In aviation accidents, a chain of events (or error chain) is the many contributing factors typically lead to an accident, rather than one single event. These contributing actions typically stem from human factor-related mistakes and pilot error, rather than mechanical failure. A study conducted by Boeing found that 55% of airline accidents between 1959 and 2005 were caused by such human related factors, while only 17% of accidents were caused by mechanical issues with the aircraft.
The Tenerife airport disaster, the worst accident in aviation history, is a prime example of an accident in which a chain of events and errors can be identified leading up to the crash. Pilot error, communications problems, fog, and airfield congestion (due to a bomb threat and explosion at another airport) all contributed to this catastrophe.