Missing plane mystery: Pilot suicide a taboo topic in past crash probes

The study found that during the 10 years ending in 2012, just eight of 2,758 fatal aviation accidents in the U.S. were caused by pilot suicide, a rate of 0.3 percent.

The report found that all eight suicides were men, with four of them testing positive for alcohol and two for antidepressants.

The cases ranged from a pilot celebrating his 21st birthday who realized a woman didn't want a relationship with him, to a 69-year-old pilot with a history of drinking and threatening suicide by plane.

Seven of the cases involved the death of only the pilot; in the eighth case, a passenger also died.

“Aircraft-assisted suicides are tragic, intentional events that are hard to predict and difficult to prevent,” the FAA's report found, adding that such suicides “are most likely under-reported and under-recognized.”

In at least one case, a major international airline allowed a pilot who had expressed suicidal thoughts to continue flying.

He flew nearly three more years, without incident, before he resigned in 1982 with severe obsessive-compulsive disorder, anxiety and depression.

The Sydney Morning Herald newspaper reported that the Workers Compensation Commission heard that the Qantas pilot struggled several times to resist an overwhelming urge to switch off the plane's engines.

Once during a flight to Singapore, the pilot's hand moved “involuntarily” toward the start levers and he was forced to “immobilize his left arm in order not to act on the compulsion.”