query: When was the U.S. Air Force established?
passage: United States Air Force
The United States Air Force (USAF) is the aerial and space warfare service branch of the United States Armed Forces. It is one of the five branches of the United States Armed Forces, and one of the seven American uniformed services. Initially formed as a part of the United States Army on 1 August 1907, the USAF was established as a separate branch of the U.S. Armed Forces on 18 September 1947 with the passing of the National Security Act of 1947. It is the youngest branch of the U.S. Armed Forces, and the fourth in order of precedence. The USAF is the largest[13] and most technologically advanced[14] air force in the world. The Air Force articulates its core missions as air and space superiority, global integrated intelligence, surveillance, and reconnaissance, rapid global mobility, global strike, and command and control.
passage: The U.S. Air Force (song)
Following the initial change on June 20, 1941 of the American air force’s name from "Army Air Corps" to "Army Air Force(s)", to the post-World War II 1947 establishment of the separate "U.S. Air Force", an attempt was made to change the sixth line of each verse so that the last word rhymed with "force" instead of "corps". Thus, "Off with one helluva roar!" became "Off on one helluva course!"; "Gave us wings, ever to soar!" became "Gave our wings every resource!"; and "We'll be there, followed by more!" became "We'll be there, ever on course!"