President Trump on Thursday threatened to "decertify" Canadian-made aircraft and slap a 50% tariff on planes sold into the United States, in a potential move that would mark an unprecedented intervention in aviation regulation, given this function is traditionally handled by the Federal Aviation Administration (however, the FAA has yet to issue comment).

In a Truth Social post, Trump linked the threat to Canada's refusal to certify several Gulfstream business jet models, amid broader growing tensions related to him calling the country America's "51st state". 

"We are hereby decertifying their Bombardier Global Expresses, and all Aircraft made in Canada," Trump wrote on Truth Social, warning that if the dispute is not "immediately corrected," Washington would impose a "50% Tariff on any and all Aircraft sold into the United States of America."

But again, the reality remains that no US president has ever directly "decertified" commercial aircraft, but it signifies a further breakdown in Washington-Ottawa relations. The full Trump statement is below:

The same day that Trump made the threat, Prime Minister Mark Carney called for the US to respect Canadian sovereignty, following widespread reports that Alberta separatists had met Trump administration on multiple occasions over the last nine months.

The group, Alberta Prosperity Project (APP), does have a significant following and number of members. They are asking Washington to provide political and monetary support for an "independent" Alberta.

Carney hit back, saying he expects "the US administration to respect Canadian sovereignty - I'm always clear with President Trump to that effect".

At the same time, Alberta Premier Danielle Smith said she expected American officials to allow discussions about the province's "democratic process" to remain internal, among Albertans and Canadians. The US shouldn't meddle, she's made clear.

But US Treasury Secretary Scott Bessent recently signaled at Davos: "Alberta is a natural partner for the US. People are talking. People want sovereignty. They want what the US has got."