First Lieutenant Milhaupt was the pilot in a F-82 Twin Mustang night fighter with the 68th Fighter Interceptor Squadron, 6160th Air Base Wing. On March 14, 1951, while on a combat mission, he failed to return. He was listed as Missing in Action and was presumed dead on December 31, 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.