions or stipulations, if any,
which may in any event or contingency whatsoever operate to bind, obligate or
compel Debtor to pay a rate of interest exceeding the Maximum Interest Rate
shall be without binding force or effect, at law or in equity, to the extent of
the excess of interest over such Maximum Interest Rate. In the event any
interest is contracted for, charged or received in excess of the Maximum
Interest Rate ("Excess"), Debtor acknowledges and stipulates that any such
contract, charge or receipt shall be the result of an accident and bona fide
error, and that any Excess received by Payee shall be applied, first, to the
payment of the then outstanding and unpaid principal hereunder; second, to the
payment of the other Deferred Purchase Price Obligations then outstanding and
unpaid; and third, returned to Debtor, it being the intent of the parties hereto
not to enter at any time into a usurious or otherwise illegal relationship.
Debtor recognizes that, with fluctuations in the Interest Rate and the Maximum
Interest Rate, such an unintentional result could inadvertently occur. By the
execution of this Note, Debtor agrees that (a) the credit or return of any
Excess shall constitute the acceptance by Debtor of such Excess, and (b) Debtor
shall not seek or pursue any other remedy, legal or equitable, against Payee,
based in whole or in part upon contracting for, charging or receiving of any
interest in excess of the Maximum Interest Rate. For the purpose of determining
whether or not any Excess has been contracted for, charged or received by Payee,
all interest at any time contracted for, charged or received by Payee in
connection with this Note or any of the other Assignment Agreements shall be
amortized, prorated, allocated and spread during the entire term of this Note in
accordance with the amounts outstanding from time to time hereunder and the
Maximum Interest Rate from time to time in effect in order to lawfully charge
the maximum amount of interest permitted under applicable law.

                                       -2-

<PAGE>

      This Note is issued pursuant to the terms and provisions of the Assignment
and Assumption Agreement to evidence Tranche C of the Deferred Purchase Price
Obligations owed by Payee to Debtor. This Note is secured by the Deferred
Purchase Price Collateral described in the AASI Collateral Assignment of Secured
Debt and all notes, guarantees, security agreements and other agreements,
documents and instruments now or at any time hereafter executed and/or delivered
by Debtor or any other party in connection therewith (all of the foregoing,
together with the Assignment and Assumption Agreement and the AASI Collateral
Assignment of Secured Debt, as the same now exist or may hereafter be amended,
modified, supplemented, renewed, extended, restated or replaced, being
collectively referred to herein as the "Assignment Agreements"), and is entitled
to all of the benefits and rights thereof and of the other Assignment
Agreements. At the time any payment is due hereunder, at its option, Payee may
charge the amount thereof to any account of Debtor maintained by Payee.

      If any payment of principal or interest is not made when due hereunder, or
if any other Event of Default shall occur for any reason, or if the Assignment
Agreements shall be terminated for any reason whatsoever, then and in any such
event, in addition to all rights and remedies of Payee under the Assignment
Agreements, applicable law or otherwise, all such rights and remedies being
cumulative, not exclusive and enforceable alternatively, successively and
concurrently, Payee may, at its option, declare any or all of Debtor's
obligations, liabilities and indebtedness owing to Payee under the Assignment
Agreements (the "Deferred Purchase Price Obligations"), including, without
limitation, all amounts owing under this Note, to be due and payable, whereupon
the then unpaid balance hereof, together with all interest accrued thereon,
shall forthwith become due and payable, together with interest accruing
thereafter at the then applicable Interest Rate stated above until the
indebtedness evidenced by this Note is paid in full, plus the costs and expenses
of collection hereof, including, but not limited to, attorneys' fees and legal
expenses.

      Debtor (i) waives diligence, demand, notice of intent to accelerate,
notice of acceleration, presentment, protest and notice of any kind, (ii) agrees
that it will not be necessary for Payee to first institute suit in order to
enforce payment of this Note and (iii) consents to any one or more extensions or
postponements of time of payment, release, surrender or substitution of
collateral security, or forbearance or other indulgence, without notice or
consent. The pleading of any statute of limitations as a defense to any demand
against Debtor is expressly hereby waived by Debtor. Upon any Event of Default
or termination of the Assignment Agreements, Payee shall have the right, but not
the obligation to setoff against this Note all money owed by Payee to Debtor.

