 Already prior to his enlistment in the Air Corps, he had been an avid amateur pilot, with a private pilot certificate and a commercial pilot license as well as over 400 hours of flying time.A highly proficient pilot, he entered a cross-country race with Leland Hayward in 1937, and was one of the early investors in Thunderbird Field, a pilot-training school built and operated by Southwest Airways in Glendale, Arizona.Stewart was also active in philanthropy over the years.