The AWACS aircraft: a 707 with a thirty-foot radar disc on its back. Live E-3 Sentry positions.
No E-3 Sentry is transmitting ADS-B at the moment.
Military aircraft are not obliged to broadcast, so this happens regularly. The count refreshes every thirty seconds.
Nothing of this type is up right now.
The E-3 is the aircraft that made AWACS a household word. The rotating disc above the fuselage houses a radar that can see several hundred kilometres in every direction, and the twenty-odd people inside use it to run the air battle — telling fighters where to go rather than going there themselves.
NATO operates its own fleet from Geilenkirchen in Germany, registered in Luxembourg with LX-N serials, and those aircraft are among the most reliably visible military aircraft over Europe. They fly long racetrack orbits, often over Poland, Romania or the Baltic, for many hours at a time.
The airframe underneath is a Boeing 707, so the fleet is very old. NATO plans to replace it with the E-7 Wedgetail from around 2031; the US Air Force is retiring its own E-3Gs faster than replacements arrive.
Airborne Warning and Control System. In practice it means a flying radar station that detects aircraft at long range and directs friendly fighters, well beyond what ground radar can see.
Geilenkirchen in western Germany. The fleet is jointly owned by NATO members and registered in Luxembourg, which is why the aircraft carry LX-N serials rather than any single nation's.
The Boeing E-7 Wedgetail. NATO has committed to it for around 2031, and the United Kingdom and Australia already operate it. American plans have been repeatedly revised.