Also found in: Financial.
The number of accidents in a given period of time against benchmarked hours flown/takeoffs completed/passenger-miles or kilometers/stage flights. In military aviation, the term refers to the number of accidents per 100,000 flying hours. Some air forces use 10,000 h as the benchmark. In commercial aviation, this refers to the number of accidents per 100 million passenger-miles or kilometers or per 100,000 stage flights. In general aviation, it is the number of accidents per 100,000 takeoffs. The reckoning period is generally a financial year or a calendar year and, in some cases, it is a five-year moving average. Accident rates are further subclassified as human error by the aircrew, ground crew error, and material failure, in addition to write-offs (damaged beyond economical repairs) and fatal accidents.