Canadian airlines and flight crews are forbidden to consume cannabis for at least 28 days before going on duty, the country's transportation regulator said on Thursday.

Transport Canada's new policy, which is effective immediately, says no person should work while "under the influence of any drug," according to statement posted on its website.

Canada became the first developed country in the world to legalize cannabis in October 2018. Since then, various industries have issued guidelines around cannabis use.

The aviation regulator said the move aligns with scientific consensus on drug usage while on the job and the Department of National Defence and Royal Canadian Mounted Police's policies on cannabis.

Canada's military prohibits members of the armed forces from consuming cannabis eight hours before any duty, 24 hours before any operation of weapons or vehicles and 28 days before high altitude parachuting, operating in a hyperbaric environment and serving on a military aircraft.