Boeing E-4

The Boeing E-4, nicknamed “Doomsday plane,” a militarised Boeing 747-200, is an American wide-body, four-engine Advanced Airborne Command Post (AACP). It serves as an aerial command centre for the President, the Secretary of Defense, and the Joint Chiefs of Staff in case of national emergency or destruction of ground facilities. It also supports the Secretary of Defense and his staff when travelling outside the continental United States.

The E-4A, the first variant, had the same systems as the EC-135 it replaced, but with more space and longer loiter time, entered service in 1974. The E-4B began service in 1980; it had protection against electromagnetic pulse, nuclear and thermal shielding, advanced electronics, and communications equipment. By 1985 all three E-4As had been upgraded to -B standard by 1985.

Airframe construction is mainly of aluminium alloy. The fuselage is a semi-monocoque structure with an upper deck, forward of the wing containing the cockpit and passenger space. The low mounted wings and conventional tail unit are of cantilever design with sweep back. The retractable undercarriage is a tricycle type. The flight crew of four consists of two pilots, a navigator, and a flight engineer. The main deck is divided into six work areas, seating up to 112 people.

Powered by four General Electric F103 (CF6) high-bypass turbofan engines, pod mounted two under each wing giving the E-4b a cruise speed of 895 km/h (556 mph), a maximum speed of 895 km/h (602 mph), a 14,00 m (45,000 ft) service ceiling. With in-flight aerial refuelling, it can remain airborne for a full week, only limited by the consumption of engine lubricants.