skippedonce has it correct
Aeronautical Division, Signal Corps August 1, 1907 – July 18, 1914
Aviation Section, Signal Corps July 18, 1914 – May 20, 1918
Division of Military Aeronautics May 20, 1918 – May 24, 1918
Air Service, United States Army May 24, 1918 – July 2, 1926
United States Army Air Corps July 2, 1926 – June 20, 1941
United States Army Air Forces June 20, 1941 – September 18, 1947
United States Air Force September 18, 1947–present