The “Doomsday” fleet came to be known as its current incarnation beginning in 1973, when the E-4 Boeing Model took over the mission of the proceeding EC-135. The fleet, which is comprised of four specially outfitted 747-200Bs, is the strategic command and military aircraft operated by the United States Air Force. The mission that the E-series took over was to serve as a mobile, survivable command post in the case of a national emergency, which may include destruction of ground or control operations related to US forces, and whose strategic actions will be dictated by the National Command Authority, specifically the Commander-in-Chief, Secretary of Defense, and Joint Chiefs of Staff. These command functions can extend to nuclear capability.
The original three E-4AS from 1973 were eventually upgraded and replaced, the first of the E-4Bs delivered in 1979, and the last of the four in 1985. The first three E-4As originally came to be as designated for everyday commercial craft, but after the last of the sale to an airliner fell through, Boeing offered the frames to the United States Air Force, which lead to a larger purchase of another craft, though Boeing wasn’t awarded the contract to outfit the planes with the specialized equipment. This new model housed all the same equipment as the EC-135, but was able to remain in flight for much longer, and fly faster.
Eventually, a fourth craft, an E-4B (designated such by an updated radome on the dorsal surface to house the super high frequency satellite antennae) was added to the fleet. The first three were then retrofitted, bringing the fleet of them to their current status as E-4Bs.
The Boeing 747-200 made a perfect complement to embrace the National Airborne Operations Center due to its enormous body and airframe, which can seat up to 112 people at any time. Those 112 include both crew and mission members, encapsulated in its 231’ length.
Besides capability for refueling in-flight, the E-4B is insulated or “hardened” against the effects of an Electro-Magnetic Pulse (EMP), and has advanced electronics and avionics used to sustain its communications equipment. Per the USAF’s official website, other features touted include an “advanced satellite communications system [which] produces worldwide communication for senior leaders through the [NOAC]. Other improvements include nuclear and thermal effects shielding, acoustic control, and improved technical control facility and an upgraded air conditioning systems for cooling electrical components”. In a nod to the good, old-fashioned way of doing things, these crafts are outfitted with analog flight instruments, as the older technology is less susceptible to EMP interference.
To provide its highest measure of support, every hour of every day, at least one E-4B is kept on high alert, through a global watch team primed with sharp eyes toward the horizon from a number of designated bases throughout the world. Without vigilance and keeping ahead of potential disaster, the effectiveness of the mission is jeopardized.
The secondary missions of the E-4B include VIP travel and FEMA support, which provides communications and command center capability to relief efforts following natural disasters.
In 2014, Boeing received a $9.8 million dollar contract to design and develop a modernized low-frequency transmit system, also known as the ‘kilometer band’, which is part of a larger $92 million effort to update the vessels. This should replace the obsolete technology in place, and is considered exceptionally useful for long range transmission, as it’s signal can be bounced off of the Earth’s ionosphere, or communicate with submarines (in a limited capacity) which are relatively close to the ocean’s surface.
The goal of the contract is to integrate multiple contacts into a single one, overseen by a single entity. And, ultimately to increase readiness of the fleet, which translates to readiness of the our nation.