On Sept. 18, 1947, the Department of the Air Force was created under the National Security Act of 1947. Prior to gaining its independence, military aviation in the U.S. existed as a component of the U.S. Army, tracing its early roots back to the Aeronautical Division of the U.S. Army Signal Corps, which was formed on August 1, 1907. The mission of the United States Air Force is to fly, fight, and win … airpower anytime, anywhere.