Accident As defined by the NTSB, this is an occurrence associated with the operation of an aircraft where as a result of the operation of an aircraft, any person (either inside or outside the aircraft) receives fatal or serious injury or any aircraft receives substantial damage. The occurrence is also not caused by the deliberate action of one or more persons and that leads to damage or injury. The NTSB definition, which is also used by the FAA, divides accidents into four categories: (1) Major - an accident in which a 14 CFR 121 aircraft was destroyed, there were multiple fatalities, or there was one fatality and a 14 CFR 121 aircraft was substantially damaged. (2) Serious - an accident in which there was either one fatality without substantial damage to a 14 CFR 121 aircraft, or there was at least one serious injury and a 14 CFR121 aircraft was substantially damaged. (3) Injury - a nonfatal accident with at least one serious injury and without substantial damage to a 14 CFR 121 aircraft. (4) Damage - an accident in which no person was killed or seriously injured, but in which any aircraft was substantially damaged