Like the Air Force, the Air National Guard has its roots in the U.S. Army. Military flying missions have their genesis in the Army Signal Corps. This included military balloon operations and later the first military heavier-than-air powered flights.
The Air Force became a separate branch of military service via the National Security Act of 1947. It wasn’t long before the existing National Guard Army Air Force units began operations under the command of the newly minted United States Air Force.
The official birth date of the Air National Guard as a reserve component of the Air Force is September 18, 1947.