Exhibit 99.4  THIRD AMENDMENT TO REIMBURSEMENT, CREDIT AND SECURITY
AGREEMENT AND WAIVER  THIS
THIRD AMENDMENT TO REIMBURSEMENT, CREDIT, AND SECURITY AGREEMENT AND WAIVER
(this Amendment) is made as of this 25th day of July, 2006, by and between INNOVATIVE
SOLUTIONS AND SUPPORT, LLC(the Borrower)
and PNC BANK, NATIONAL ASSOCIATION (the Bank).  RECITALS:  A.The
Bank and the Borrower entered into a Reimbursement, Credit and Security
Agreement dated as of August 1, 2000, as amended by an Amendment dated as
of November 29, 2002 and as further amended by an Amendment dated as of March 20,
2004 (as the same may be amended, restated or further modified and in
effect from time to time, the Agreement), pursuant to which the Bank agreed
to issue a letter of credit for the account of the Borrower in connection with
the issuance of certain industrial development revenue bonds on behalf of
the Borrower.  B.The Borrower has requested the Bank waive
compliance with certain financial covenants and amend certain reporting
requirements and financial covenants in the Agreement and the Bank has agreed
to provide said waiver and amend the Agreement on the terms and subject to the conditions Set forth
herein.  NOW, THEREFORE,in consideration of the foregoing and for good
and valuable consideration, the legality and sufficiency of which is hereby
acknowledged, the parties hereto, intending to be legally bound hereby, agree
as follows:  1.Definitions.  Capitalized
terms used herein and not otherwise defined herein shall have the meanings
assigned to them in the Agreement.  2.Waivers.  The
Borrower has advised the Bank that IS&S, Inc. was in violation of (i) the
total liabilities to EBITDA covenant contained in Section 6.21(a) of
the Agreement, (ii) the Fixed Charge Ratio covenant contained in Section 6.21(b) of the Agreement, and (iii) the
minimum Tangible Net Worth covenant contained in Section 6.21(c) of
the Agreement each as of the end of the fiscal quarter of IS&S, Inc. ending
on June 30, 2006. At the Borrowers request, the Bank hereby waives
IS&S, Incs violation of the covenants contained in Section 6 21(a), Section 6.21(b) and
Section 6.21(c) for the fiscal quarter ending on June 30, 2006 and the resulting Events of Default arising there
from. The foregoing waivers shall not be deemed to operate as or obligate the Bank to grant any future
waiver or modification of the provisions of Section 6.21(a), Section 6.21(b) or
Section 6.21(c) for any other
fiscal period or of any other term, condition or Event of Default under the
Agreement.


3.Amendment to Agreement. The Agreement is
hereby amended effective as of the date hereof as follows:  (a)Section 6.10(a)(1) is
hereby amended and restated to read in full as follows:  (1)audited
consolidated and consolidating financial statements for IS&S, Inc. and
its subsidiaries, including a consolidated balance sheet and related
consolidated statements of income, retained earnings, cash flows, and changes
in financial position as of the end of such Fiscal Year and for such Fiscal
Year, audited by independent certified public accountants acceptable to the
Bank and prepared in accordance with GAAP, which shall fairly present the
consolidated financial condition of IS&S, Inc. and its subsidiaries as at
the end of such Fiscal Year, and  (b)Section 6.21
is hereby amended and restated to read in full as follows:  Section 6.21Financial covenants. The Borrower shall
cause IS&S, Inc. to observe the following covenants:  (a)IS&S, Inc.
will maintain, on a consolidated basis, as of the end of each fiscal quarter of
IS&S, Inc. beginning with the fiscal quarter ending on June 30,
2007, a ratio of total liabilities to EBITDA of not greater than 2.25:1.00.  (b)IS&S, Inc.
will maintain, on a consolidated basis, as of the end of each fiscal quarter of IS&S, Inc.
beginning with the fiscal quarter ending on June 30, 2007, a Fixed Charge
Ratio equal to or greater than 1.25:1.00.  (c)IS&S, Inc.
will maintain, on a consolidated basis, at all times a minimum Tangible Net
Worth of $65,000,000.  4.Amendmentsto theOtherDocuments.  All references to the Agreement in the Collateral
Documents or the Bond Documents and in any documents executed in connection
therewith shall be deemed to refer to the Agreement as amended by this
Amendment.  5.Ratification of the Other
Documents.  Notwithstanding anything to the
contrary herein contained or any claims of the parties to the contrary, the
Bank and the Borrower agree that the Agreement and the Collateral
Documents and each of the documents executed in connection therewith are in full force and effect and each such
document shall remain in full force and effect, as further amended by this Amendment,
and the Borrower hereby ratifies and confirms its obligations thereunder.  6.Representations
and Warranties.  (a)The Borrower hereby
certifies that (i) the representations and warranties of the Borrower in
the Agreement are true and correct in all material respects as of the date
hereof, as if made on the date hereof and (ii) no Event of Default and no event which could
become an  2


