The Court of Appeal ruled the government’s national aviation planning statement – which gives its blessing to Heathrow’s third runway – is void because it breaches the Paris climate agreement to limit global warming to 1.5C.
The Court ruled in favour of London Mayor Sadiq Khan, Hillingdon Council and environmental groups including Greenpeace.
Judges said the report “was not produced as the law requires”, adding “The Paris Agreement ought to have been taken into account by the Secretary of State”. It added: “That, in our view, is legally fatal.”
Prime minister Boris Johnson, whose Uxbridge constituency is near the airport, has previously pledged to lie down in front of bulldozers to block the scheme.
He has pointed out that the airport has not met its obligations on air quality and noise pollution and some believe a Court ruling against the airport will give Johnson a convenient get-out.
Plans to expand Heathrow were approved by MPs in 2018 with Johnson missing the vote by taking a trip abroad.
The government has not immediately sought permission to appeal, but a Heathrow spokesperson said it would appeal to the Supreme Court: “The Court of Appeal dismissed all appeals against the government - including on “noise” and “air quality” - apart from one which is eminently fixable.
"In the meantime, we are ready to work with the government to fix the issue that the court has raised. We will get it done the right way, without jeopardising the planet’s future.”
Airlines UK said the decision was “extremely disappointing”.
It added: “The economic prize is enormous if expansion is done right, with airlines ready to respond to the unlocking of new capacity by creating new routes and helping to connect the UK to new markets and destinations, and Heathrow to regions across the country.
“UK aviation has committed to net zero carbon by 2050 and this factors in the emissions created by Heathrow expansion. It is not a question of being pro-aviation or pro-environment.”
