Definition
A controller advisory informing the pilot that ATC is no longer providing radar services to the aircraft. After this point, the pilot is responsible for their own navigation, traffic separation, and terrain avoidance, except where other services (such as a tower or another controller) take over.
Plain English
ATC is telling you they are no longer watching you on radar or providing radar-based help. From now on, you are on your own for navigation and seeing other traffic, unless someone else picks you up.
Context Anchor
You may hear this from ATC when leaving radar coverage, leaving controlled radar service, or switching to a part of the flight where radar help is no longer being provided.
Derivation
Radar comes from “radio detection and ranging,” meaning finding objects and measuring their distance by radio signals. Terminated means ended. Together, the phrase means the radar-based service has ended, not that the flight itself has ended.
Why Pilots Care
The pilot must now resume full responsibility for navigation, traffic separation, and altitude without ATC radar support.
Intuition Check
Do not hear “terminated” and think your flight plan, clearance, or radio contact has automatically ended. Here, it only means the radar service has ended unless ATC says something more specific.
Example Sentence 1
Approach called, 'Cessna 23 Alpha, radar service terminated, squawk VFR, frequency change approved,' so I switched to the CTAF and started self-announcing.
Example Sentence 2
Leaving Class C airspace, ATC advised radar service terminated, squawk VFR, and resume own navigation.