Having spent two years at Purdue University, Thompson was called up into the United States Army Air Corps in 1943, a week after he had married his childhood sweetheart, Carolyn Kramer. Thompson served as a P-47 instructor at Moore Field in Mission, Texas until January 1945, when he earned an assignment to the Army's first helicopter class at Chanute Field, Illinois. Later, he was assigned to the Bridgeport, Connecticut, plant of Igor Sikorsky, who pioneered helicopters in America.