They’re not. The Air National Guard became the reserve component of the United States Air Force on Sept. 18, 1947, when the Air Force broke from the U.S. Army to become a separate military service. Before 1947, the National Guard aviation units were part of the U.S. Army Air Forces. Some National Guard units trace their lineage to before World War I. The original 29 National Guard aviation units were formally reorganized and activated in 1921 to become part of the U.S. Army Air Corps and, later, the U.S. Army Air Forces, which served in World War II with great distinction. When the Air Force was created in September 1947 as a separate service, there were 59 aviation units in the National Guard, to include the original 29 observation squadrons mobilized in 1940. These units were all transferred from the Army Air Forces to the new Air Force, effective April 27, 1948.