THIRD AMENDMENT
                                TO REVOLVING NOTE

      THIS THIRD AMENDMENT TO REVOLVING NOTE ("Third Amendment"), made as of
January 24, 2001, by and among United Industrial Corporation, a Delaware
corporation, having an address of 570 Lexington Avenue, New York, New York
10022, and AAI Corporation, AAI Engineering Support, Inc., AAI/ACL Technologies,
Inc., AAI/ACL Technologies Europe Limited, Detroit Stoker Company, Midwest
Metallurgical Laboratory, Inc., and AAI MICROFLITE Simulation International
Corporation (collectively, the "Borrower"), and First Union Commercial
Corporation, a North Carolina Corporation (the "Lender").

                                    RECITALS

      A.    United Industrial Corporation and certain of its subsidiaries
            entered into a Revolving Note, dated as of June 11, 1997, in the
            maximum principal amount of Seventeen Million, Five Hundred Thousand
            Dollars ($17,500,000.00) made payable to the order of First Union
            Commercial Corporation, as amended by First Amendment to Revolving
            Note, dated as of March 31, 2000 and as further amended by a Second
            Amendment to Revolving Note, dated as of November 14, 2000 (the
            "Revolving Note").

      B.    The Revolving Note evidences Borrower's obligations to repay
            advances of principal made by the Lender under a Revolving Line of
            Credit Loan Agreement Term Loan Agreement and Security Agreement,
            dated June 11, 1997, as amended by that certain First Amendment to
            Revolving Line of Credit Loan Agreement, Term Loan Agreement and
            Security Agreement dated as of October 1, 1998, and by that certain
            Second Amendment to Revolving Line of Credit Loan Agreement Term
            Loan Agreement and Security Agreement dated as of December 31, 1998,
            and by that certain Third Amendment to Revolving Line of Credit Loan
            Agreement, Term Loan Agreement and Security Agreement, made as of
            March 31, 2000, and by that certain Fourth Amendment to Revolving
            Line of Credit Loan Agreement, Term Loan Agreement and Security
            Agreement, dated as of September 21, 2000, and by that certain Fifth
            Amendment to Revolving Line of Credit Loan Agreement, Term Loan
            Agreement and Security Agreement, dated as of November 14, 2000, and
            by that certain Sixth Amendment to Revolving Line of Credit Loan
            Agreement, Term Loan Agreement and Security Agreement, of even date
            herewith (the "Loan Agreement"). The Revolving Note is governed, in
            part, by certain provisions of the Loan Agreement.

      C.    The Borrower and the Lender desire to amend the Revolving Note for
            the purpose of increasing the principal amount of the Revolving Note
            and for certain other purposes hereinafter set forth.




                                   AGREEMENTS

      NOW, THEREFORE, in consideration of the premises, the mutual agreements
herein contained, and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Borrower and the Lender hereby
agree as follows:

1.    Capitalized terms used in this Third Amendment but not defined herein have
      the meanings ascribed to them in the Revolving Note.

2.    The maximum principal sum owing under the Revolving Note is hereby
      modified and increased from Seventeen Million, Five Hundred Thousand
      Dollars ($17,500,000.00) to Twenty Five Million Three Hundred Forty Two
      Thousand and 00/100 Dollars ($25,342,000.00) (the "Principal Sum"), or so
      much thereof as has been or may be advanced or readvanced to or for the
      account of the Borrower pursuant to the terms and conditions of the Loan
      Agreement, together with interest thereon at the rate or rates set forth
      in the Revolving Note.

3.    Except as modified by this Third Amendment, the Revolving Note remains in
      full force and effect and unmodified. Borrower warrants and represents
      that it has no offsets or defenses to its obligations under the Revolving
      Note, as modified by this Third Amendment.

4.    In consideration of Lender's agreement to this Third Amendment, the
      Borrower hereby releases and waives any and all claims of any kind that it
      may have against the Lender as of the date of this Third Amendment arising
      out of or relating to the Loan Agreement or the Revolving Note, as amended
      by this Third Amendment.

