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                                                                    EXHIBIT 10dd

                        INCENTIVE STOCK OPTION AGREEMENT
                                      FOR
                  OPTIONEE OF RESTATED 1991 STOCK OPTION PLAN

         This Agreement is made as of the 6th day of December, 1999, between
AIRPORT SYSTEMS INTERNATIONAL, INC., a Kansas corporation (the "Company"), and
KARL GEMPERLI, an employee to the Company or any Subsidiary ("Optionee").

         1.       BACKGROUND. In order to attract and retain the best available
personnel for positions of substantial responsibility in the Company or any
Subsidiary and to promote the success of the Company's business, the Company
has adopted the Restated 1991 Stock Option Plan (the "Plan"), a copy of which
is attached hereto as Exhibit A. Pursuant to the Plan certain Employees and
Consultants of the Company or any Subsidiary may be designated by the Board of
Directors of the Company to receive an option to purchase shares of Common
Stock of the Company ("Common Stock"). Capitalized terms used herein and
otherwise not defined have the meaning ascribed to them in the Plan.

         2.       GRANT OF OPTION. The Company hereby grants to Optionee an
option to purchase up to an aggregate of 50,000 Shares of Common Stock of the
Company (the "Option Shares"), in accordance with the vesting schedule set
forth in Section 3 hereof (the "Option"); provided however, that the Option is
subject to the terms of the Plan and the Stock Transfer Restriction Agreement
for Exercise of Stock Option attached hereto as Exhibit B ("Stock Restriction
Agreement"), the provisions of which are incorporated herein by reference and
the terms of which shall control in the event of any conflict with the terms
hereof. The Option hereby granted is an Incentive Stock Option.

         3.       VESTING OF SHARES. The option to purchase shares of Common
Stock shall cumulatively vest and be exercisable for 10,000 shares of Common
Stock on December 6, 2000, 10,000 shares of Common Stock on December 6, 2001,
10,000 shares of Common Stock on December 6, 2003, 10,000 shares of Common
Stock on December 6, 2004, and 10,000 shares of Common Stock on December 6,
2005; provided, however, that the unvested portions of the Options shall vest
and be exercisable immediately prior to any of the following transactions: (i)
the closing of the Company's sale of all or substantially all of its assets or
(ii) the acquisition of the Company by another entity by means of a merger or
consolidation resulting in the exchange of the outstanding shares of Company's
capital stock for securities or consideration issued or caused to be issued by
the acquiring entity or its subsidiary or (iii) the acquisition from one or
more of the shareholders of the Company of more than fifty percent (50%) of the
Common Stock by a single person or group of persons acting together
(collectively, a "Change in Control Transaction"); provided further, however,
that if the Change in Control Transaction is with any person who is a holder of
Common Stock on the date hereof, or an entity under the control of such person
through stock ownership or otherwise, the unvested portion of the options shall
not vest and the


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options shall remain in effect to vest in accordance with the vesting schedule
set forth in this Section 3.

         4.       EXERCISE OF OPTION

         (a)      An Option shall be deemed to be exercised when the Optionee or
other authorized person gives to the Company written notice of such exercise
and full payment for the Option Shares with respect to which the Option is
exercised has been received by the Company. As a condition to the exercise of
an Option, the Company will require the Optionee to execute a Stock Restriction
Agreement.

         (b)      Until the issuance (as evidenced by the appropriate entry on
the books of the Company or of a duly authorized transfer agent of the Company)
of the stock certificate evidencing such Option Shares, no right to vote or
receive dividends or any other rights as a shareholder shall exist with respect
to the Option Shares, notwithstanding the exercise of the Option. The Company
shall issue (or cause to be issued) such stock certificates promptly upon
exercise of the Option. No adjustment will be made for a dividend or other
right for which the record date is prior to the date of the stock certificate
is issued, except as provided in Section 12 of the Plan.

         (c)      Exercise of an Option in any manner shall result in a decrease
in the number of Option Shares that thereafter may be available, both for
purposes of the Plan and for sale under the Option, by the number of Option
Shares as to which the Option is exercised.

         5.       EXERCISE PRICE AND CONSIDERATION.

         (a)      EXERCISE PRICE. The per Share exercise price for the Option
Shares to be issued pursuant to exercise of an Option shall be two and
one-quarter dollars ($2.25), which is equal to the closing price per share of
the Common Stock on the date hereof as listed on the NASDAQ National Market
System as reported in The Wall Street Journal.

         (b)      FORM OF CONSIDERATION. The consideration to be paid for the
Option Shares to be issued upon exercise of an Option, including the method of
payment, shall be determined by the Board of Directors and may consist entirely
of cash, check, other shares of Common Stock having a fair market value on the
date of surrender equal to the aggregate exercise price of the Option Shares as
to which said option shall be exercised, or any combination of such methods of
payment, or such other consideration and method of payment for the issuance of
Option Shares to the extent permitted under the laws of the state of
incorporation of the Company. In making its determination as to the type of
consideration to accept, the Board of Directors shall consider if acceptance of
such consideration may be reasonably expected to benefit the Company.

