Exhibit 4

                             AMENDMENT NO. 3 TO THE
                  HEICO CORPORATION COMBINED STOCK OPTION PLAN

         WHEREAS, on March 16, 1999, the Board of Directors of HEICO Corporation
(the "Board") approved an Amendment to the HEICO Combined Stock Option Plan (the
"Plan") amending Section 9 of the Plan (Exercise of Options);

         NOW THEREFORE, in accordance with the terms of the Plan, the Plan is
hereby amended as follows:

         1.    Section 9 of the HEICO Corporation Combined Stock Option Plan is
         hereby amended to read in its entirety:

               9.    EXERCISE OF OPTIONS. An Option shall be deemed exercised
         when (i) the Company has received written notice of such exercise in
         accordance with the terms of the Option, (ii) full payment of the
         aggregate option price of the Shares as to which the Option is
         exercised has been made, and (iii) arrangements that are satisfactory
         to the Committee in its sole discretion have been made for the
         Optionee's payment to the Company of the amount, if any, that is
         necessary for the Company or Subsidiary employing the Optionee to
         withhold in accordance with applicable Federal or state tax withholding
         requirements. The consideration to be paid for the Shares to be issued
         upon exercise of an Option, as well as the method of payment of the
         exercise price and of any withholding and employment taxes applicable
         thereto, shall be determined by the Committee or the Board and may, in
         the discretion of the Committee or the Board, consist of: (1) cash, (2)
         certified or official bank check, (3) money order, (4) Shares that have
         been held by the Optionee for at least six (6) months (or such other
         Shares, including the withholding of Shares issuable upon exercise of
         the Option, as the Company determines will not cause the Company to
         recognize for a financial accounting purposes a charge for compensation
         expense, (5) pursuant to a "cashless exercise" procedure, by delivery
         of a properly executed exercise notice together with such other
         documentation, and subject to such guidelines, as the Board or the
         Committee shall require to effect an exercise of the Option and
         delivery to the Company by a licensed broker acceptable to the Company
         of proceeds from the sale of Shares or a margin loan sufficient to pay
         the exercise price and any applicable income or employment taxes, (6)
         promissory note, or (7) in such other consideration as the Committee or
         the Board deems appropriate, or by a combination of the above. In the
         case of an Incentive Stock Option, the permissible methods of payment
         shall be specified at the time the Option is granted. The Committee or
         the Board in its sole discretion may accept a personal check in full or
         partial payment of any Shares. If the exercise price is paid in whole
         or in part with Shares, or through the withholding of Shares issuable
         upon exercise of the Option, the value of the Shares surrendered or
         withheld shall be their Fair Market Value on the date the Option is
         exercised. The Company in its sole discretion may, on an individual
         basis or pursuant to a general program established in connection with
         this Plan, lend money to an Optionee, guarantee a loan to an Optionee,
         or otherwise assist an Optionee to obtain



         the cash necessary to exercise all or a portion of an Option granted
         hereunder or to pay any tax liability of the Optionee attributable to
         such exercise. If the exercise price is paid in whole or part with
         Optionee's promissory note, such note shall (i) provide for full
         recourse to the maker, (ii) be collateralized by the pledge of the
         Shares that the Optionee purchases upon exercise of such Option or such
         other collateral as the Board shall require, (iii) bear interest at the
         prime rate of the Company's principal lender, and (iv) contain such
         other terms as the Board in its sole discretion shall reasonably
         require. No Optionee shall be deemed to be a holder of any Shares
         subject to an Option unless and until a stock certificate or
         certificates for such Shares are issued to such person(s) under the
         terms of this Plan. No adjustment shall be made for dividends (ordinary
         or extraordinary, whether in cash, securities or other property) or
         distributions or other rights for which the record date is prior to the
         date such stock certificate is issued, except as expressly provided
         herein.

         2. The effective date of this Amendment No. 3 to the Plan shall be
         March 16, 1999.

         IN WITNESS WHEREOF, HEICO Corporation has caused this Amendment to be
executed this 16th day of March, 1999.

                                       HEICO Corporation

                                       BY:      /s/ LAURANS A. MENDELSON
                                          ------------------------------------
                                       Laurans A. Mendelson
                                       Chairman of the Board, President
                                       and Chief Executive Officer

                                       ATTEST:

                                          /s/ ELIZABETH R. LETENDRE
                                       ---------------------------------------
                                       Elizabeth R. Letendre
                                       Corporate Secretary