Aircraft on Ground

(AOG)

AOG is a term in aviation maintenance indicating that a problem is serious enough to prevent an aircraft from flying.

Airworthiness

Airworthiness defines whether an aircraft is capable of safe flight. When registered, an airworthy aircraft receives a certificate of airworthiness from its national registration authority. This certificate remains valid if specified maintenance procedures are followed. It is illegal to fly an aircraft without an airworthiness certificate.