5.    ARBITRATION. UPON DEMAND OF ANY PARTY HERETO, WHETHER MADE BEFORE OR AFTER
      INSTITUTION OF ANY JUDICIAL PROCEEDING, ANY CONTROVERSY OR CLAIM ARISING
      OUT OF OR RELATING TO THE LOAN DOCUMENTS BETWEEN PARTIES HERETO (A
      "DISPUTE") SHALL BE RESOLVED BY BINDING ARBITRATION CONDUCTED UNDER AND
      GOVERNED BY THE COMMERCIAL FINANCIAL DISPUTES ARBITRATION RULES (THE
      "ARBITRATION RULES") OF THE AMERICAN ARBITRATION ASSOCIATION ("AAA") AND
      THE FEDERAL ARBITRATION ACT. DISPUTES MAY INCLUDE, WITHOUT LIMITATION,
      TORT CLAIMS, COUNTERCLAIMS, A DISPUTE AS TO WHETHER A MATTER IS SUBJECT TO
      ARBITRATION, CLAIMS BROUGHT AS CLASS ACTIONS, OR CLAIMS ARISING FROM
      DOCUMENTS EXECUTED IN THE FUTURE. A JUDGMENT UPON THE AWARD MAY BE ENTERED
      IN ANY COURT HAVING JURISDICTION. NOTWITHSTANDING THE FOREGOING, THIS
      ARBITRATION PROVISION DOES NOT APPLY TO DISPUTES UNDER OR RELATED TO SWAP
      AGREEMENTS. ALL ARBITRATION HEARINGS SHALL BE CONDUCTED IN THE CITY OR
      COUNTY WHERE THE LENDER'S OFFICE, AS FIRST STATED ABOVE, IS


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      LOCATED, OR AT SUCH OTHER PLACE AS THE PARTIES MAY IN WRITING AGREE. A
      HEARING SHALL BEGIN WITHIN 90 DAYS OF DEMAND FOR ARBITRATION AND ALL
      HEARINGS SHALL CONCLUDE WITHIN 120 DAYS OF DEMAND FOR ARBITRATION. THESE
      TIME LIMITS MAY NOT BE EXTENDED UNLESS A PARTY SHOWS CAUSE FOR EXTENSION
      AND THEN FOR NO MORE THAN A TOTAL OF 60 DAYS. THE EXPEDITED PROCEDURES SET
      FORTH IN RULE 51, ET SEQ., OF THE ARBITRATION RULES SHALL APPLY TO
      DISPUTES IN WHICH THE CLAIM IS LESS THAN $1,000,000.00. ARBITRATORS SHALL
      BE LICENSED ATTORNEYS SELECTED FROM THE COMMERCIAL FINANCIAL DISPUTE
      ARBITRATION PANEL OF THE AAA. THE PARTIES DO NOT WAIVE APPLICABLE FEDERAL
      OR STATE SUBSTANTIVE LAW EXCEPT AS PROVIDED HEREIN. NOTWITHSTANDING THE
      PRECEDING BINDING ARBITRATION PROVISIONS, THE PARTIES AGREE TO PRESERVE
      WITHOUT DIMINUTION, CERTAIN REMEDIES THAT ANY PARTY MAY EXERCISE BEFORE OR
      AFTER AN ARBITRATION PROCEEDING IS BROUGHT. THE PARTIES SHALL HAVE THE
      RIGHT TO PROCEED IN ANY COURT OF PROPER JURISDICTION OR BY SELF HELP TO
      EXERCISE OR PROSECUTE THE FOLLOWING REMEDIES, AS APPLICABLE: (1) ALL
      RIGHTS TO FORECLOSE AGAINST ANY REAL OR PERSONAL PROPERTY OR OTHER
      SECURITY BY EXERCISING A POWER OF SALE OR UNDER APPLICABLE LAW BY JUDICIAL
      FORECLOSURE INCLUDING A PROCEEDING TO CONFIRM THE SALE; (2) ALL RIGHTS OF
      SELF HELP, INCLUDING WITHOUT LIMITATION, PEACEFUL OCCUPATION OF REAL
      PROPERTY AND COLLECTION OF RENTS, SETOFF, AND PEACEFUL POSSESSION OF
      PERSONAL PROPERTY; (3) OBTAINING PROVISIONAL OR ANCILLARY REMEDIES
      INCLUDING INJUNCTIVE RELIEF, SEQUESTRATION, GARNISHMENT, ATTACHMENT,
      APPOINTMENT OF RECEIVER AND FILING AN INVOLUNTARY BANKRUPTCY PROCEEDING;
      AND (4) WHEN APPLICABLE, A JUDGMENT BY CONFESSION OF JUDGMENT. ANY CLAIM
      OR CONTROVERSY WITH REGARD TO ANY PARTY'S ENTITLEMENT TO SUCH REMEDIES IS
      A DISPUTE. THE PARTIES AGREE THAT THEY SHALL NOT HAVE A REMEDY OF PUNITIVE
      OR EXEMPLARY DAMAGES AGAINST OTHER PARTIES IN ANY DISPUTE, AND THEY HEREBY
      WAIVE ANY RIGHT OR CLAIM TO PUNITIVE OR EXEMPLARY DAMAGES THEY MAY NOW
      HAVE OR WHICH MAY ARISE IN THE FUTURE IN CONNECTION WITH ANY DISPUTE
      WHETHER THE DISPUTE IS RESOLVED BY ARBITRATION OR JUDICIALLY.

