Accident. (ICAO Annex 13)
a) a person is fatally or seriously injured as a result of
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:
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)
Hijack.
Other occurrence.
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:
- 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,
- adversely affects the structural strength, performance or flight characteristics of the aircraft, and
- would normally require major repair or replacement of the affected component,
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).
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.