The Heathrow Airport authorities won a Supreme Court challenge to start construction of its third runway, reported AFP.
The decision will bring cheer to the aviation industry, which has been decimated by the coronavirus pandemic as international travel effectively ground to a halt.
A bench of five judges at the UK's highest court ruled Wednesday that the UK had properly considered its commitments under the Paris Agreement, meaning its support for another runway at Europe’s busiest hub was legal. The judges overturned a lower court ruling, which forced the government to review its airport policy in light of environmental legislation.
Environmental group Greenpeace said Prime Minister Boris Johnson should still not allow the project to proceed, in the light of his government's targets on cutting carbon emissions.
The Supreme Court said the previous Conservative government had "no obligation" to consider the Paris climate agreement when it gave the nod to the extra runway.
"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," Heathrow said in a statement.
But Greenpeace UK urged the government to scrap the project.
The airport authorities added that it had "already committed" to net zero carbon emissions and that the latest ruling "recognises the robust planning process that will require... expansion is compliant with the UK's climate change obligations, including the Paris Climate Agreement."
Construction will now have to go through the planning process, and will face new challenges on the grounds of environmental impact.
Heathrow has said any new runway at the airport is unlikely to happen before 2030, if at all, dependent on post-COVID demand.
Opponents immediately branded the decision a "disaster" in terms of tackling climate change.