Definitions of Key Terms Used by

The NTSB and the FAA use definitions for accidents and incidents that are described below. Note that there are several terms in the definition of an accident that also have specific meanings when used by the FAA and the NTSB. is focused for the most part on fatal events, a term that has a specific definition in this site but one that is not defined and used in the same way by the NTSB, FAA, or any other civil aviation regulatory body.

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.

Hull Loss
An aircraft damaged to the extent that it is not economically feasible to repair it. This would include aircraft that are destroyed or aircraft that are missing.

An occurrence, other than an accident, associated with the operation of an aircraft that affects or could affect the safety of operations.

Minor Damage
Aircraft damage that does not qualify as substantial.

Serious Injury
Injuries that result in one or more of the following conditions:

  • Requires hospitalization for more than 48 hours, commencing within seven days from the date the injury was received,
  • Results in a fracture of any bone (except simple fractures of fingers, toes, or nose),
  • Involves lacerations that cause severe hemorrhages, nerve, muscle, or tendon damage.
  • Involves injury to any internal organ, or
  • Involves second or third degree burns, or any burns affecting more than five percent of the body surface.

Substantial Damage
Damage or structural failure that negatively affects an aircraft's structural strength, performance, or flying characteristics, and which would require significant repair or replacement of the affected component or system. Substantial damage excludes damage to landing gear, wheels, tires, and flaps. It also excludes bent aerodynamic fairings, dents in the aircraft skin, small punctures in the aircraft skin, ground damage to propeller blades, or damage to only a single engine.

The following definitions are used by, and the NTSB, FAA, and other national and international aviation organizations may not have an equivalent definition.

Fatal Event
Any circumstance where one or more passengers die during the flight from causes that are directly related to a civilian airline flight. The fatal event may be due to an accident or due to a deliberate act by another passenger, a crew member, or by one or more persons not on the aircraft. These events include sabotage, hijacking, or military action and exclude cases where the only passenger deaths were to hijackers, saboteurs, or stowaways. Also excluded are situations where the only deaths are to crew members or to people outside of the aircraft.

Significant Event
In addition to the term fatal event, also uses the term signficant event. These are events involving either an aircraft or an aviation organization that is not a fatal event, but is noteworthy for other reasons. Significant events are not included in any of the risk statistics compiled by, but they are of interest to airline passengers and the aviation safety community for other reasons. Characteristics of significant events include, but are not limited to, the following:

  • The event receives signficant attention from the news media.
  • The event has either causes signficant changes to airline safety or security policy, or has the potential to lead to such changes.
  • The event is associated with one or more hazards that may lead to a fatal event.
  • It is a passenger fatality event that does not involve an aircraft type typically used in passenger service in North America, Japan, Australia, or the European Community.
  • It is an accident or deliberate act that results in the deaths of people who were not passengers on the aircraft.
  • The event involves a prominent political figure or celebrity.
  • The event is a non-fatal airliner accident that is the subject of a major accident investigation.

Whether an event is included as a significant event is based on many factors. Every event that has one or more of these characteristics may not be included. Also, significant events may be added to the site long after the event took place.

Numbered Events
On, numbered events are those events that are used to compute risk-related statistics. Numbered events exclude significant events, but include all fatal events and those events where there is substantial indirect evidence that one or more passengers may have been killed, but no direct evidence exists.

Examples of events with substantial indirect evidence of one or more passenger fatalities include an airliner that has gone missing for more that 30 days, or a passenger who may have gone missing after having been ejected from an aircraft during a decompression event.

An event where the flight crew intentionally lands an aircraft in some body of water such as a lake, a river, or the open ocean. In addition, the event would have to meet the following conditions or criteria:

  • The water landing has to be intentional. Accidental or unintentional landings or excursions onto water are excluded, such as runway overruns or controlled flight into water.
  • Uncontrolled impacts with water are excluded.
  • The body of water must be deep enough that if the aircraft sinks, some or all of the occupants would have to evacuate the aircraft cabin to avoid drowning.

Note:The FAA, NTSB, ICAO, and other national or international aviation organizations may have different definitions for ditching.

Definitions of Key Terms Used by -- Revised: 29 June 2014