Air Force One was the official plane for the President of the United States. It was used when making official trips around the world.
During the 2012 apocalypse, Air Force One was the plane that many U.S government officials (ironically, minus the President himself as he chooses to stay behind with his wife and his people but his daughter didn't stay behind) used to fly from Washington D.C. to China when the worldwide apocalypse happened. They fly, luckily avoiding the ash cloud that engulfed the United States just a few hours before it. Inside the airplane, many staffs of the U.S government collected updates information regarding to the apocalypse, recording every seismic activity and volcanic activity, which were earthquakes, volcanic eruptions and tsunamis that were destroying the Earth's continents and killing several humans globally.
It is later caught by a megatsunami when the Worldwide Flooding occurred. Just one minute left after the megatsunami struck the arks, it was destroyed when collided into Ark 4.