Plain English Meaning
The qualified people who work on the aircraft itself — checking it, fixing it, and signing it off as safe to fly.
Full Definition
The certificated mechanics, technicians, and inspectors responsible for inspecting, servicing, repairing, and approving an aircraft for return to service in accordance with FAA regulations and the manufacturer's maintenance instructions.
Context Anchor
A pilot may involve maintenance personnel when a problem is found during preflight, after an abnormal indication in flight, or when deciding whether an aircraft issue needs correction before the next flight.
Derivation
Maintenance comes from an older word meaning “to keep or preserve.” Personnel means “staff or people assigned to a job.” Together, the phrase points to the people whose job is to keep the aircraft in safe working .