Noora Mykkanen and
Craig Munro
Published November 25, 2025 12:51pm
Updated November 25, 2025 12:51pm
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Heathrow has now submitted its latest plan for the expansion, which would divert part of the M25 motorway (Picture: Heathrow Airport)
The controversial expansion of Heathrow Airport has reached a new milestone, with the government officially backing a plan that would take a chunk out of the nearby M25.
Transport Secretary Heidi Alexander said the successful proposal, which came from the airport’s owners, is the ‘most credible and deliverable option’ for a third runway.
Heathrow previously described its plan as ‘shovel-ready’ and said flights could take off in the next decade.
The new runway could add 276,000 more flights each year, increasing the number from 480,000 to 756,000 annually.
The expansion would create at least 30 new daily routes and serve up to 150 million passengers, Heathrow said.
Alexander cited the ‘relative maturity’ of the airport’s proposal, as well as the ‘stronger comfort it provides in relation to the efficient, resilient and sustainable operations of the airport over the long term’.
She noted the scheme ‘requires major works to the M25’, but added that the rival plan from Arora Group would also have a ‘considerable impact’ on the motorway – one of the UK’s busiest roads.
A map shows where the new terminal complex T5X, consisting of terminals called T5XN and T5XW terminals, and the third runway would be built if Heathrow’s plan is chosen (Picture: Heathrow)
Here is a breakdown of the £49 billion price tag:
- £21 billion -Used to build the new, full-length, 11,482ft runway north-west of the current airport, and to divert part of the M25 into a tunnel
- £12 billion – This will fund the new terminal complex called T5X to allow the increased passenger numbers, baggage handling, airside and landside operations, car parks and transport connections
- £15 billion – The current airport buildings and services will be upgraded at Terminal 2, including two satellite piers, while the old Terminal 3 and Terminal 1 will be demolished
Reaction to the expansion plan
The third runway will swallow up parts of Harmondsworth in Hillingdon north of the airport, an area dotted with hundreds of homes, a primary school, pubs and a moor.
Part of the M25 will be diverted into a tunnel to cut underneath the runway.
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Many locals are against the expansion as homes and businesses near the airport’s safety perimeter face demolition, with up to 700 buildings at risk.
This aerial CGI visual shows where the third runway would be built above the existing north runway and across the M25 (Picture: Heathrow Airport)
The UK’s busiest airport has been driving for the expansion for years as bosses have argued that Heathrow’s capacity is full.
Heathrow’s CEO, Thomas Woldbye, said operating at capacity at the moment is ‘to the detriment of trade and connectivity.’
He said: ‘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.’
Chancellor Rachel Reeves has argued the move will help boost UK economic growth, but campaigners have said the expansion will result in more aircraft noise and pollution.
Opposition to the idea from environmental groups has been fierce since it was first introduced in 2009.
A CGI visual shows the new third Heathrow runway on the left with the M25 diverted underneath it (Picture: Heathrow Airport)
Greenpeace UK said the expansion will support a small number of flyers while ‘the rest of us have to live with the consequences of their disproportionate polluting’.
Justine Bayley, the chair of Stop Heathrow Expansion and a local resident, told Metro that the government failed to give any of the ‘downsides,’ adding that the Chancellor gave ‘fairly meaningless assurances that all environmental aspects will be met.’
She said she has seen ‘all sort of threats coming and going’ during her 30 years of living in the village and that the residents would continue their fight against the expansion.
Ms Bayley said the country has ‘managed a fair bit of growth without the additional runway.’
‘It is not a magic wand for growth,’ she said.
Heathrow Airport in numbers
Heathrow is one of the world’s busiest airports as planes take off or land up to every 45 seconds across the two existing runways.
It is set to see 84.2 million passengers pass through its terminals this year – an increase of 0.4% from the 83.9 million last year.
Two existing runways have capacity for around 475,000 flights. The new runway would raise the capacity to around 740,000 flights.
Around one-third of the UK’s long-haul flights go through Heathrow, Chancellor Rachel Reeves said.
She said the expansion could create more than 100,000 jobs.
Alongside long-haul routes, the new runway would serve flights to domestic locations like Belfast International, Liverpool, Prestwick and Durham Tees Valley.
However, easyJet, which doesn’t currently serve Heathrow, said the expansion is a ‘unique opportunity for easyJet to operate from the airport at scale for the first time and bring with it lower fares for consumers.’
Colne Valley Regional Park said it is ‘fiercely opposed’ to the expansion, claiming that it would result in the ‘unprecedented environmental destruction’ and loss of swathes of the park located near northwest of the airport.
The group said that five rivers would need to be diverted along with the M25 and local road changes.
Heathrow is the UK’s and Europe’s busiest airport, with passenger numbers forecast to reach 84.2 million this year (Picture: Story Picture Agency/REX/Shutterstock)
Independent advisers on the Government’s Climate Change Committee recommend there should be ‘no net airport expansion across the UK.’
The UK is committed to reaching net zero for CO2 emissions by 2050.
Chancellor Reeves has argued that growth does not need to mean compromising the net zero target, saying that the Heathrow expansion is ‘badly needed.’
The expansion has caused division in the government, with Ed Miliband spending years campaigning against the project before he made a U-turn and backed the proposal.
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Mayor of London Sadiq Khan has been clear about it opposition to the expansion due to the ‘severe impact it will have in terms of noise, air pollution and meeting our climate change targets.’
When will Heathrow’s third runway open?
It will take years before the third runway and new terminals are operational as the planning process will take up to two years before anything can be built.
The third Heathrow runway is not expected to open until the 2030s.
This article was first published on January 29.
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