The world’s largest plane makers were the biggest and earliest beneficiaries of the Obama administration’s detente with Iran. President Donald Trump’s decision to walk away from the deal could leave them the first and hardest hit.

Boeing Co. , the world’s largest plane maker, and European rival Airbus SE signed more than $40 billion in combined plane deals with Iranian carriers after the U.S. and five other world powers lifted sanctions in return for Tehran agreeing to curb its nuclear ambitions.

Those orders stand to be voided after the White House said it would rescind licenses for plane exports to Iran, following President Trump’s decision Tuesday to pull the U.S. out of what he called a “one sided” nuclear deal.

The fortunes of Boeing and Airbus are closely linked to far bigger markets in the U.S., Europe and Asia, but Iran has long presented an attractive growth market, because of the country’s old fleet of planes and large population eager to travel. Iranian officials have suggested the country could need 400 planes or more over the next decade, making it potentially one of the world’s biggest airplane growth markets.

Iranian airlines that were stuck with some of the world’s oldest fleets after years of being blocked from buying new planes were looking to introduce new western jets to revive their fortunes.