After graduating from Harvard University in 1940, Illman joined the United States Army Air Force where he was a B-25 aircraft instrument instructor. He worked for Trans World Airlines (TWA), for 30 years, was self-employed as a management consultant, and helped establish a national airline in Saudi Arabia. Illman authored The Pilot’s Radio Communications Handbook, The Pilot’s Handbook of Aeronautical Knowledge, and The Pilot’s Air Traffic Control Handbook. He received Member of the Year Award and the Founder’s Award from the Kansas Pilot’s Aviation, and accumulated 3,600 accident free flight hours in his Cherokee Piper aircraft. Illman was a dedicated aviation enthusiast and offered many hours of volunteer assistance to pilots and organizations around the state of Kansas.