Construction, which was challenged by Friends of the Earth, London Mayor Sadiq Khan and other groups after the U.K. government approved the plan, can go ahead, after judges on Wednesday threw out a series of lawsuits that sought to thwart the expansion.

Opponents alleged the proposal violated the U.K.’s climate change policy and didn’t take account of the Paris climate accord. But that agreement isn’t part of U.K. law, even though the country has ratified it—and this posed an “overarching difficulty” to the lawsuit, the three judges said.

“We understand that these claims involve underlying issues upon which the parties—and indeed many members of the public—hold strong and sincere views,” the judges said in the unanimous ruling.

“There was a tendency for the substance of the parties’ positions to take more of a center stage than perhaps it should have done, in a hearing that was only concerned with the legality, and not the merits” of the government policy statement that approved expansion, they said.

Heathrow is “delighted,” a spokesman said. “The debate on Heathrow expansion has been had and won, not only in Parliament, but in the courts also.”

Shares in International Consolidated Airlines Group SA, owner of British Airways, Heathrow’s biggest carrier, rose as much as 1.3% in the wake of the ruling.

Virgin Atlantic, which operates most of its flights from Heathrow, said it will target a greater percentage of takeoff and landing slots.

“Without the third runway, Virgin Atlantic cannot realize its ambition to become the U.K.’s second flag carrier,” the airline said.

Plan B, one of the groups that challenged the expansion, expects to appeal the ruling, it said in a statement.

“This is a disappointing judgment by the court, but it is increasingly difficult to see how the government’s reckless plans to expand Heathrow Airport can proceed,” its director Tim Crosland said.

After decades of delays tied to concerns about extra aircraft noise, increased pollution, the demolition of homes and the impact on roads, construction of the runway could begin as soon as 2021, officials said last year. The new landing strip is expected to open in 2026, lifting annual capacity to 135 million travelers from 2018’s 80.1 million.

The runway was approved by Parliament in June as part of a national policy statement, helping to minimize further procedural logjams, with planning authorities confined to considering elements of the proposal rather than whether it should be built at all.

The airport operator has spent years struggling to win permission to build the new runway, which has constrained its ability to increase flights. In 2018, it was only able to boost flight numbers 0.2% because of a shortage of slots.