Trump has threatened to revoke certification of Bombardier planes and impose new tariffs if Canada does not certify aircraft from U.S. rivals.

Shares in Canadian aircraft maker Bombardier plummeted after U.S. President Donald Trump threatened to revoke certification of the private jet maker’s large-cabin jets “and all Canadian-made aircraft” and impose a 50 per cent import tariff on new planes until Canada certifies the latest aircraft produced by U.S. rival Gulfstream.

Shares of the plane maker fell 9% on Friday morning after Trump issued the threat late Thursday.

While a White House official told Reuters that Trump was not recommending decertification of Canadian-made aircraft currently in operation, the president’s warning late Thursday caused confusion and alarm among airlines and aviation analysts, as well as private jet buyers and owners.

“If for any reason this situation is not corrected immediately, I will impose a 50% tariff on all aircraft sold to the United States by Canada,” Trump said in a post on Truth Social.

Amanda Applegate, an attorney at Soar Aviation Law who is an expert in U.S. business aviation law, said on Friday that the post prompted inquiries from clients who own or want to buy Bombardier aircraft.

Wider tensions also emerged between the neighbors after Canadian Prime Minister Mark Carney last week urged countries to embrace it, citing U.S. trade policy. The end of the rules-based global order Washington once embraced.

Aircraft and aerospace parts have been largely unscathed by Trump’s U.S.-led trade war, with Canadian-made aircraft continuing to be exported south of the border under the U.S.-Mexico-Canada trade agreement.

Trump also said he would “decertify the Bombardier Global Express and all Canadian-made aircraft” until the Gulfstream aircraft is certified. Gulfstream is part of General Dynamics.

The threat, if carried out, would have a huge impact on U.S. airlines such as American Airlines and Delta Air Lines, which rely on Canadian-made aircraft for many of their regional services. The United States is also the world’s largest business aviation market.

Data provider Cirium said there are 150 Global Express aircraft currently registered in the United States, operated by 115 operators, and a total of 5,425 Canadian-made aircraft of all types, including narrow-body jets, regional jets and helicopters, currently registered in the United States.

Bombardier said in a statement Thursday that it was “aware” of Trump’s posts and was contacting the Canadian government. The company employs more than 3,000 people at nine major U.S. facilities and creates thousands of U.S. jobs through 2,800 suppliers, it added.

“Thousands of Canadian-made private and commercial aircraft fly in the United States every day. We hope this issue can be resolved quickly to avoid significant impact to air traffic and the flying public,” the company said.