Last updated: 9 December 2004
Definitions are consistent with those of the International Civil Aviation Organization (ICAO), NTSB and Boeing.

Accident. (ICAO Annex 13)
An occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight until such time as all such persons have disembarked, in which:

a) a person is fatally or seriously injured as a result of
- being in the aircraft, or
- direct contact with any part of the aircraft, including parts which have become detached from the aircraft, or
- direct exposure to jet blast,

except when the injuries are from natural causes, self inflicted or inflicted by other persons, or when the injuries are to stowaways hiding outside the areas normally available to the passengers and crew: or

b) the aircraft sustains damage or structural failure which:
- adversely affects the structural strength, performance or flight characteristics of the aircraft, and
- would normally require major repair or replacement of the affected component,

except for engine failure or damage. when the damage is limited to the engine, its cowlings or accessories: or for damage limited to propellers, wing tips, antennas, tires, brakes, fairings, small dents or puncture holes in the aircraft skin: or

c) the aircraft is missing or is completely inaccessible.

Incident. (ICAO Annex 13)
An occurrence, other than an accident, associated with the operation of an aircraft which affects or could affect the safety of operation.

Hijack means the unlawful seizure or wrongful exercise or control of the aircraft (or the crew thereof).

Other occurrence.
Safety occurrences that can not be defined as 'accident', or 'incident'. Usually these cases involve aircraft being damaged (beyond repair) on the ground as a result of hurricanes, typhoons, sabotage, hangar fires etc.

Unfiled occurrence.
Insufficient information is available to determine if the exact type of occurrence.

Hull loss / write-off (Aviation Safety Network).
Airplane damage that is beyond economic repair. Hull loss / write-off also include events in which: