Exhibit 16.1 April 10, 2002 Office of the Chief Accountant Securities and Exchange Commission 450 Fifth Street, N.W. Washington, D.C. 20549 Dear Sir/Madam: We have read the first two paragraphs of Item 4 included in Form 8-K dated April 3, 2002 of Innovative Solutions and Support, Inc. to be filed with the Securities and Exchange Commission on April 10, 2002 and are in agreement with the statements contained therein. Very truly yours, /s/ Arthur Andersen LLP cc: James J. Reilly Chief Financial Officer Innovative Solutions and Support, Inc.