U.S. 'Doomsday Plane' spotted over California

America's version of the 'Doomsday' aircraft is preparing for action as the so-called 'Nightwatch' was spotted circling the skies of Southern California.

Test pilots and personnel from the 418th Flight Test Squadron, out of Edwards Air Force Base, California, conducted aerial refuelling testing with a KC-46 Pegasus and an E-4B Nightwatch, out of Offutt Air Force Base, Nebraska on 4 April.

The E-4B Nightwatch, an airborne command centre for the U.S. President in times of war, can be used as a flying command centre.

The aircraft serves as the National Airborne Operations Center and is a key component of the National Military Command System for the President, the Secretary of Defense and the Joint Chiefs of Staff.

In case of national emergency or destruction of ground command and control centres, the aircraft provides a highly survivable command, control and communications centre to direct U.S. forces, execute emergency war orders and coordinate actions by civil authorities. The conduct of E-4B operations encompasses all phases of the threat spectrum.

An E-4B may include seating for up to 112 people, including a joint-service operations team, Air Force flight crew, maintenance and security component, communications team and selected officials.

The E-4B is protected against the effects of electromagnetic pulse and has an electrical system designed to support advanced electronics and a wide variety of communications equipment. An advanced satellite communications system provides worldwide communication for senior leaders through the airborne operations centre. Other improvements include nuclear and thermal effects shielding, acoustic control, an improved technical control facility and an upgraded air-conditioning system for cooling electrical components.