Pre-employment testing, as well as DOT-mandated periodic, random and incident-driven testing, if memory serves, thanks to the cannabis-smoking idiot who crashed a passenger train some years back.

"The Omnibus Transportation Employee Testing Act of 1991 requires drug and alcohol testing of safety-sensitive transportation employees in aviation, trucking, railroads, mass transit, pipelines and other transportation industries. DOT publishes rules on who must conduct drug and alcohol tests, how to conduct those tests and what procedures to use when testing. These regulations cover all transportation employers, safety-sensitive transportation employees and service agents -roughly 12.1 million people. Encompassed in 49 Code of Federal Regulations (CFR) Part 40, the Office of Drug & Alcohol Policy & Compliance (ODAPC) publishes, implements and provides authoritative interpretations of these rules."

AA, as a transportation employer, certainly fills the bill...