The E-4B Nightwatch — nicknamed the 'Doomsday Plane' — is one of four highly modified Boeing 747-200s operated by the U.S. Air Force as the National Airborne Operations Center. At least one is on continuous ground alert at all times.
Its job is simple and terrifying: if nuclear war breaks out and ground command centers are destroyed, the E-4B becomes the mobile command post from which the President, Secretary of Defense, or designated successor can direct U.S. military forces and coordinate a response. It can stay airborne for over a week with aerial refueling. It is hardened against electromagnetic pulse. It carries equipment to communicate simultaneously with submarines running silent under the ocean, ground forces, satellites, and allied nations. Whatever happens to everything below it, the E-4B keeps the chain of command intact.
The aircraft is known by the Cold War nickname NEACP — National Emergency Airborne Command Post, pronounced 'kneecap' — and its callsign was historically GORDO. Weather observers at Offutt Air Force Base in Nebraska, where these aircraft are based, used to mark their wind recorder traces with 'GORDO' and the time whenever one landed, because a 747 touching down made everything in the old control tower tremble.
So what was one doing at a public airshow in Sacramento, California? Honestly — your guess is as good as mine. But I had a camera.