The United States Air Force became a separate military service on September 18, 1947, with the implementation of the National Security Act of 1947. The Act created the National Military Establishment, later renamed the United States Department of Defense, which was composed of three branches, the Army, Navy and a newly created Air Force. Prior to 1947, the responsibility for military aviation was divided between the Army (for land-based operations) and the Navy, for sea-based operations from aircraft carrier andamphibious aircraft. The Army created the first antecedent of the Air Force in 1907, which through a succession of changes of organization, titles, and missions advanced toward eventual separation 40 years later. The predecessor organizations leading up to today’s U.S. Air Force are:
- 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, U.S. Army (May 24, 1918 – July 2, 1926)
- U.S. Army Air Corps (July 2, 1926 – June 20, 1941)* and
- U.S. Army Air Forces (June 20, 1941 – September 17, 1947)**
* The Air Corps became a subordinate element of the Army Air Forces on 20 June 1941, and was abolished as an administrative organization on 9 March 1942. It continued to exist as a branch of the Army (similar to the infantry, quartermaster, or artillery) until reorganization provisions of the National Security Act of 1947 (61 Stat. 495), July 26, 1947.
**The Army Air Forces were abolished by Transfer Order 1, Office of the Secretary of Defense, September 26, 1947, implementing the same provisions. Transfer Order 1 was the first of 200 Army-Air Force transfer agreements drawn up in June and July, 1947, and ordered the transfer of all military and civilian personnel of the Army Air Forces to the Department of the Air Force and the USAF. The final transfer order was signed June 22, 1949.