A jetliner arrives at London's Heathrow Airport earlier this year. On Wednesday, the U.K.'s highest court reversed a ban on the airport's controversial plans for a third runway.

A jetliner arrives at London's Heathrow Airport earlier this year. On Wednesday, the U.K.'s highest court reversed a ban on the airport's controversial plans for a third runway. / AFP via Getty Images

Just half a year after climate activists won a big legal victory in the U.K. effectively blocking plans for a third runway at London's Heathrow Airport on environmental grounds, the country's highest court has turned the tables once more.

The British Supreme Court on Wednesday overturned the appellate court decision, reopening the door to a significant — and controversial — expansion of one of the world's busiest international hubs.

Previously, in the appellate court decision in February, judges found that the U.K. government had failed to mind the country's international climate commitments when developing plans for the third runway in its Airports National Policy Statement, or ANPS. The British government did not appeal that decision, but the company that operates the airport did.

And on Wednesday, a panel of five justices unanimously agreed with Heathrow Airport Holdings, saying that — unlike the appellate court — they were satisfied with the considerations undertaken by government officials.

"This is not a case in which the Secretary of State omitted to give any consideration to the Paris Agreement; nor is it one in which no weight was given to the Paris Agreement when the Secretary of State decided to issue the ANPS," the court found, referring to the 2015 Paris climate deal in which nearly 200 countries pledged to reduce their greenhouse emissions.

"On the contrary, the Secretary of State took the Paris Agreement into account and ... he gave weight to it and ensured that those obligations would be brought into account in decisions to be taken under the framework established by the ANPS."

The ruling represents a stinging reversal for climate activists, who had celebrated the February decision as a "hugely influential" landmark. Plan B, the climate-centric legal charity that helped bring the original legal challenge to the runway, protested that Wednesday's ruling "has betrayed us all."

"The pandemic has reminded us of our subjection to natural laws," Plan B Director Tim Crosland said in a statement, which he posted one day before the official release of the ruling, breaking a news embargo in order to protest its "deep immorality." "The Paris Temperature Limit is all that divides us from a grim future of crisis upon crisis."

A demonstrator raises a sign protesting plans for a third runway in London, the same day that the British Supreme Court reopened the door to the runway. The runway had previously been blocked on environmental grounds.

A demonstrator raises a sign protesting plans for a third runway in London, the same day that the British Supreme Court reopened the door to the runway. The runway had previously been blocked on environmental grounds. / AFP via Getty Images

Meanwhile on Wednesday, the company behind Heathrow lauded the judgment as "the right result for the country."

"Only by expanding the UK's hub airport can we connect all of Britain to all of the growing markets of the world, helping to create hundreds of thousands of jobs in every nation and region of our country," a Heathrow spokesperson said in a statement.

"Heathrow has already committed to net zero," the spokesperson added, "and this ruling recognises the robust planning process that will require us to prove expansion is compliant with the UK's climate change obligations, including the Paris Climate Agreement, before construction can begin."

Now, the judgment does not ensure that a third runway will, in fact, be built.

The coronavirus pandemic has sent the aviation industry reeling, severely diminishing passenger demand and potentially setting Heathrow's expansion plans back by at least five years. Climate activists have also vowed to continue to challenge the plans in court at every step of the proposed development — and their cause has got the support of one prominent local politician.

"This decision to allow Heathrow Airport a third runway will have a damaging impact on air quality, noise and London's ability to achieve net-zero carbon by 2030," Sadiq Khan, mayor of the British capital, said in the wake of the Supreme Court ruling. "I urge Heathrow to drop these damaging plans and work with us on a cleaner, greener recovery."

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Tags: U.K.  air travel  London  climate change