When is the us air force birthday?

September 18, 1947

The U.S. Air Force was created by the National Security Act of 1947 and was signed into law by President Harry. S. Truman. Born out of the Army Air Corps, it became a full partner with the U.S. Army and U.S. Navy in defending the country. General Carl A. Spaatz served as the first Air Force Chief of Staff.