         (c)      FAIR MARKET VALUE. The fair market value of shares of Common
Stock delivered to the Company as payment of the purchase price upon exercise
of an Option shall be determined by the Board in its discretion; provided,
however, that where there is a public market for the Common Stock, the fair
market value per share of Common Stock shall be the mean of the bid and asked
prices (or the closing price per


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share if the Common Stock is listed on the National Association of Securities
Dealers Automated Quotation ("NASDAQ") National Market System) of the Common
Stock for the date of grant, as reported in The Wall Street Journal (or, if not
so reported, as otherwise reported by the NASDAQ System) or, if the Common
Stock is listed on a stock exchange, the fair market value per share shall be
the closing price on such exchange on the date of grant of the Option, as
reported in The Wall Street Journal.

         6.       TERM OF OPTION.

         (a)      GENERAL RULE. Except as provided in Section 6(b) and Section
6(c) hereof and in Section 10 and Section 12 of the Plan, the term of each
Option granted pursuant to Section 2 hereof shall be ten (10) years from the
date hereof.

         (b)      EMPLOYMENT OF OPTIONEE TERMINATED. Notwithstanding anything
provided to the contrary in the Plan, if Optionee's employment with the Company
or any Subsidiary is terminated by the Company or any Subsidiary (i) for fraud
or dishonesty of Optionee in connection with fulfillment of his duties and
responsibilities as an employee of the Company or any Subsidiary, including
without limitation, embezzlement of Company or Subsidiary funds; or (ii)
because employee is charged with a felony under any applicable criminal code or
statute, or (iii) if Optionee quits the employment of the Company or any
Subsidiary, then all unexercised Options, whether vested or unvested, shall
terminate immediately upon such termination of employment. If Optionee's
employment with the Company or any subsidiary is terminated for a reason other
than those described in the preceding sentence the unvested portion of the
Option shall terminate immediately and the entire portion of the Option which
was vested prior to termination of Employee's employment, to the extent that it
was exercisable for sixty (60) days following Employee's termination date. To
the extent that the Option was not exercisable on the Employee's termination
date, or if the Option is not exercised (to the extent it was entitled to be
exercised), within the 60 day period, the Option shall terminate.

         (c)      BREACH OF NON-DISCLOSURE COVENANT NOT TO COMPETE.
Notwithstanding anything provided to the contrary in the Plan, if Optionee
breaches any applicable nondisclosure covenant or covenant not to compete set
forth in any employment agreement between Optionee and the Company or a
Subsidiary, or otherwise applicable to Optionee under the law of the
jurisdiction where Optionee is employed, then all unexercised Options, whether
vested or unvested, shall immediately terminate.

         7.       NON-TRANSFERABILITY OF OPTIONS. The Option may not be sold,
pledged, assigned, hypothecated, transferred, or disposed of in any manner
other than by will or by the laws of descent or distribution and may be
exercised, during the lifetime of the Optionee, only by the Optionee.

         8.       CONDITIONS UPON ISSUANCE OF OPTION SHARES.

         (a)      Option Shares shall not be issued pursuant to the exercise of
an Option unless the exercise of such Option and the issuance and delivery of
such Option Shares


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pursuant thereto shall comply with all relevant provisions of law, including,
without limitation, the Securities Act of 1933, as amended, the Securities
Exchange Act of 1934, as amended, the rules and regulations promulgated
thereunder, and the requirements of any stock exchange upon which the Common
Stock may then be listed, and shall be further subject to the reasonable
approval of counsel for the Company with respect to such compliance.

         (b)      As a condition to the exercise of an Option, the Company may
require the person exercising such Option to represent and warrant at the time
of any such exercise that the Option Shares are being purchased only for
investment and without any present intention to sell or distribute such Option
Shares if, in the reasonable opinion of counsel for the Company, such a
representation is required by any of the aforementioned relevant provisions of
law.

         (c)      As a condition to the issuance of Option Shares, the Optionee
shall (a) remit to the Company at the time of any exercise of the Option any
taxes required to be withheld by the Company under federal, state or local laws
as a result of the exercise of the Option, and/or (b) instruct the Company to
withhold in accordance with applicable law from any compensation payable to the
Optionee the taxes required to be held by the Company under federal, state or
local laws result of the exercise of the Option. The determination of the
amount of any such withholding shall be made by the Company in its sole
discretion.

         (d)      All Option Shares issued pursuant to the exercise of the
Option shall be subject to the terms and provisions of the Stock Restriction
Agreement, an example of which is attached hereto as Exhibit B.

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the date first above written.

                                            OPTIONEE

                                            /S/ Karl Gemperli
                                            -----------------------------------

                                            NAME: KARL GEMPERLI

                                            AIRPORT SYSTEMS INTERNATIONAL,
                                            INC.

                                            a Kansas corporation

                                            BY: /S/ KEITH S. COWAN
                                                -------------------------------

                                                KEITH S. COWAN, PRESIDENT


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        EXHIBITS

A.       RESTATED 1991 STOCK OPTION PLAN

B.       STOCK TRANSFER RESTRICTION AGREEMENT