Still, with the arrival of the first donor 747 aircraft looking imminent, SNC is already taking important steps forward in crafting the successor to the E-4B Nightwatch 'doomsday plane.' ...

The E-4B is a modified Boeing 747-200B, just like the VC-25A. A significant number of avionics systems are common to the VC-25A and E-4B. Another position of note is the flying crew chief.