The FAA recently amended Part 121 regulations governing drug and alcohol testing to clarify that “each person who performs a safety-sensitive function for a regulated employer by contract, including by subcontract at any tier, is subject to testing.” Guidance has been conflicting for more than a decade about which contractors were subject to drug and alcohol testing. These amendments, which the agency said supercede all previous guidance on the subject of testing contractors, become effective on April 10.