Prime Minister Andy Burnham told the BBC at the opening of the Labour Party's annual conference that he would not support Heathrow's third runway until the views of residents near the airport are fully heard. He added that the decision should belong to London, not the national government.
Burnham's stance reverses the 2023 endorsement from former Prime Minister Keir Starmer, who signed off on the expansion last year after a national consultation.
Heathrow now operates at about 99% of its capacity, a figure that rivals only major European hubs with multiple runways. The airport sits 15 miles west of central London, making its expansion a national issue.
Residents in the Hounslow and Isleworth areas have long protested the plan, citing noise, safety risks from flights over densely populated zones and rising carbon emissions. Emma Patel, a mother of three from Hounslow, said, "We can't afford the extra noise or the risk of an accident over our homes."
The FAA says the project could be delayed by four years, pushing the runway's operational date beyond 2039. The government will now launch a fresh consultation process by the end of June, after which a detailed planning application will be submitted to the Secretary of State for Transport.