      Payee shall not be required to resort to any Deferred Purchase Price
Collateral for payment, but may proceed against Debtor and any guarantors or
endorsers hereof in such order and manner as Payee may choose. None of the
rights of Payee shall be waived or diminished by any failure or delay in the
exercise thereof.

      The validity, interpretation and enforcement of this Note and the other
Assignment Agreements and any dispute arising in connection herewith or
therewith shall be governed by the internal laws of the State of Texas (without
giving effect to principles of conflict of laws).

                                       -3-

<PAGE>

      Debtor irrevocably consents and submits to the non-exclusive jurisdiction
of the District Court of the State of Texas and the United States District Court
for the Northern District of Texas and waives any objection based on venue or
forum non conveniens with respect to any action instituted therein arising under
this Note or any of the other Assignment Agreements or in any way connected with
or related or incidental to the dealings of Debtor and Payee in respect of this
Note or any of the other Assignment Agreements or the transactions related
hereto or thereto, in each case whether now existing or hereafter arising, and
whether in contract, tort, equity or otherwise, and agrees that any dispute
arising out of the relationship between Debtor and Payee or the conduct of such
persons in connection with this Note or otherwise shall be heard only in the
courts described above (except that Payee shall have the right to bring any
action or proceeding against Debtor or its property in the courts of any other
jurisdiction which Payee deems necessary or appropriate in order to realize on
the Deferred Purchase Price Collateral or to otherwise enforce its rights
against Debtor or its property).

      Debtor hereby waives personal service of any and all process upon it and
consents that all such service of process may be made by certified mail (return
receipt requested) directed to it and service so made shall be deemed to be
completed five (5) days after the same shall have been so deposited in the U.S.
mails, or, at Payee's option, by service upon Debtor in any other manner
provided under the rules of any such courts. Within thirty (30) days after such
service, Debtor shall appear in answer to such process, failing which Debtor
shall be deemed in default and judgment may be entered by Payee against Debtor
for the amount of the claim and other relief requested.

      DEBTOR HEREBY WAIVES ANY RIGHT TO TRIAL BY JURY OF ANY CLAIM, DEMAND,
ACTION OR CAUSE OF ACTION (i) ARISING UNDER THIS NOTE OR (ii) IN ANY WAY
CONNECTED WITH OR RELATED OR INCIDENTAL TO THE DEALINGS BETWEEN DEBTOR AND PAYEE
IN RESPECT OF THIS NOTE OR THE OTHER ASSIGNMENT AGREEMENTS OR THE TRANSACTIONS
RELATED HERETO OR THERETO IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER
ARISING, AND WHETHER IN CONTRACT, TORT, EQUITY OR OTHERWISE. DEBTOR AGREES AND
CONSENTS THAT ANY SUCH CLAIM, DEMAND, ACTION OR CAUSE OF ACTION SHALL BE DECIDED
BY COURT TRIAL WITHOUT A JURY.

      The execution and delivery of this Note has been authorized by the Board
of Directors and by any necessary vote or consent of the stockholders of Debtor.
Debtor hereby authorizes Payee to complete this Note in any particulars
according to the terms of the loan evidenced hereby.

      This Note shall be binding upon the successors and assigns of Debtor and
inure to the benefit of Payee and its successors, endorsees and assigns.
Whenever used herein, the term "Debtor" shall be deemed to include its
successors and assigns and the term "Payee" shall be deemed to include its
successors, endorsees and assigns. If any term or provision of this Note

                                       -4-

<PAGE>

shall be held invalid, illegal or unenforceable, the validity of all other terms
and provisions hereof shall in no way be affected thereby.

