Heathrow has been given the go ahead to press forward with plans for a third runway that will bring in hundreds of thousands of extra flights to the airport every year, the Chancellor has announced – but questions remain about how deliverable the project will be.

The airport has long pressed for a third runway. The plans  in the past have involved demolishing the mediaeval village of Harmondsworth and its neighbours Sipson and Harlington.

Feasibility studies have also been carried out about re-routing the M25 through a tunnel under the new northern runway and the enormous infrastructure project is supposed to be built while the country meets its environmental targets.

Heathrow has welcomed the Chancellor’s announcement today that the Government is backing a third runway and would be inviting proposals to be brought forward by the summer. 

The Government has already tightened legal pathways against any plans, cutting the number of appeals allowed from three down to just one.

Opponents, including the London Mayor’s office, MPs and campaign groups however, argue a third runway won’t bring in hoped-for economic benefits but will raise “serious environmental and health concerns”.

The Mayor of London, Sadiq Khan, said: “I remain opposed to a new runway at Heathrow airport because of the severe impact it will have on noise, air pollution and meeting our climate change targets.

“I will scrutinise carefully any new proposals that now come forward from Heathrow, including the impact it will have on people living in the area and the huge knock-on effects for our transport infrastructure.

“Despite the progress that’s been made in the aviation sector to make it more sustainable, I’m simply not convinced that you can have hundreds of thousands of additional flights at Heathrow every year without a hugely damaging impact on our environment.”

Stanwell Moor is the Surrey village at the end of Heathrow’s southern runway. 

Residents there have grown used to jet engines flying overhead. So much so that some regard the noise made from incoming planes a respite compared with the roar when taking off.

The Stanwell Moor Residents’ Association, in a statement published on its website, said: “What is different this time is that easterly alternation planning application will go ahead regardless of the airport expansion and would lead to more flights over our village; and secondly, the Government are likely to reform planning to speed up the approval for expansion. 

“We will be ready to represent the village with a list of demands that put residents first.”

The Government said it would issue a full assessment of any expansion plans through the Airports National Policy Statement.

It said the project must represent value for money and that it, plus any associated service transport costs, will be financed through private funding to “ensure that a third runway is delivered in line with our legal, environmental and climate objectives.”

Surrey County Council and Spelthorne Borough Council have both been approached for comment. 

The Liberal Democrats issued a statement from its MPs saying the third runway would jeopardise the UK’s climate commitments and will have a significant negative impact on local communities and human health. 

The hundreds of thousands of extra flights to-and-from Heathrow, they said, will increase the risk of health conditions including heart disease, strokes and mental health issues. 

MP for Esher and Walton Monica Harding said: “A third runway at Heathrow would have a profound impact on our climate, health, and communities. With a lack of clarity on the economic benefits and costs to the taxpayer, along with serious environmental and health concerns, the Government must urgently address these questions.” 

Others, such as the Chartered Institute of Logistics and Transport UK were quick to praise the announcement but cautioned the importance of prioritising environmental concerns. 

Its chairperson, Paul Le Blond, said “Any expansion strategy must prioritise public transport integration, leveraging existing transport hubs and accommodating new rail links. 

“The development should include modernised terminals and new gateway facilities for both the northern and southern perimeters. Crucially, all environmental impacts—including noise, local air quality, and greenhouse gas emissions—must remain within statutory limits.

“Whilst the expansion would be privately funded through passenger and shipping revenues, government support through policy frameworks and strategic rail investment will be essential to unlock private sector investment.”