CANCUN, Mexico (Reuters) - A deadly attack in London and debate over travel restrictions in the United States put safety concerns high on the agenda as global airline executives gathered on Sunday for the industry’s largest meeting of the year.

FILE PHOTO: A general view of Terminal 3 at Heathrow Airport near London, Britain October 11, 2016. REUTERS/Stefan Wermuth/File Photo

Alexandre de Juniac, director general of the International Air Transport Association (IATA), said the weekend’s violence in London could discourage potential visitors as similar attacks did in Europe last year.

“In previous events, in Brussels or in Paris, the traffic has reduced coming from certain regions of the world,” de Juniac said in an interview. “So it’s possible that there is an impact, but it’s a bit early to know how big this impact will be.”

Three attackers rammed a hired van into pedestrians on London Bridge and stabbed others nearby on Saturday night, killing at least seven people, in Britain’s third major militant attack in recent months.

U.S. President Donald Trump seized on the violence to argue for an executive order that would temporarily ban entry into the United States of people from six predominantly Muslim countries. The ban has been blocked in the courts and Trump’s legal team has asked the Supreme Court to reinstate it.

“We need the Travel Ban as an extra level of safety!” Trump said in a series of Twitter messages.

Airlines were quick to offer assurances and refunds to travelers on edge after the London attack, but it was unclear whether the impact on tourism would match the fallout from similar attacks in Europe last year.

Malaysia Airlines has offered free refunds to customers flying into London through June 5 and may extend that offer, Chief Executive Peter Bellew told Reuters.

“Very few people have taken up the offer and we haven’t seen any drop-off in bookings to London. But it’s not good,” he said.

Last year, carriers in Europe reported a drop in demand from travelers from Asia after attacks in Paris, Brussels and Nice, but air traffic has recovered this year.

Bellew said carriers in Asia could rethink growth plans for new routes to Europe or the United States.

“I think it will have an impact,” Bellew said, adding that it built on Asian airlines’ aversion to political risk in Europe and the United States.

“For colleagues in Asia, there’s no risk sending a new plane or new flight to China, or a new route from Australia. You will see a certain insularity in this vast region.”