LONDON (Reuters) - A vote by British lawmakers to approve a third runway at Heathrow closes the political discussion on the issue after decades of uncertainty, the airport’s chief executive said on Tuesday, even as it faces legal challenges.

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Heathrow posted a record 38.1 million passengers in the first half of the year on Tuesday and has long sought expansion as it is capacity constrained at peak times.

Last month, British lawmakers voted strongly in favor of building a new runway at Heathrow, Europe’s biggest airport, paving the way for the airport’s expansion some 70 years after the last full-length runway was built in the London area.

But a junior minister resigned over the plan and London Mayor Sadiq Khan said he would bring legal action to block the expansion.

Asked whether the parliamentary vote was only a first step, and further hurdles could follow, Heathrow’s chief executive John Holland-Kaye said: “No, I think this is it.”

“There’s now an overwhelming consensus in parliament ... I think the politics is now through,” he told Reuters, adding that he was unconcerned by legal challenges.

“You expect to have judicial review challenges with any big infrastructure project ... The challenge doesn’t stop the planning process, so we’re getting on with confidence.”

Environmentalists have voiced concerns about air quality in London and the impact on climate change. Heathrow, which is also a major trading hub, has also come under pressure to keep the costs of expansion down.

Heathrow, owned by Ferrovial, the Qatar Investment Authority, China Investment Corporation and others, has said construction could start in 2021, with the runway open in 2026.

Britain is due to leave the European Union in March next year, and there is the possibility that flights would be affected if no Brexit deal is agreed.

Holland-Kaye said that the airport had extended its bond maturity for two years to make its finances more resilient to any uncertainty, but he was confident that planes would keep on flying.

He said that the prospects for a deal had been improved after British Prime Minister Theresa May reached agreement at her Chequers country house with senior ministers on how Britain should approach Brexit

“The is a bit more realism on the European side on just what they have to lose,” he said.

“I was encouraged by the Chequers deal. There is a pragmatism on both sides. This is not easy ... but there will be opportunities coming out of Brexit.”