Heathrow Airport has unveiled updated plans to build a third runway by 2039 at a revised cost of £21 billion—up from £14 billion in 2018—citing “construction inflation” and growing passenger demand.
The proposal, submitted to the UK government for review, includes a 3,500-metre runway located to the north-west of the existing site. The airport has also stated it is open to considering a shorter alternative to reduce costs and complexity.
The expansion would enable Heathrow to accommodate 276,000 additional flights annually, increasing capacity from 480,000 to 756,000 flights per year. To facilitate the new infrastructure, the M25 motorway would need to be rerouted through a tunnel beneath the proposed runway.
Heathrow also plans to raise passenger capacity from 84 million to 150 million per year, with a major redevelopment of terminal infrastructure. This includes the construction of new terminals T5XW and T5XN, the extension of Terminal 2, and the demolition of Terminal 3 and the now-defunct Terminal 1.
The airport’s chief executive, Thomas Woldbye, said the time had come to push forward with the long-debated expansion. “It has never been more important or urgent to expand Heathrow,” he said. “We are effectively operating at capacity to the detriment of trade and connectivity.”
He added: “With a green light from government and the correct policy support underpinned by a fit-for-purpose, regulatory model, we are ready to mobilise and start investing this year in our supply chain across the country.”
Heathrow believes it can secure planning consent by 2029 and have the new runway operational within the following decade. The project will be privately funded, although the total cost—including terminals and infrastructure—is expected to reach £49 billion.
Budget airline easyJet, which currently does not operate from Heathrow, welcomed the move. CEO Kenton Jarvis said the expansion would offer a “unique opportunity” for the airline to serve the airport at scale and bring lower fares to consumers.
However, concerns have already emerged over potential increases in passenger charges as a means of funding the expansion—an issue raised by several airline operators.
Mayor of London Sadiq Khan reiterated his long-standing opposition to the runway. “I remain firmly against a third runway at Heathrow because of the severe impact it will have in terms of noise, air pollution and meeting our climate change targets,” he said.
Environmental groups echoed these concerns. Tony Bosworth, a climate campaigner at Friends of the Earth, warned: “If Prime Minister Sir Keir Starmer wants to be seen as a climate leader, backing Heathrow expansion is the wrong move.”
The timing of the announcement coincided with a rival plan from hotel magnate Surinder Arora. His Arora Group has proposed a shorter, 2,800-metre runway that would avoid moving the M25, reduce risk, and cut costs.
The revised Heathrow expansion plan appears to have the backing of the current government. Chancellor Rachel Reeves, who voiced her support for the project in January, said: “We are one step closer to expanding our biggest airport – boosting investment in Britain, increasing trade for businesses, and creating up to 100,000 jobs.”
Transport Secretary Heidi Alexander welcomed the proposals as “a significant step towards unlocking growth, creating jobs, and delivering vital national infrastructure”.
The next stage involves a summer review of the Airports National Policy Statement (ANPS), which will form the basis for any future development consent order application.
Conservative shadow transport secretary Richard Holden added a note of caution, welcoming the private investment but warning: “There can be no backup blank cheque from taxpayers. Britain needs infrastructure that is affordable, accountable and ambitious.”
As the debate reopens over Heathrow’s future, ministers, business leaders and environmentalists alike are preparing for another high-stakes runway decision—this time against the backdrop of economic recovery and net zero goals.
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Heathrow reveals £21bn third runway plan with potential completion by 2039
