It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
originally posted by: Zaphod58
a reply to: NNN87
They're tracked by transponder. The aircraft sends a unique identifier, along with altitude, airspeed, and other information. You're not looking at a radar picture. It's normally sent by a dedicated radio signal, but newer types also use satellites, if the aircraft is equipped.