Air Force One is the call handle for any plane carrying the president but there is a designated and designed plane specific for the president in the Boeing VC-25which is the military version of the 747. When maintenance is done on this plane it has a sister plane that takes over duty. When the president is not onboard they are referred to by their tail numbers 28000 and 29000 instead of Air Force One. The VC-25A planes used as Air Force One are the most well-equipped and well-defended aircraft flying. Ready for business (with 85 phone lines) or wartime (they really can withstand a nuclear blast on the ground), today's Air Force One planes have 4,000 square feet of space for up to 76 passengers and a crew of 26. They each boast two galleys, with stocked fridges; a medical department; a supply of blood; and a well-stocked pharmacy. For the president, each plane is equipped with a private suite that has a small gym, bathroom, shower and sleeping quarters. Each has a flying Oval Office and its own situation room. Their defenses include electronic countermeasures, radar jamming and flares to confuse enemy missiles. They are also protected against electromagnetic pulses. The planes even have their own side exit doors, so they don't have to rely on airport stair vehicles.