Plain English Meaning
The aircraft is officially cleared to fly because it matches its approved design, is in safe working condition, and all required paperwork and inspections are up to date.
Full Definition
The condition of an aircraft being legally and mechanically fit for flight, meaning it conforms to its FAA-approved type design and is in a condition for safe operation, with all required inspections, airworthiness directives, and maintenance actions completed and properly documented.
Context Anchor
Encountered during preflight assessment, before the pilot accepts or operates the aircraft.
Derivation
From 'air' plus 'worthy,' meaning deserving or fit. 'Worthy' comes from Old English 'weorth,' meaning of value or merit. So '' literally means 'fit for the air' — the aircraft has earned the to fly.