Air Force One - technically whatever plane the President is on board but currently a Boeing 747-200 (and eventually a new 747-8) - costs over $200,000 an hour to operate. Speaking of 'operate' there's an onboard operating room staffed by a doctor whenever the plane is in flight.
There's 4000 square feet of interior space. The President has an office, there's a 'situation room' and a staff quarters spread out over three stories. There are actually two planes that each serve as Air Force One so that one can always be ready to fly.
I only recently learned how Air Force One got its name. (HT: Kalbozey)
The name was adopted in 1953, after a commercial plane, Eastern Air Lines Flight 8610, entered President Eisenhower's airspace when he was on board his plane, which had a similar name - Air Force 8610. After the incident, the term "Air Force One" was coined to avoid any confusion about which aircraft is carrying the commander-in-chief.
Up until 1962, though, the President flew in a commercially-produced plane. The first jet customized for Presidential use was a Boeing 707 which debuted in 1962. First Lady Jackie Kennedy "commissioned designer Raymond Loewy to create a new interior..and she oversaw the redesign of the blue exterior that still makes Air Force One so recognizable today."
Air Force One is a serious fighting fortress.
In 2016 Snopes had to debunk a story claiming that Cuban refugees had stowed away on board the President's plane seeking refuge in the U.S. It was insane, but people believed it.