WITNESSED BY:                     ADVANCED AERODYNAMICS &
                                  STRUCTURES, INC.
------------------------
                                  By:
                                      -----------------------------------------

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

                                       -5-<PAGE>

                                                                     EXHIBIT 4.4

               LIMITED RECOURSE SECURED TRANCHE D PROMISSORY NOTE

$5,714,408.71                                                   January 29, 2002

      FOR VALUE RECEIVED, ADVANCED AERODYNAMICS & STRUCTURES, INC., a Delaware
corporation (the "Debtor"), hereby unconditionally promises to pay to the order
of CONGRESS FINANCIAL CORPORATION (SOUTHWEST), a Texas corporation (the
"Payee"), at the offices of Payee at 1201 Main Street, Suite 1625, Dallas, Texas
75202, or at such other place as the Payee or any holder hereof may from time to
time designate, the principal sum of FIVE MILLION SEVEN HUNDRED FOURTEEN
THOUSAND FOUR HUNDRED EIGHT DOLLARS AND 71/100 ($5,714,408.71) in lawful money
of the United States of America and in immediately available funds on January
29,2007 (or earlier in accordance with the terms and conditions of the
Assignment and Assumption Agreement (as hereinafter defined and as hereinafter
provided); provided, that, if Debtor first repays all of the Deferred Purchase
Price Obligations (as hereinafter defined) in respect of the AASI Secured Notes
(as defined in the Assignment and Assumption Agreement), other than this Note,
then all Deferred Purchase Price Obligations evidenced by this Note shall
automatically be deemed paid in full and all such indebtedness including any
accrued but unpaid interest shall be cancelled.

      All principal and interest shall be due and payable Debtor does not pay
when due (whether on the stated maturity, by acceleration or otherwise) any
portion of principal or interest in respect of the Deferred Purchase Price
Obligations (as hereinafter defined), in which case all of such accrued and
unpaid interest shall become immediately due and payable in accordance with the
terms of this Note and the other Assignment Agreements. Interest on the unpaid
principal balance of this Note shall accrue at the Interest Rate (as hereinafter
defined) but shall not be due and payable unless Debtor does not pay when due
(whether on the stated maturity, by acceleration or otherwise) any portion of
principal or interest in respect of the Deferred Purchase Price Obligations.

      For purposes hereof, (a) the term "Interest Rate" shall mean the Prime
Rate; provided, that, at Payee's option, the Interest Rate shall mean a rate of
two (2%) percent per annum in excess of the Prime Rate upon and after an Event
of Default or termination of the Assignment Agreement, (b) the term "Prime Rate"
shall mean the rate from time to time publicly announced by First Union National
Bank, or its successors, at its office in Philadelphia, Pennsylvania, as its
prime rate, whether or not such announced rate is the best rate available at
such bank, (c) the term "Event of Default" shall mean an Event of Default as
such term is defined in the AASI Collateral Assignment of Secured Debt, (d) the
term "Assignment and Assumption Agreement" shall mean the Assignment and
Assumption Agreement, dated of even date herewith, between Debtor and Payee, as
the same now exists or may hereafter be amended, modified, supplemented,
extended, renewed, restated or replaced, (e) the term "AASI Collateral
Assignment of Secured Debt" shall mean the Collateral Assignment of Debt and
Security Agreement, dated of even date herewith, between Debtor and Payee, as
the same now exists or may hereafter be amended, modified,

<PAGE>

supplemented, extended, renewed, restated or replaced, and (f) the term "Maximum
Interest Rate" shall mean the maximum non-usurious rate of interest under
applicable Federal or State law as in effect from time to time that may be
contracted for, taken, reserved, charged or received in respect of indebtedness
of Debtor to Payee. Unless otherwise defined herein, all capitalized terms used
herein shall have the meaning assigned thereto in the Assignment and Assumption
Agreement.

