Doomsday planes hover as Trump tests positive for COVID-19
Like the E-3 Sentry, the E-6B Mercury is based on the Boeing's 707-320 airliner. Its purpose is to carry out the “Take Charge And Move Out” (TACAMO) mission, which means ensuring the communication relay between on one side the Pentagon, the White House, the U.S. Navy bases, and on the other side the Ohio submarines in charge of carrying out the first nuclear strikes with their submarine-launched ballistic missiles (SLBM), in the event of a thermonuclear conflict outbreak. Submarines are part of the United States' nuclear-deterrent triad, along with strategic bombers and intercontinental ballistic missiles.
With such a role, the Boeing E-6B Mercury is designed to survive the electromagnetic pulse of a nuclear explosion. Its communication system includes a double encrypted communications system Very Low Frequency and Very Very Low Frequency (VLF/VVLF) system that allows talking with immersed submarines within a radius of 150 to 200 kilometers (95 to 125 miles).
The timing of the flights, however, was "purely coincidental", according to the U.S. military.