The NTSB today adopted a study of the prevalence of drug use among pilots involved in fatal plane crashes, the majority of which were general aviation accidents. The study found an upward trend in the use of over-the-counter and prescription medications and illegal drugs, all of which could impair pilot performance. In a statement by Acting Chairman Christopher Hart, "the key take-away from this study for every pilot is to think twice about the medications you're taking and how they might affect your flying. Many over-the-counter and prescription drugs have the potential to impair performance, so pilots must be vigilant to ensure that their abilities are in no way compromised before taking to the skies."

The study was based on toxicological tests done of more than 6,000 pilots who died in plane crashes between 1990 and 2012. The purpose of the study was to determine the prevalence of legal and illegal drugs in the systems of these fatally injured pilots. It did not attempt to determine whether drug use caused pilot impairment or contributed to the aircraft accident. According to the abstract of the study published by the NTSB today - the full report will be made publicly available in the next few weeks - "study results showed increasing trends in pilots’ use of all drugs, potentially impairing drugs, drugs used to treat potentially impairing conditions, drugs designated as controlled substances, and illicit drugs. The most common potentially impairing drug pilots had used was diphenhydramine, a sedating antihistamine and an active ingredient in many OTC allergy formulations, cold medicines, and sleep aids. Although evidence of illicit drug use was found only in a small number of cases, the percentage of pilots testing positive for marijuana use increased during the study period, mostly in the last 10 years. " None of the airline pilots who died in fatal accidents were found to have used illegal drugs, although some had used medications that the study believed could be potentially impairing.

Of particular interest to current debates about doing away with medical certificates for additional general aviation pilots is the finding that pilots without medical certificates or with expired certificates were more likely to have used drugs, both legal and illegal, that could result in impairment. However, no conclusions were reached with regard to whether pilots without medical certificates had a higher accident rate, in part because the FAA does not maintain records on the number of pilots without medical certificates. The study was characterized as a first step in understanding drug use and accident risk.

The study reached conclusions and made recommendations to the Federal Aviation Administration and the fifty states. It also issued an alert to pilots "to consult medical professionals about the potentially impairing effects of any drug that they are taking, carefully read medication dosing instructions, and to refrain from flying if they feel impaired in any way."