      Interest shall be payable by Debtor to Payee quarterly in arrears not
later than the first day of each calendar quarter and shall be calculated on the
basis of a three hundred sixty (360) day year and actual days elapsed. The
Interest Rate shall increase or decrease by an amount equal to each increase or
decrease in the Prime Rate effective on the first day of the month after any
change in such Prime Rate is announced based on the Prime Rate in effect on the
last day of the month in which any such change occurs. No agreements,
conditions, provisions or stipulations contained in this Note or any of the
other Assignment Agreements or any Event of Default, or the exercise by Payee of
the right to accelerate the payment or the maturity of all or any portion of the
Deferred Purchase Price Obligations, or the exercise by Payee of any option
whatsoever contained in this Note or any of the other Assignment Agreements, or
the prepayment by Debtor of any of the Deferred Purchase Price Obligations, or
the occurrence of any event or contingency whatsoever, shall entitle Payee to
contract for, charge or receive, in any event, interest exceeding the Maximum
Interest Rate. In no event shall Debtor be obligated to pay interest exceeding
such Maximum Interest Rate. All agreements, conditions or stipulations, if any,
which may in any event or contingency whatsoever operate to bind, obligate or
compel Debtor to pay a rate of interest exceeding the Maximum Interest Rate
shall be without binding force or effect, at law or in equity, to the extent of
the excess of interest over such Maximum Interest Rate. In the event any
interest is contracted for, charged or received in excess of the Maximum
Interest Rate ("Excess"), Debtor acknowledges and stipulates that any such
contract, charge or receipt shall be the result of an accident and bona fide
error, and that any Excess received by Payee shall be applied, first, to the
payment of the then outstanding and unpaid principal hereunder; second, to the
payment of the other Deferred Purchase Price Obligations then outstanding and
unpaid; and third, returned to Debtor, it being the intent of the parties hereto
not to enter at any time into a usurious or otherwise illegal relationship.
Debtor recognizes that, with fluctuations in the Interest Rate and the Maximum
Interest Rate, such an unintentional result could inadvertently occur. By the
execution of this Note, Debtor agrees that (a) the credit or return of any
Excess shall constitute the acceptance by Debtor of such Excess, and (b) Debtor
shall not seek or pursue any other remedy, legal or equitable, against Payee,
based in whole or in part upon contracting for, charging or receiving of any
interest in excess of the Maximum Interest Rate. For the purpose of determining
whether or not any Excess has been contracted for, charged or received by Payee,
all interest at any time contracted for, charged or received by Payee in
connection with this Note or any of the other Assignment Agreements shall be
amortized, prorated, allocated and spread during the entire term of this Note in
accordance with the amounts outstanding from time to time hereunder and the
Maximum Interest Rate from time to time in effect in order to lawfully charge
the maximum amount of interest permitted under applicable law.

                                       -2-

<PAGE>

      This Note is issued pursuant to the terms and provisions of the Assignment
and Assumption Agreement to evidence Tranche D of the Deferred Purchase Price
Obligations owed by Payee to Debtor. This Note is secured by the Deferred
Purchase Price Collateral described in the AASI Collateral Assignment of Secured
Debt and all notes, guarantees, security agreements and other agreements,
documents and instruments now or at any time hereafter executed and/or delivered
by Debtor or any other party in connection therewith (all of the foregoing,
together with the Assignment and Assumption Agreement and the AASI Collateral
Assignment of Secured Debt, as the same now exist or may hereafter be amended,
modified, supplemented, renewed, extended, restated or replaced, being
collectively referred to herein as the "Assignment Agreements"), and is entitled
to all of the benefits and rights thereof and of the other Assignment
Agreements. At the time any payment is due hereunder, at its option, Payee may
charge the amount thereof to any account of Debtor maintained by Payee.

      If any payment of principal or interest is not made when due hereunder, or
if any other Event of Default shall occur for any reason, or if the Assignment
Agreements shall be terminated for any reason whatsoever, then and in any such
event, in addition to all rights and remedies of Payee under the Assignment
Agreements, applicable law or otherwise, all such rights and remedies being
cumulative, not exclusive and enforceable alternatively, successively and
concurrently, Payee may, at its option, declare any or all of Debtor's
obligations, liabilities and indebtedness owing to Payee under the Assignment
Agreements (the "Deferred Purchase Price Obligations"), including, without
limitation, all amounts owing under this Note, to be due and payable, whereupon
the then unpaid balance hereof, together with all interest accrued thereon,
shall forthwith become due and payable, together with interest accruing
thereafter at the then applicable Interest Rate stated above until the
indebtedness evidenced by this Note is paid in full, plus the costs and expenses
of collection hereof, including, but not limited to, attorneys' fees and legal
expenses.

      Debtor (i) waives diligence, demand, notice of intent to accelerate,
notice of acceleration, presentment, protest and notice of any kind, (ii) agrees
that it will not be necessary for Payee to first institute suit in order to
enforce payment of this Note and (iii) consents to any one or more extensions or
postponements of time of payment, release, surrender or substitution of
collateral security, or forbearance or other indulgence, without notice or
consent. The pleading of any statute of limitations as a defense to any demand
against Debtor is expressly hereby waived by Debtor. Upon any Event of Default
or termination of the Assignment Agreements, Payee shall have the right, but not
the obligation to setoff against this Note all money owed by Payee to Debtor.

