Hollis Hills grew up in Pasadena, California. He joined the Royal Canadian Air Force (R.C.A.F.) in June 1940 and became a pilot on June 22, 1941, with the R.C.A.F.’s 414 Squadron. Prior to Pearl Harbor, Hollis was transferred to Croydon (Greater London), England to continue to fly and train with the Royal Air Force. He was transferred to the U.S. Navy on November 8, 1942.