Definition
A signed certification by an authorized person stating that maintenance, preventive maintenance, a rebuild, or an alteration has been performed on an aircraft or component in accordance with the applicable regulations and approved data, and that the work performed makes the aircraft or component airworthy and approved for return to service.
Plain English
A written, signed statement from a qualified mechanic or repair station saying the work on the aircraft has been done correctly and the aircraft is safe and legal to fly again.
Context Anchor
Seen in aircraft maintenance records, logbooks, work orders, and after inspections or repairs before the aircraft is flown again.
Derivation
From 'maintenance' (the work performed to keep the aircraft airworthy) and 'release' (in the legal sense of releasing something back into service or use). The word 'release' here carries the meaning of formally letting the aircraft return to flight after it has been held out of service for the work.
Why Pilots Care
A pilot must verify a valid maintenance release before flight to confirm the aircraft is legally airworthy and safe.
Intuition Check
Do not read release as just giving the aircraft back to the owner. Here, release means a formal signed approval that the maintenance was completed properly and the aircraft or part may return to service.
Example Sentence 1
After the 100-hour inspection was complete, the mechanic signed the maintenance release in the logbook so the aircraft could return to the flight line.
Example Sentence 2
Before the ferry flight the pilot checked the maintenance release to confirm the engine work was approved.