6.    Lender has executed this Third Amendment for the sole purpose of
      evidencing its consent hereto, and not for the purpose of becoming liable
      on the Revolving Note as a co-maker, endorser or guarantor.

7.    This Third Amendment may be signed in several counterparts which, when
      executed, shall constitute a single agreement. A counterpart containing a
      facsimile signature shall be effective to the same extent as if it were a
      counterpart containing an original signature,


                                       3


      but shall be confirmed promptly with a counterpart containing an original
      signature.


BORROWER:                           UNITED INDUSTRIAL CORPORATION


                                    By  /s/ James Perry
                                       ---------------------------------
                                          James Perry, Vice President


                                    AAI CORPORATION


                                    By  /s/ James Perry
                                       ---------------------------------
                                          James Perry, Vice President


                                    AAI ENGINEERING SUPPORT, INC.


                                    By: /s/ Richard Erkeneff
                                       ---------------------------------
                                         Richard Erkeneff, President


                                    AAI/ACL TECHNOLOGIES, INC.


                                    By: /s/ Thomas E. Wurzel
                                       ---------------------------------
                                          Thomas E. Wurzel, President


                                    AAI/ACL TECHNOLOGIES EUROPE LIMITED


                                    By: /s/ Thomas E. Wurzel
                                       ---------------------------------
                                          Thomas E. Wurzel, President


                                    DETROIT STOKER COMPANY


                                    By  /s/ James Perry
                                       ---------------------------------
                                          James Perry, Vice President


                                       4


                                    MIDWEST METALLURGICAL LABORATORY,
                                    INC.


                                    By: /s/ James Perry
                                       ---------------------------------
                                          James Perry, Vice President


                                    AAI MICROFLITE Simulation International
                                    Corporation


                                    By: /s/ Stanley J. Mecinski, Jr.
                                       ---------------------------------
                                          Stanley J. Mecinski, Jr.
                                          Assistant Secretary and Assistant
                                          Treasurer


CONSENTED TO:                       FIRST UNION COMMERCIAL CORPORATION


                                    By: /s/ Barbara Van Meerten
                                       ----------------------------------------
                                          Barbara Van Meerten, Vice President


STATE OF MARYLAND        )
COUNTY/CITY OF HARTFORD  )To Wit:

      I Diane Richardson, a Notary Public in and for the jurisdiction
aforesaid, do certify that James Perry, whose name is signed to the writing
above, bearing date as of January 26, 2001, as Vice President of United
Industrial Corporation, Vice President of AAI Corporation, Vice President of
Detroit Stoker Company, and Vice President of Midwest Metallurgical Laboratory,
Inc., has acknowledged the same before me in my jurisdiction aforesaid.

      Given under my hand and seal this 26th day of January, 2001.

                                          /s/ Diane Richardson
                                          --------------------
                                          Notary Public

My Commission Expires: September 28, 2004


                                       5


STATE OF MARYLAND        )
COUNTY/CITY OF HARTFORD  )To Wit:

      I Diane Richardson, a Notary Public in and for the jurisdiction aforesaid,
do certify that Richard Erkeneff, whose name is signed to the writing above,
bearing date as of January 26, 2001, as President of AAI Engineering Support,
Inc., has acknowledged the same before me in my jurisdiction aforesaid.

      Given under my hand and seal this 26th day of January, 2001.

                                          /s/ Diane Richardson
                                          --------------------
                                          Notary Public

My Commission Expires: September 28, 2004


STATE OF MARYLAND        )
COUNTY/CITY OF HARTFORD  )To Wit:

      I Diane Richardson, a Notary Public in and for the jurisdiction
aforesaid, do certify that Thomas E. Wurzel, whose name is signed to the writing
above, bearing date as of January 26, 2001, as President of AAI/ACL
Technologies, Inc., and President of AAI/ACL Technologies Europe Limited has
acknowledged the same before me in my jurisdiction aforesaid.

      Given under my hand and seal this 26th day of January, 2001.

                                          /s/ Diane Richardson
                                          --------------------
                                          Notary Public

My Commission Expires: September 28, 2004


STATE OF MARYLAND        )
COUNTY/CITY OF HARTFORD  )To Wit:

      I Diane Richardson, a Notary Public in and for the jurisdiction
aforesaid, do certify that Stanley J. Mecinski, Jr., whose name is signed to the
writing above, bearing date as of January 26, 2001, as Assistant Secretary and
Assistant Treasurer of AAI MICROFLITE Simulation International Corporation has
acknowledged the same before me in my jurisdiction aforesaid.

      Given under my hand and seal this 26th day of January, 2001.

                                          /s/ Diane Richardson
                                          --------------------
                                          Notary Public

My Commission Expires: September 28, 2004


                                       6