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Donald Trump’s broadside against Canadian aircraft has rattled investors and unsettled a group of people not accustomed to attracting the US president’s ire: wealthy American private jet owners.

The US president lashed out at Ottawa on Thursday evening claiming it had “refused” to certify a new fleet of American Gulfstream planes and said he would be “hereby decertifying” Canadian Bombardier Global Express jets and “all aircraft made in Canada”.

Tariffs of 50 per cent would be imposed on all aircraft sold into the US from Canada unless the situation was “immediately corrected”, he added.

Trump’s message triggered a roughly 7 per cent decline in Bombardier’s share price on Friday and it has yet to recover to its previous level.

But the threatened levies have baffled people in aviation circles, with private jet sellers and owners trying to understand the implications of the president’s social media post for their multimillion-dollar transactions.

“If they were able to decertify — my God! It would have a big impact on corporate aviation in the US,” said Steve Versano, chief executive of The Jet Business, a private jet showroom in London.

A US official on Friday clarified Trump’s position would only apply to new aircraft and Washington would “not be decertifying existing planes in operation”.

But it was unclear which planes beyond Bombardier’s Global Express models would fall under Trump’s threat, nor how he planned to decertify the aircraft. The US aviation regulator, the Federal Aviation Administration, is responsible for certification.

The Bombardier Global Express is typically used as a business jet by wealthy individuals, and retails at close to $80mn for the newest model, according to aviation website Bolt Flight, although actual prices usually vary depending on customer customisation requests.

But Paul Jebely, an aviation lawyer representing what he describes as “a large cadre of folks in the 0.0004 per cent club”, said even the idea that the US regulator might withdraw a plane’s right to fly dented jet values.

“It means that [private jet owners’] aircraft, at this moment, are worth a lot less than they were before the tweet or the Truth Social post came out,” he said.

Under global aviation rules, the country where an aircraft is designed is responsible for issuing its primary certification. The regulators in other countries typically follow the lead of the primary regulator but there can be a lag.

Trump said Canada had refused to certify the Gulfstream 500, 600, 700 and 800 aircraft. Gulfstream received US certification for the G500 and G600 in 2018 and 2019. Neither has been certified in Canada but both have received the nod from the European Union Aviation Safety Agency (EASA). The FAA and EASA last April certified the Gulfstream G800 jet.

The Canadian regulator, Transport Canada, has not confirmed Trump’s claim. It said: “Canada is working with the US Federal Aviation Administration, Bombardier and General Dynamics to resolve outstanding certification matters in a way that protects safety and regulatory integrity, while maintaining market access on both sides of the border.”

The impact of Trump’s statement on some of America’s wealthiest people underscores the unpredictable consequences of the president’s sudden trade salvos on US allies and partners.

His social media attack against Canada’s aviation regulator came against the backdrop of a broader deterioration in relations between Ottawa and Washington. Canadian Prime Minister Mark Carney two weeks ago suggested in a widely publicised speech at Davos that the US was rupturing the world order.

It is unclear whether Trump will follow through on his social media post and take action that would legally block certifications for Canadian planes.

But Jebely said the uncertainty was having a chilling effect on transactions.

“I have a very hard time imagining that was intentional or well thought out, but it has a very chilling effect because it is the first time we’re seeing this level of over-reach,” he said. “We’re talking about the constitutionally protected rights of private jet owners. But it’s got a much wider implication.”

Versano also said the uncertainty “is the problem for us, for people in the industry”. He added one transaction he was brokering involving the sale of a Bombardier jet into the US had been put on hold following Trump’s post.

“We’ve been working on it for the last two weeks, three weeks, but they’ve said ‘hey, you know, we have to hold off right now. Let’s see what happens here’.”

Bombardier said the company had “taken note” of Trump’s post and was in contact with the Canadian government. “Our aircraft, facilities and technicians are fully certified to FAA standards and renowned around the world,” it said.

It added: “Thousands of private and civilian jets built in Canada fly in the US every day. We hope this is quickly resolved to avoid a significant impact to air traffic and the flying public.”

General Dynamics, which owns Gulfstream, declined to comment. The US company earlier this week reported strong demand for its Gulfstream aircraft.

The White House did not respond to a request for comment.