I don't think this aircraft, former callsign "NIGHTWATCH-01" is used much any more. In its place, is a group of US Navy TACAMO E-6B Aircraft, which are basical

I don't think this aircraft, former callsign "NIGHTWATCH-01" is used much any more. In its place, is a group of US Navy TACAMO E-6B Aircraft, which are basically converted Boeing 707's outfitted with sophisticated communications equipment. There are usually 3 to 4 of these E-6 Mercury's in the air at any given point during the day. https://en.wikipedia.org/wiki/Boeing_E-6_Mercury https://en.wikipedia.org/wiki/Boeing_E-6_Mercury The reason why the US Navy operates them is they host a huge long-wire antenna that unspools out of the tail of the aircraft and is used to communicate VLF (very low frequency) transmissions to submarines. It is super slow speed data - usually along the lines of "surface for more info" type messages. But since they provide that critical communications link to submarines, from an airborne capacity, they've been pressed into service to function as an overall airborne command post. Their primary communications capabilities are: 1) VLF as mentioned above, using a long wire spool out the tail to send short messages to submarines. 2) Satellite - to maintain general worldwide coverage 3) UHF Orderwire - which is a nationwide air to ground digital/analog orderwire network - basically a huge digital data and voice conference line. The ground based GEP (Ground Entry Points) are interconnected via AT&T hardened communications links and hosted on AT&T microwave towers all across the country. 4) UHF Air to Ground capabilities to send command and control messages to US missile silos 5) HF Radio communications capabilities as a backup to satellite and orderwire.