Event
of Default withthepassage of time or the giving of notice, or
both, under the Agreement or the Collateral Documents exists on the date hereof.  (b)The Borrower further represents that it has
all the requisite power and authority to enter into and to perform its
obligations under this Amendment, and
that the execution, delivery and performance of this Amendment have been duly
authorized by all requisite action and will not violate or constitute a default
under any provision of any
applicable law, rule, regulation, order, writ, judgment, injunction, decree,
determination or award presently in effect or of the organizational documents
of the Borrower, or of any indenture, note, loan or credit agreement, license
or any other agreement, lease or instrument to which the Borrower is a
party or by which the Borrower or any of its properties is bound.  (c)The Borrower also further represents that the
Borrowers reimbursement obligation under the Agreement is absolute and unconditional, and there exists no right of setoff or recoupment, counterclaim or defense of any
nature whatsoever to payment of such obligations.  7.Conditions Precedent.  The amendments
set forth herein shall be effective as of the date hereof upon the fulfillment,
to the satisfaction of the Bank and its counsel, of the following conditions
precedent:  (a)The Borrower
shall have delivered to the Bank the following, all of which shall be in form and substance satisfactory to the Bank and shall be duly
completed and executed:  (i)a fully executed counterpart of this Amendment, including the Consent of
Guarantors; and  (ii)such additional documents, certificates and
information as the Bank may reasonably request.  (b)The representations and warranties set forth
in the
Agreement shall be true and
correct on and us of the date hereof.  (c)No Event of Default hereunder, and no event
which, with the passage of time or the giving of notice, or both, would become
such an Event of Default shall have occurred and be continuing as of the date
hereof, except for those which are being waived pursuant to Section 2
hereof.  8.No Waiver.  This
Amendment does not and shall not be deemed to constitute a waiver
by the Bank of any Event of Default, or of any event which with the passage of time or the giving of notice or both would constitute an Event of
Default, nor does it obligate the Bank to agree to any further modifications to
the Agreement or the Collateral Documents or constitute a waiver of any of the
Banks other rights or remedies.  9.Release and Indemnity.  (a) Recognizing and in. consideration
of the Banks agreement to the amendments provided herein, the Borrower hereby
waives and releases the Bank and its officers, attorneys, agents, directors,
and employees from any liability, suit,  3


