In case of national emergency or destruction of ground command and control centers, the E-4B provides a highly survivable command, control and communications center to direct U.S. forces
Taken on Feb. 20, 2017 the interesting images in this post show a KC-135 Stratotanker assigned to the 100th Air Refueling Wing (ARW) prepares to refuel a U.S. Air Force (USAF) E-4B transporting the U.S. Secretary of Defense.
The E-4B serves as the National Airborne Operations Center (NAOC) and is a key component of the National Military Command System for the President of the United States (POTUS), the Secretary of Defense (SECDEF) and the Joint Chiefs of Staff (JCS). In case of national emergency or destruction of ground command and control centers, the aircraft provides a highly survivable command, control and communications center 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. Additionally, the E-4B provides outside the continental United States travel support for the SECDEF and his staff to ensure Title 10 command and control connectivity.
The E-4B, a militarized version of the Boeing 747-200, is a four-engine, swept-wing, long-range high-altitude airplane capable of refueling in flight. The main deck is divided into six functional areas: a command work area, conference room, briefing room, an operations team work area, communications area and rest area. 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 augmentees.
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 center. 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.

To provide direct support to the POTUS, the SECDEF, and the JCS, at least one E-4B NAOC is always on 24-hour alert, 7-days a week, with a global watch team at one of many selected bases throughout the world.
In addition to its national and nuclear command and control (NC2) mission, the E-4B provides support to the Federal Emergency Management Agency, which provides communications and command center capability to relief efforts following natural disasters, such as hurricanes and earthquakes.
Story by Staff Sgt. Micaiah Anthony, 100th Air Refueling Wing; Photo credit: Staff Sgt. Micaiah Anthony / U.S. Air Force
Artwork courtesy of AircraftProfilePrints.com