Time magazine has a short profile of the National Airborne Operations Center, aka the "Doomsday Plane." If there's a nuclear attack, one of four tricked-out Boeing 747 would serve as the Pentagon's mobile office. Apparently, defense secretary Robert Gates and his staff occasionally commute to meetings on it.
From Time:
…The NAOC can refuel in midair and is designed and supplied with engine oil, and food and water for the crew to be able to stay aloft for days. Its full crew includes intelligence analysts, communications specialists, maintenance troops, and even its own security force. It constantly monitors all major U.S. commands and the location of nuclear forces, keeps an eye on potentially hostile military troops, gathers intelligence data, and monitors the whereabouts of every U.S. government official in the line of succession. The NAOC also carries with it at all times about a dozen of the most relevant war plans in case senior officers need them at hand.
Link to Time article, Link to more info and photos at the Federation of American Scientists
