The suspected fentanyl-related overdoses of a Spirit Airlines pilot and his wife in their Dayton, Ohio-area home raise a frightening prospect: Has the opioid crisis that is destroying whole families entered the ranks of pilots entrusted with hundreds of lives each day?

Investigators have offered no indication that Brian Halye used drugs while piloting aircraft during his nine years with Spirit Airlines, but a Dayton Daily News examination has uncovered a system in which commercial pilots can go years without being tested for drugs.

Federal Aviation Administration’s guidance to airlines acknowledges the random drug test system established by U.S. code makes it “not uncommon for some employees to be selected several times, while other employees may never be chosen.” Moreover, pilots are not required to be drug tested during annual physical exams.

Of the pilots tested from 2010-2015, 165 were found to be using one or more drugs, according to the FAA.

Drug use among pilots is an enduring concern at the National Transportation Safety Board, the federal agency created by Congress to investigate transportation accidents and issue recommendations to improve safety.

In a 2014 study of fatally injured pilots from all forms of civil aviation, the NTSB said patterns of increasing drug use among pilots “are consistent with observed trends of increasing drug use by the U.S. population in general.”

At the time, the most common illicit drug detected in pilots involved in fatal plane crashes was marijuana, which was found in less than 4 percent of all pilots tested between 2008 and 2012, and was not found in any of the airline pilots tested.

But if Halye died from an accidental overdose of fentanyl, as the Montgomery County Coroner’s office suspects, another concern may have unfolded. With heroin and fentanyl invading the ranks of so much of the general population, is it too much to conclude that it is also present among those flying aircraft?

Halye and wife Courtney Halye were found by their four children in the bedroom of their Centerville home March 16. The coroner’s office is waiting on toxicology reports but has said the deaths appear to be fentanyl-related. Centerville police also say the drug use appears to be voluntary and consistent with an accidental overdose.

Spirit Airlines, a Florida-based “ultra-low fare” carrier, told the Dayton Daily News that it is “cooperating with any and all agencies investigating this case.”

A spokesman for the carrier would not say when, if ever, the airline tested Halye during his time as a pilot.

The FAA declined to acknowledge whether it is investigating Spirit Airlines following Halye’s death. The agency confirmed it has inspected Spirit Airlines’ drug and alcohol testing program before, but would not say how recently.