In 1986, a study carried out in the USA by Sears examined the significant causes of 93 aircraft accidents. The causes can be classified as follows:
- 33% of the accidents were caused by pilots who deviated from basic operational procedures.
- 26% were caused by inadequate cross-check by the second crew member.
- 13% were due to design faults, and in
- 12% of the cases, maintenance and inspection deficiencies were to blame for the accident.