President Donald Trump on Thursday said all Canadian-built aircraft would lose their US certification until Canada approves American-made Gulfstream business jets, a stunning move threatening major travel disruptions if enacted. “We are hereby decertifying their Bombardier Global Expresses, and all Aircraft made in Canada, until such time as Gulfstream, a Great American Company, is fully certified, as it should have been many years ago,” Trump wrote. He additionally threatened a 50 per cent tariff on all Canadian aircraft sold to the United States. It was not immediately clear through what process Trump could unilaterally decertify aircraft or what that decertification would entail. While the Global Express is a business jet, Trump’s threat to decertify “all” Canadian aircraft would also appear to include CRJ regional jets and Airbus A220s — used by several major US airlines for shorter-range flights.