Air Force One is the air traffic control callsign for any United States Air Force aircraft with the President of the United States on board.
Air Force One was attacked somewhere over California by Starscream, who gassed the President and its entire crew before taking it to the Grand Canyon. Starscream recorded a ransom message on the black box for Optimus Prime and left it somewhere where the humans would find it. Unfortunately it turned out that after listening to the message, the Autobots had other ideas, and rescued both the President and her plane. The crew came around to confusion over how they had ended up at the bottom of the Grand Canyon.