The National Security Act of 1947 became law on 26 July 1947. The lawmakers stated their intentions in a Declaration of Policy at the beginning of the act: To provide a comprehensive program for the future security of the United States; to provide three military departments: the Army, the Navy, and the Air Force; to provide for their coordination and unified direction under civilian control and to provide for the effective strategic direction and operation of the armed forces under unified control. To coordinate national security matters, the act established the National Security Council (NSC), the Central Intelligence Agency under the NSC, and the National Security Resources Board.
The law created the civilian positions of Secretary of Defense and Secretary of the Air Force, to be filled by presidential appointment. The functions assigned to the Commanding General, Army Air Forces, were to be transferred to the Department of the Air Force. The act provided for the orderly transfer of these functions as well as the property, personnel, and records over a two-year period.
The United States Air Force was established within the Department of the Air Force. The Army Air Forces (and the Army Air Corps and the Air Force Combat Command) would be transferred to the Air Force, and the agencies themselves would cease to exist. Under the Secretary of the Air Force, the Chief of Staff, was to exercise command over the new service.
General Carl A. Spaatz became the first Chief of Staff of the Air Force on 26 September 1947. When General Spaatz assumed his new position, the first Secretary of the Air Force, W. Stuart Symington, was already on the job, having been sworn in on 18 September 1947. He had been Assistant Secretary of War for Air and had already worked closely with General Spaatz. The new Air Force was fortunate to have these two men as its first leaders. They regarded air power as an instrument of national policy and of great importance to national defense. Both men also knew how to promote air power and win public support for the Air Force.
See the AFHSO publication by Herman S. Wolk: Planning and Organizing the Post War Air Force, 1943-1947.