National Emergency Airborne Command Post. That was the plane.
My old man was the Senior Project Officer for the purchase of the first two E-4s - one became Air Force One, the other NEACAP. Upon receipt of the aircraft, he became the Director of Operations. End shameless plug.
Somebody, be it the VP, SecState, SecDef, etc. was driven to Andrews and put on that plane. Wouldn’t you want to take a look before starting endless briefings and whatnot?