Armstrong learned to fly under the Civilian Pilot Training program in 1941. In 1943 he joined the Army Corps, and trained as co-pilot on B-17 bombers. On his fifth mission over Germany, his plane was badly damaged by anti-aircraft fire, seriously injuring the pilot. Armstrong was able to land the plane, and received the Distinguished Flying Cross for Heroism. He later opened a fixed-base operation at the Scott City, Kansas, airport, and became a Federal Aviation Administration pilot examiner, giving more than 1,000 flight tests during his career. As sales manager for a local Cessna distributor, he established dealerships throughout Kansas and Oklahoma. In 1960, he established “Skycraft”, a fixed base operation in Hutchinson, Kansas. He flew every day between June 1, 1965 and January 15, 1969, an achievement which was recognized in the 1984 Guinness Book of Aircraft Facts and Feats.