Heathrow's Third Runway Slips Toward 2039 as Planning Hurdles Mount

Heathrow Airport has signalled that its long-awaited third runway could be pushed back to 2039, four years later than the timetable ministers had been working towards. The airport said planning and regulatory obstacles are making the government's original 2035 opening target increasingly hard to meet.

The west London hub, which handles more than 80 million passengers a year through four terminals and two runways, now expects to obtain planning consent by 2029 and to bring the new runway into service within a decade of that approval. That would place the opening around 2039 rather than the mid-2030s.

The project carries an estimated price tag of £49bn and has been billed as one of the most significant pieces of national infrastructure in decades. It is also unusual in being entirely privately financed, meaning taxpayers would not directly fund the construction.

Heathrow said its "core scenario" has always been to open a new runway within ten years of securing planning permission. It added that it was encouraged by the chancellor's efforts to streamline infrastructure approvals and remove policy and regulatory bottlenecks, and pledged to work with ministers, airlines and other stakeholders to move the planning application forward quickly.

The Department for Transport responded that the project's timeline had "always been ambitious". A spokesperson noted there is currently no live planning application for a third runway and said the department could not comment on ongoing consultation processes in a way that might prejudice them and cause further delay. Officials said they would keep working "at pace" with promoters and stakeholders to put the right framework in place.

The government's backing for expansion was announced by former chancellor Rachel Reeves in January 2025. Prime Minister Andy Burnham, who had previously been critical of the scheme, said after taking office that he was open-minded about it. That political shift gave the project momentum, but the practical mechanics of approval have proved slower than supporters hoped.

A public consultation on the expansion was published in June this year. Once the consultation is finalised, the plan must still go to a parliamentary vote, which has reportedly been pushed back to as late as 2027. That parliamentary stage represents another potential source of delay before construction could even begin.

Supporters point to the economic case. Heathrow says expansion would generate at least 108,000 new jobs and channel billions of pounds into supply chains across every part of the country. The airport describes the scheme as a national project that will support growth now and safeguard the UK's position in the global economy once the runway opens. Earlier estimates cited around 100,000 jobs.

The operational changes would be substantial. Flights from Heathrow are currently capped at 480,000 a year. Under expansion, that ceiling could rise to 720,000 annually, equivalent to nearly 2,000 departures and arrivals on an average day. Such a jump would reshape schedules for airlines and alter the airport's role in European and long-haul aviation.

The physical footprint of the project is equally contentious. Hundreds of homes would be demolished, rivers would be diverted, and a stretch of the M25 between junctions 14 and 15 would be rerouted through a tunnel beneath the new runway. Those works would affect communities in neighbouring areas and require years of construction coordination.

Opposition has been vocal. Environmental campaigners and local resident groups have long fought the plan, citing carbon emissions, noise and damage to green belt land. London Mayor Sadiq Khan has consistently opposed the expansion, warning about its impact on noise, air pollution and climate change. In September, he described the proposal as an "outdated" risk.

The delay announcement also follows separate advice that a third runway should only proceed if airlines bear the cost of cleaner flying. That recommendation, reported earlier in September, reflects growing pressure on the aviation sector to reconcile growth with decarbonisation targets. Heathrow's management has argued that expansion can be compatible with emissions reductions if supported by sustainable aviation fuel and modern aircraft.

For now, the immediate bottleneck is procedural rather than financial. Without a live planning application, no formal examination can begin, and the consultation must conclude before a parliamentary vote can be scheduled. Each stage adds time, and Heathrow's revised language suggests it no longer believes the 2035 target is deliverable under current rules.

The airport's stance places renewed pressure on ministers to deliver the promised streamlining of infrastructure planning. If the government can accelerate approvals, Heathrow believes a 2029 consent date remains feasible. If not, the runway could slip further still, delaying the economic benefits that proponents have promised for more than a decade.