The U.S. National Transportation Safety Board definition of an aviation accident is as follows:

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 and all such persons have disembarked, and in which any person suffers death or serious injury, or in which the aircraft receives substantial damage.
An aviation incident is an occurrence other than an accident, associated with the operation of an aircraft, which affects or could affect the safety of operations.

Other countries adopt a similar approach, although there are minor variations, such as to the extent of aviation-related operations on the ground, covered, as well as with respect to the thresholds beyond which an injury is considered serious or the damage is considered substantial.

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