Will The London Heathrow Airport Third Runway Ever Be Built?
By The Aviation Hub
5 min read
Updated September 27, 2026 
London Heathrow Airport has confirmed what many in the industry already suspected.
The third runway will not open in 2035.
Heathrow has told the Government that the earliest realistic date is now 2039, a delay of four years to a project that has been debated in some form since the 1940s.
The admission, first reported by Sky News, lands at an awkward moment.
Within 24 hours, Prime Minister Andy Burnham declined to endorse the scheme at all.
So the question London has been asking for decades returns with fresh force.
Will this runway ever actually be built?
Why London Heathrow Has Pushed Back To 2039
The 2035 target was always political rather than practical.
Rachel Reeves set it in January 2025 when she threw the Government’s weight behind expansion as part of her growth agenda.
Heathrow now says that date was “unachievable” under the current planning and regulatory system.
The airport’s position is simple.
It aims to secure planning permission by 2029, and it expects the runway to open within a decade of that consent.
A Heathrow spokesperson said: “Our focus has always been to secure planning permission by 2029. Once achieved the runway will be open within a decade.”
The Department for Transport did not dispute the new date.
A spokesperson said the timeline “has always been ambitious” and that officials would keep working with Heathrow “at pace”.
That is hardly a vote of confidence in 2035.
The Scale Of The London Expansion Plan
This is no ordinary runway project.
The wider programme carries a £49 billion price tag, made up of around £15 billion of upgrades already planned and roughly £33 billion for the runway, new terminal capacity and associated infrastructure.
In November 2025, ministers selected Heathrow’s own northwest runway scheme over a cheaper rival from Arora Group.
ITV News reported that the plan moves the M25 around 130 metres west, with the motorway passing through a tunnel beneath the new runway.
That element alone is costed at about £1.5 billion.
Hundreds of homes would be demolished.
Rivers would be diverted.
Heathrow says capacity would rise to around 756,000 flights and 150 million passengers a year.
The airport insists the project is entirely privately financed and would support more than 100,000 jobs across the UK.
A London Airport Running Out Of Room
The commercial case has not changed.
Heathrow operates at close to 99% of its capacity with just two runways. Paris Charles de Gaulle and Frankfurt each have four.
Amsterdam Schiphol has six.
That constraint shapes everything about London’s hub.
Airlines cannot add new long haul routes without buying slots from someone else. Regional UK airports lose domestic links to the capital.
Carriers based in Paris, Frankfurt and Amsterdam happily absorb transfer traffic that London cannot handle.
For cargo, the picture is similar. Heathrow is the UK’s largest freight airport by value, and almost all of that cargo flies in the bellies of passenger aircraft.
No new runway means no meaningful growth in belly capacity for another decade at least.
The Planning Hurdles Still Ahead
The route to consent remains long.
The Government published a draft Heathrow Expansion National Policy Statement in June 2026, and the public consultation closed on 1 September.
According to the Department for Transport, expansion must meet four tests covering climate, air quality, noise and economic growth.
Parliament must then approve the final policy statement.
Only after that can Heathrow submit its development consent application, which will face a full examination before any decision in 2029.
Every stage invites legal challenge.
London has seen this before. Parliament backed a third runway in 2018, only for the Court of Appeal to rule the policy unlawful in 2020 over climate commitments.
The Supreme Court overturned that ruling later the same year, but the pandemic had already frozen the project.
Political Winds Over London Have Shifted
The biggest threat to the runway may no longer be the courts. It may be Downing Street.
Keir Starmer’s government backed expansion firmly.
His successor is far more cautious. Speaking at Labour’s annual conference, Andy Burnham told the BBC: “I think, principally, it’s a matter for London. I think you’ve got to hear the voice of people there first.”
That is a notable shift. London Mayor Sadiq Khan has opposed the third runway for years and has previously threatened legal action against it.
Framing the decision as one for London hands opponents a powerful argument. Reeves, the minister who championed the 2035 date, is also no longer at the Treasury.
Climate concerns have not gone away either.
The Climate Change Committee has repeatedly warned that airport expansion must fit within the UK’s net zero pathway, and campaigners will test that point in court.
The Gatwick Factor
There is also an alternative taking shape.
The Government approved Gatwick’s plan to bring its northern runway into routine use in 2025.
That scheme is cheaper, faster and far less disruptive.
It will not replace a hub.
Gatwick serves a different market, with fewer transfer passengers and less long haul cargo.
But it does give ministers a way to add capacity to London’s airport system without the political pain of Heathrow.
So, Will It Ever Be Built?
The honest answer is that nobody can say with confidence.
The engineering is feasible and the money is private. The demand is not in question. What remains uncertain is political will, and that has collapsed before.
Gordon Brown’s government approved a third runway in 2009, only for the coalition to scrap it in 2010.
A 2039 opening now depends on a clean run through Parliament, a planning consent by 2029, survival in the courts and a Prime Minister willing to see it through.
That is a long list of conditions for a project that has failed to clear them for more than half a century.
The Aviation Hub’s view is that expansion at London Heathrow remains more likely than not in the long term, simply because the capacity problem will not go away.
But 2039 looks like a best case rather than a firm date. London has heard “this time it is different” before, and passengers should not book their first flight from Runway Three just yet.
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