Boeing E-4

The Boeing E-4 Advanced Airborne Command Post (AACP), the current "Nightwatch" aircraft, is a series of strategic command and controlmilitary aircraft operated by the United States Air Force (USAF). The E-4 series are specially modified from the Boeing 747-200B for the National Emergency Airborne Command Post (NEACP) program. One of its primary purposes is continuity of government during nuclear warfare, thus being nicknamed the "Doomsday plane".

The E-4 serves as a survivable mobile command post for the National Command Authority, namely the president of the United States, the secretary of defense, and successors. The four E-4s are operated by the 1st Airborne Command and Control Squadron of the 595th Command and Control Group located at Offutt Air Force Base, near Omaha, Nebraska. An E-4 when in action is denoted a "National Airborne Operations Center" (NAOC).

The E-4B aircraft are to be replaced by the SNC E-4C Survivable Airborne Operations Center.