Passengers onboard an Air Canada domestic flight between Toronto Pearson International Airport (YYZ) and Vancouver International Airport (YVR) were panicked when the aircraft had to divert to the U.S., knowing that they had marijuana in their possession.

In what should have been an uneventful five-hour journey, Air Canada flight AC125 from Toronto to Vancouver had to divert to Seattle–Tacoma International Airport (SEA) due to dense fog in British Columbia.

Having attempted two landings, the crew aboard the Boeing 787 Dreamliner decided that their best course of action was to divert the plane to a fog-free Seattle, refuel and then try to land in Vancouver when the fog had cleared.

After the aircraft landed it developed mechanical problems

What the 255 passengers hadn’t counted on was that once the plane touched down on American soil, it went out of service due to maintenance. When flying domestically in Canada you do not need a passport, have any customs control, and can carry a certain amount of marijuana or cannabis-related products.

Recreational marijuana was made legal in Canada just over a year ago, so those who like to partake in using marijuana have no problem carrying weed on their person. While this might be OK in Canada, it’s not so popular with law enforcement in the United States and has quite severe consequences for anyone caught bringing a controlled substance into the country.

The possession of marijuana is still a federal offense in some parts of the U.S.A.

A U.S.-based immigration lawyer Les Saunders told Canadian website Global News that flying with marijuana might not be such a smart move.

“It’s playing with fire,” he said. “Canadians have to be careful when they’re on flights back and forth across Canada. I wouldn’t carry any of that stuff if I was a Canadian traveling by airplane.”

Saunders talked about the consequences should U.S. customs agents of the TSA find marijuana in your possession.

Despite several states in America legalizing marijuana, in the State of Washington where the aircraft was diverted to the possession of the drug is still illegal under federal law and carries heavy penalties.

Saunders says he sees it all the time when unsuspecting Canadian drive their cars into the United States while having marijuana in the glove box. In cases where it is obvious that the amount of marijuana found is for personal use, people are given what they call a “zero-tolerance fine “of $500.

You also face the chance of the U.S. customs agent putting you on a list of people banned from entering the United States for life.

In Canada, it is currently legal to carry 30 grams of cannabis but it is illegal to take it outside of country. In the end, none of the passengers had to undergo searches and managed to get on a later flight to Vancouver none the worse for their ordeal.

You might want to think twice about flying with marijuana in Canada

When asked about the diversion to Seattle Air Canada sent an email to Canadian online media outlet Narcity which said:

“Due to fog at YVR as well as at the surrounding BC-area airports Seattle was the closest airport that wasn’t affected by the fog and was able to take a plane of that size.

“After landing, the aircraft subsequently developed an unexpected mechanical fault requiring a maintenance inspection.

“Air Canada is handled by a partner company in Seattle, and special, exceptional arrangements were immediately made for the US authorities to enable all customers to clear customs without the usual documentation.”

The lesson here is that if you are flying domestically in Canada and have marijuana in your possession, if you're told the plane is being diverted to the U.S.A. you might want to queue up for the lavatory.