Heathrow Warns Third Runway Could Slip Four Years Beyond 2035

Heathrow Airport has warned that its £33bn third runway could open four years later than the government's 2035 target, blaming planning and regulatory hurdles that it says make the deadline increasingly difficult to hit.

The airport said on Saturday that it hopes to secure planning permission by 2029 and then open the runway "within a decade". That timeline would push the opening toward the end of the 2030s rather than the mid-decade date ministers have championed.

The Department for Transport (DfT) pushed back on the suggestion that the schedule was slipping. "The timeline has always been ambitious," a DfT spokesperson said. "We'll continue to work with promoters, including Heathrow, and all other stakeholders at pace to ensure the right framework is in place for which a planning application for a third runway could be considered."

The spokesperson added: "There is currently no live planning application for a third runway, and we cannot comment on ongoing consultation processes or prejudice them in a way that will only delay progress."

Heathrow insisted its "core scenario" had always been to open a new runway within a decade of securing planning permission, framing the 2035 date as an aspiration rather than a commitment. A spokesperson for the airport said: "It's right that ambitious targets were set; the sooner expansion begins, the sooner the whole UK will benefit."

The airport claims the benefits would involve "at least 108,000 new jobs and billions of pounds invested in supply chains in every part of the country". It described the scheme as "a national project, 100% privately financed which will support growth today and secure the UK's position in the global economy once the runway opens".

A contested project from the start

The government backed the expansion in January 2025, when former chancellor Rachel Reeves announced support for the project as a means to grow the economy. Prime Minister Andy Burnham, previously critical of the scheme, said he was "open-minded" about it when he came to office.

The runway forms part of a wider £49bn modernisation of the airport, the UK's busiest, which serves more than 80 million travellers a year across four passenger terminals and two runways.

The expansion carries heavy physical costs. Hundreds of homes would be demolished, rivers diverted, and the M25 motorway rerouted between junctions 14 and 15 through a tunnel beneath the new runway. Annual flight numbers, currently capped at 480,000, could rise to 720,000 — nearly 2,000 flights a day on average.

Opposition remains entrenched. London Mayor Sadiq Khan has consistently opposed the runway, citing noise, air pollution and climate change. Environmental campaigners and local resident groups continue to resist the project.

Climate conditions loom over the timeline

The government's climate advisers warned last week that the expansion should proceed only if airlines are required to pay for cleaner flying — a condition that could push up the cost of flights. Transport Secretary Heidi Alexander, in an interview with the Daily Telegraph published on Friday, said the advisers had set out "one view" but there was "more than one pathway to meeting our climate change obligations".

The regulatory path is itself uncertain. A draft of the planning framework for the expansion was published in June this year for consultation. Once finalised, it must go to a parliamentary vote — a step that could reportedly be delayed until 2027.

Heathrow said it was encouraged by the chancellor's efforts to streamline infrastructure delivery and remove regulatory bottlenecks, and promised to keep working with ministers, airlines and stakeholders to "progress the planning application with pace".

The warning signals that even government-backed megaprojects now hinge on planning reform. Without faster consent processes, the runway's opening — and the jobs and investment Heathrow says will follow — risks slipping well beyond the horizon ministers promised.