Since introduction in 1974-1975, the Boeing E-4 Advanced Airborne Command Post (AACP) has served the United States Air Force (USAF) service in the flying Command & Control (C2) role. The service took on four aircraft for its requirement and these were used to directly succeeded an aging fleet of EC-135J platforms in same role. The E-4 was developed atop the existing (and proven) framework of the Boeing Model 747-200 commercial airliner and is assigned to the 595th Command and Control Group out of Offutt Air Force Base, Nebraska under the banner of the 1st Airborne Command Control Squadron.
The fleet were born through a 1973 USAF initiative which originally called for two aircraft and these were designated as "E-4A" while being powered by 4 x Pratt & Whitney JT9D engines. By the end of 1975, a third aircraft was added to the group and this new entry was powered by 4 x General Electric GE F103 (CF6) engines instead. The "E-4B" variant was a "one-off" conversion aircraft with additional equipment (including a noticeable dorsal spine bulge) and this entry joined the fleet during December of 1979. In 1985, the original three aircraft were revised to the B-model operating standard and the CF6 engine was selected to power them all. A modernization of the entire fleet was had in 2005 during the post-9/11 period and the start of the global 'War on Terror'.
Externally the aircraft retains much of the form of the Boeing 747 airliner complete with its two-story front fuselage section, four-engined (underwing, nacelled) layout, and a single tail fin aft. A series of antenna protrude from the spine of the fuselage which gives away the many systems and sensors the aircraft carries. Internally, the aircraft is arranged as a series of compartments which are used to accomplish various tasks in the event of a national emergency. While the standard operating crew is four (including two pilots), the fuselage can situate up to 112 personnel and specialists to cover the critical functions of the USAF and government during a national emergency. The aircraft is fully-equipped with advanced systems as well as countermeasures and other protective means (including EMP resistance and nuclear shielding). Additionally, an in-flight refueling capability can be used to extend the range of the E-4 command post considerably over the previous EC-135J platforms they replaced.
At least one E-4 is held "on-call" at any given time by the USAF/U.S. government and regularly deploys with the President of the United States when overseas trips are had. When the President is aboard the E-4 himself, the aircraft uses the callsign of "Air Force One".
The Northrop Grumman E-10 MC2A, built upon the framework of the Boeing Model 767-400ER, was intended as the direct successor to the E-4 but the project was cancelled in 2007.
231.30 ft (70.5 m)
195.87 ft (59.7 m)
63.32 ft (19.3 m)
418,878 lb (190,000 kg)
826,403 lb (374,850 kg)
603 mph (970 kph; 524 kts)
45,932 feet (14,000 m; 8.7 miles)
7,140 miles (11,490 km; 6,204 nm)
E-4A - Initial Production Models; three examples produced; later brought to E-4B standard.
E-4B - Fitted with CF6-50E2 engines of 52,500lb thrust each; EMP protection; special shielding from thermal and nuclear sources; additional specialized equipment.