         Payee agrees that Debtor's obligation, liability and indebtedness
hereunder for the Deferred Purchase Price Obligations consisting of Tranche D
shall be limited to the value of the Deferred Purchase Price Collateral, and the
enforcement of Payee's rights and remedies in respect of such obligation,
liability and indebtedness of Debtor shall be limited to the Deferred Purchase
Price Collateral. Upon the occurrence of any Event of Default, Payee may
collect, realize upon, sell or take any other enforcement action pursuant to the
AASI Collateral Assignment of Secured Debt or the other Assignment Agreements
with respect to the Deferred Purchase Price Collateral

                                       -3-

<PAGE>

or any portion thereof. None of the rights of Payee shall be waived or
diminished by any failure or delay in the exercise thereof.

      The validity, interpretation and enforcement of this Note and the other
Assignment Agreements and any dispute arising in connection herewith or
therewith shall be governed by the internal laws of the State of Texas (without
giving effect to principles of conflict of laws).

      Debtor irrevocably consents and submits to the non-exclusive jurisdiction
of the District Court of the State of Texas and the United States District Court
for the Northern District of Texas and waives any objection based on venue or
forum non conveniens with respect to any action instituted therein arising under
this Note or any of the other Assignment Agreements or in any way connected with
or related or incidental to the dealings of Debtor and Payee in respect of this
Note or any of the other Assignment Agreements or the transactions related
hereto or thereto, in each case whether now existing or hereafter arising, and
whether in contract, tort, equity or otherwise, and agrees that any dispute
arising out of the relationship between Debtor and Payee or the conduct of such
persons in connection with this Note or otherwise shall be heard only in the
courts described above (except that Payee shall have the right to bring any
action or proceeding against Debtor or its property in the courts of any other
jurisdiction which Payee deems necessary or appropriate in order to realize on
the Collateral or to otherwise enforce its rights against Debtor or its
property).

      Debtor hereby waives personal service of any and all process upon it and
consents that all such service of process may be made by certified mail (return
receipt requested) directed to it and service so made shall be deemed to be
completed five (5) days after the same shall have been so deposited in the U.S.
mails, or, at Payee's option, by service upon Debtor in any other manner
provided under the rules of any such courts. Within thirty (30) days after such
service, Debtor shall appear in answer to such process, failing which Debtor
shall be deemed in default and judgment may be entered by Payee against Debtor
for the amount of the claim and other relief requested.

      DEBTOR HEREBY WAIVES ANY RIGHT TO TRIAL BY JURY OF ANY CLAIM, DEMAND,
ACTION OR CAUSE OF ACTION (i) ARISING UNDER THIS NOTE OR (ii) IN ANY WAY
CONNECTED WITH OR RELATED OR INCIDENTAL TO THE DEALINGS BETWEEN DEBTOR AND PAYEE
IN RESPECT OF THIS NOTE OR THE OTHER ASSIGNMENT AGREEMENTS OR THE TRANSACTIONS
RELATED HERETO OR THERETO IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER
ARISING, AND WHETHER IN CONTRACT, TORT, EQUITY OR OTHERWISE. DEBTOR AGREES AND
CONSENTS THAT ANY SUCH CLAIM, DEMAND, ACTION OR CAUSE OF ACTION SHALL BE DECIDED
BY COURT TRIAL WITHOUT A JURY.

      The execution and delivery of this Note has been authorized by the Board
of Directors and by any necessary vote or consent of the stockholders of Debtor.
Debtor hereby authorizes Payee to complete this Note in any particulars
according to the terms of the loan evidenced hereby.

                                       -4-

<PAGE>

      This Note shall be binding upon the successors and assigns of Debtor and
inure to the benefit of Payee and its successors, endorsees and assigns.
Whenever used herein, the term "Debtor" shall be deemed to include its
successors and assigns and the term "Payee" shall be deemed to include its
successors, endorsees and assigns. If any term or provision of this Note shall
be held invalid, illegal or unenforceable, the validity of all other terms and
provisions hereof shall in no way be affected thereby.

WITNESSED BY:                  ADVANCED AERODYNAMICS & STRUCTURES, INC.

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

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

                                       -5-

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