PHOTOS: US President's $223 mn 'doomsday plane'

The United States has built the most impressive aircraft in the world to keep the President, Secretary of Defence, Joint Chiefs of Staff and other key personnel in the air and out of danger from the ultimate worst-case scenarios.

The 'doomsday plane' was mobilised in the tumultuous hours after planes crashed into the World Trade Centre, the Pentagon and Pennsylvania on 9/11.

Built at a cost of $223 million, the plane can stay in the air for days without refueling and offer protection from all manner of threats, including nuclear attacks and meteor strikes from outer space.

about the 'doomsday plane'...

The E-4B, a militarised version of the Boeing 747-200, is a four-engine, swept-wing, long-range, high-altitude airplane capable of being refueled in flight.

Its larger size provides approximately triple the floor space of the earlier EC-135 command post.

The main deck is divided into six functional areas: a command work area, conference room, briefing room, an operations team work area, and communications and rest areas.

An E-4B crew may include up to 112 people, including a joint-service operations team, an ACC flight crew, a maintenance and security component, a communications team and selected augmentees. 

The E-4B has electromagnetic pulse protection, an electrical system designed to support advanced electronics and a wide variety of new communications equipment.

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.

An advanced satellite communications system improves worldwide communications among strategic and tactical satellite systems and the airborne operations centre. 

To provide direct support to the president, secretary of defense and the JCS, at least one E-4B is always on alert at one of many selected bases throughout the world. 

The modified 747s, codenamed E-4B, can travel at speeds up to 620 miles per hour, 40 miles per hour faster than their commercial counterparts.

"If the command centres that are on the ground in the United States have a failure of some sort, or attack, we immediately get airborne. We're on alert 24/7, 365," ABC News quoted Captain W Scott Ryder, Commander, NAOC, as saying.

Air Combat Command is the Air Force single-resource manager for the E-4B, and provides aircrew, maintenance, security and communications support. E-4B operations are directed by the JCS and executed through US. Strategic Command.

USSTRATCOM also provides personnel for the airborne operations centre.

"Constantly there's at least one alert airplane waiting to get airborne," he added.

Ryder also said that a highly-trained security team travels with the plane.

The men sleep nearby so the plane can launch within five minutes of an attack, he added.

The E-4B evolved from the E-4A, which had been in service since late 1974. The first B model was delivered to the Air Force in January 1980, and by 1985 all aircraft were converted to B models.

All E-4Bs are assigned to the 55th Wing, Offutt Air Force Base, Nebraska. 

In case of national emergency or destruction of ground command control centres, the aircraft provides a highly survivable, command, control and communications centre to direct US forces, execute emergency war orders and coordinate actions by civil authorities.

On June 7, Boeing was handed over the contract to upgrade the E-4Bs. The upgrade will allow the E-4Bs to operate more efficiently at airports and in crowded airspace. Their solution will be derived from current Boeing 737 cockpits, and the 4 E-4Bs will be upgraded in 3 phases.

Phase 1 includes next-generation flight-management hardware and software, as well as a multimode receiver radio that combines several aircraft systems into a single component.

The initial E-4B CNS/ATM Phase 1 aircraft is expected to enter flight test in Q4 2012.