Definition
An unidentified radar return that appears on a radar display without a known physical aircraft, vehicle, or weather source to account for it. Angels are typically caused by flocks of birds, swarms of insects, atmospheric anomalies such as temperature inversions, or reflections from other small airborne objects.
Plain English
A blip on a radar screen that the operator cannot match to any real aircraft or known object. Something is reflecting the radar signal, but it is not what radar is meant to track.
Context Anchor
Seen or heard mainly in military, airshow, and informal aviation communications, not in standard civilian radio wording with air traffic control.
Derivation
Borrowed from informal radar operator slang dating to World War II. Operators used 'angel' as a light, almost humorous label for ghostly, unexplained returns that seemed to come from nowhere -- as if from the sky itself.
Why Pilots Care
Gives a fast, unambiguous way to pass altitude information during high-workload phases without saying long numbers.
Intuition Check
Angel does not mean a heavenly being here. In this aviation use, it is a slang way to say 1,000 feet of altitude.
Example Sentence 1
The controller noted several angels on the scope near the coast and attributed them to a large flock of migrating birds.
Example Sentence 2
Approach asked the flight for their angels before clearing them to descend.