Definition
The procedure of starting an aircraft engine while in flight, typically following an in-flight shutdown or flameout, using either the airflow through the engine (windmilling) or the aircraft's starter system to restore engine operation.
Plain English
Restarting an engine while the airplane is already flying, after it has stopped running in the air.
Context Anchor
Seen in engine failure, engine restart, and emergency checklist discussions.
Derivation
A straightforward pairing of 'air' (in flight) and 'start' (begin running). The phrase distinguishes it from a 'ground start,' which is the normal startup before takeoff.
Why Pilots Care
Enables safe recovery and continued flight after an engine failure instead of requiring an immediate off-field landing.
Intuition Check
Air start does not mean starting an engine with compressed air on the ground. In this context, air means airborne: the engine is being restarted during flight.
Example Sentence 1
After the engine quit at cruise, the pilot established best glide speed and ran the air start checklist.
Example Sentence 2
The emergency checklist directed an air start attempt before declaring an engine failure.