More Pilots in Crashes Are on Drugs, Report Says

More pilots involved in airplane crashes are testing positive for drugs, according to an analysis of toxicology reports going back 20 years by the National Transportation Safety Board.

According to the draft report released Tuesday, in 1990 just 9.6% of pilots involved in crashes tested positive for one drug, compared to 39% in 2012. Drug mixing—which can be an especially dangerous and unpredictable way to consume drugs—has been on the rise as well.

The study crunched the numbers on toxicology reports from nearly 6,700 pilots who were killed in airplane crashes between 1990 and 2012. The study looked at the use of both legal and illegal drugs and found increases in the use of all drugs.

Alcohol was not considered in the study.

The most commonly used drug that can cause impairment was diphenhydramine, a sedative antihistamine used in cold medicine and other related applications. Few pilots tested positive for illegal drugs, the report says, but the percentage of pilots who tested positive for marijuana increased over the study period, mostly in the last 10 years.

Because the vast majority of airplane crashes involve non-commercial flights, more than 90% of the pilots tested were private pilots rather than commercial air carrier pilots.