damage,
claim, actions, counterclaims or offsets, loss or expense of any kind or nature
whatsoever and howsoever arising, whether known or unknown and whether based on
facts now known or unknown, direct or derivative, that the Borrower, or anyone
claiming in a derivative capacity from the Borrower, ever had or has as of the
date of this Amendment against any of them including, without limitation, any
of the foregoing arising out of or relating to the Banks or such other Persons
acts or omissions with respect to this Amendment, the other documents executed
in connection herewith, the Agreement, the Collateral Documents, the Bond
Documents or any other matters described or referred to herein or therein.  (b)The Borrower further hereby agrees to
indemnify and hold the Bank and its respective officers, attorneys, agents,
directors and employees harmless from any loss, damage, judgment, liability or
expense (including counsel fees) suffered by or rendered against the Bank or
any of them on account of anything arising out of this Amendment, the
Agreement, the Collateral Documents, the Bond Documents or any other document
or instrument delivered pursuant hereto or thereto up to and including the date
of this Amendment; provided that, the Borrower shall not
have any obligation hereunder to the Bank or such other Person with respect to
indemnified liabilities arising from the gross negligence or willful misconduct
of the Bank or such other Person.  10.Miscellaneous.  (a)All terms, conditions, provisions and
covenants in the Agreement and the Collateral Documents and all other documents
delivered to the Bank in connection therewith shall remain
unaltered and in full force and effect except as modified or amended hereby. To
the extent that any term or provision of this Amendment is or may be deemed
expressly inconsistent with any term or provision in the Agreement or any
Collateral Document or any other document executed in connection therewith, the
terms and provisions hereof shall control.  (b)This Amendment constitutes the entire
agreement of the parties with respect to the subject matter hereof and
supersedes all prior and contemporaneous understandings and agreements.  (c)In the event any provisions of this
Amendment shall be held invalid or unenforceable by any court of competent
jurisdiction, such holding shall not invalidate or render unenforceable any
other provision hereof.  (d)This Amendment shall be
governed by and construed according to the laws of the Commonwealth of
Pennsylvania.  (e)This Amendment, and the Agreement and
Collateral Documents as amended hereby, shall inure to the benefit of, and be
binding upon, the parties hereto and thereto and their respective
successors and assigns and may be executed in one or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.  (f)The headings used in this Amendment are for
convenience of reference only,
do not form a part of this
Amendment and shall not affect in any way the meaning or
interpretation of this Amendment.  4


IN WITNESS WHEREOF, the parties hereto have executed this ThirdAmendment to Reimbursement, Credit and Security Agreement and Waiver as of the day
and year first above written.   INNOVATIVE
  SOLUTIONS AND 
  SUPPORT, LLCBy:
  Innovative
  Solutions and Support, 
  Incorporated, its sole member and 
  managerBy:
  /s/ James ReillyName: James ReillyTitle:   CFOPNC
  BANK, NATIONAL ASSOCIATIONBy:
  /s/ John M DiNapoliName: John
  M DiNapoliTitle:  
  Senior Vice President  S-1


CONSENT OF GUARANTORS  Each
of the undersigned guarantors (the Guarantors) consents to the provisions of
the foregoing Third Amendment to Reimbursement, Credit and Security Agreement
and Waiver (the Amendment) and confirms and agreesthat:(a) such Guarantors obligations under
its Guaranty dated as of August 1, 2000 (as the same may
be amended, restated or further modified and in effect from time to time, the Guaranty),
relating to the obligations of the Borrower to the Bank shall be unimpaired by
the Amendment; (b) such Guarantor has no defenses, set offs,
counterclaims, discounts or charges of any kind against the Bank, its officers,
directors, employees, agents or attorneys with respect to the Guaranty; and (c) all
of the terms, conditions and covenants in the Guaranty remain unaltered and in
full force and effect and are hereby ratified and confirmed and apply to the
obligations of the Borrower to the Bank, as modified by the Amendment. Each of
the Guarantors certifies that all representations and warranties made by it in
the Guaranty are true and correct as of the date of the Amendment.  Each of the Guarantors ratifiesand confirms theindemnification, confessionof judgment and waiver of
jury trial provisions, if any, contained in the Guaranty.  WITNESSthe due execution of
this Consent as a document under seal as of the date of the Amendment,
intending to be legally bound hereby of Guarantors.  INNOVATIVE SOLUTIONS AND 
  SUPPORT, INCORPORATEDBy:
  /s/ James ReillyIS&S DELAWARE, INC.By:
  /s/ James ReillyName: James ReillyTitle:   CFO