http://en.wikipedia.org/wiki/Aviatio..._and_incidents
An accident survey of 1,843 aircraft accidents from 1950 through 2006 determined the causes to be as follows:
* 53%: Pilot error
* 21%: Mechanical failure
* 11%: Weather
* 8%: Other human error (air traffic controller error, improper loading of aircraft, improper maintenance, fuel contamination, language miscommunication etc.)
* 6%: Sabotage (bombs, hijackings, shoot-downs)
* 1%: Other cause