Members of the Canadian aviation industry are forbidden from consuming cannabis for at least 28 days before going on duty, according to new rules now in force.

Canadian Aviation Regulations require that pilots, cabin crew, and air traffic controllers must have a certain level of "fitness for duty" on the job, Transport Canada said Thursday. That means they cannot use or be "under the influence of any drug that impairs the person's faculties to the extent that aviation safety is affected," the agency said.

As such, four weeks is the minimum time required to be free of cannabis before being allowed to work, the aviation regulator said. But the new rules don't preclude airlines or airports from requiring even stricter requirements of their employees.

After the government legalized recreational use of cannabis last fall, Transport Canada undertook a review of its policies with regards to impairment.

The new rules in keeping with what Department of National Defence and the Royal Canadian Mounted Police have come up with for their workers, and "aligned with the best available science," the agency said.

The rules are in place "effective immediately," Transport Canada added.