According to the White House, "Air Force One" is the official air traffic control call sign for (any) US Air Force aircraft carrying the President of the United States, while Air Force Two is the call sign for US Air Force aircraft carrying the Vice-president of the United States. Strictly speaking, this call sign refers to the US Air Force aircraft carrying out a particular mission, not permanently to the aircraft themselves. That said, "Air Force One" is now associated with the presidential VC-25 aircraft and "Air Force Two" with the C-32A aircraft.