On his return from Panama, Brett reverted to his permanent rank of lieutenant colonel. He was briefly stationed in Menlo Park, California, before moving to Langley, Virginia, where he became chief of staff to his old friend Frank Andrews, now the commander of GHQ Air Force. In February 1939 Brett moved to Wright Field as assistant to the chief of the United States Army Air Corps, also serving as commandant of the Air Corps Engineering School and the chief of the Materiel Division. Once again he held the rank of brigadier general before being promoted to major general on 1 October 1940.