The worst case scenario. The E-4B is designed as a last resort for US military leadership to use to control a nuclear war if all land based systems have been destroyed. (http://www.military.cz/wallpaper/page1/e4b.jpg)
One of the most technologically advanced weapons in the United States' war chest is the E-4B National Airborne Operations Center (NOAC). This aircraft has many common nicknames including "the doomsday plane", "TCAMO" (Take Charge And Move Out), the "Nightwatch", and "NEACP" (pronounced "Knee Cap" for National Emergency Airborne Command Post). This plane has many myths associated with it but its primary purpose is to provide a safe and livable platform for the President, Secretary of Defense and Chairman of the Joint Chiefs to use as a mobile command post.

Early in the Cold War the US military leadership determined the United States' policy of not launching a first strike nuclear attack would place the US at a great disadvantage in the event of an attack by a hostile country. In the event of a Soviet first strike many, if not all, ground based command centers would be destroyed. It was to prevent this from happening and to insure the survival of the US command capabilities that the E-4A (the predecessor to the E-4B) was created. The E-4B is based on a modified Boeing 747-200 airframe and is designed to support 114 people at full battle ready.

 An E-4B landing (http://www.ndu.edu/nwc)

It is built on three decks.The first being primarily storage, support systems, machine rooms, and crew quarters. The middle deck containing a command work area, conference room, briefing room, operations room work area, communications area, and rest quarters. This plane is made to survive an electromagnetic pulse (EMP), has state-of-the-art direct fire countermeasures, and is capable of being airborne for more than a week. One E-4B is always on alert and as of August 1994 the E-4B is also responsible for communications for FEMA in times of extreme national crisis.

 Jag