Chancellor Rachel Reeves confirmed her support for the project during a speech in Oxford on Wednesday morning (29 January).

"I can confirm this government supports a third runway at Heathrow and is inviting proposals to be brought forward by the summer," she said, adding the government’s aim was for formal permission to be granted "by the end of this parliament".

"Heathrow is in a unique position and we cannot duck this decision any longer," Reeves stressed.

She continued: "Heathrow is at the heart of the UK’s openness, around three-quarters of all long-haul flights in the UK go from Heathrow."

Reeves reiterated the airport currently accounts for 15 million business travellers a year. "A third runway could increase GDP by 0.43% by 2050 and could create more than 100,000 jobs."

She confirmed surface transport work, which will likely include putting the M25 into a tunnel, "must be privately financed" and the project must fall in line with environmental commitments on noise, carbon emissions and local air quality.

Reeves added decisions on expansion at Gatwick and Luton airports – part of a major effort to grow the UK’s economy – would be made by transport secretary Heidi Alexander in the next few weeks.

The chancellor also pledged her support for reopening Doncaster Sheffield airport and for a logistics park at East Midlands airport, creating 2,000 jobs.

Reeves’ backing for expansion at Heathrow comes nearly two decades after the party made a similar pledge when it was last in power.

Heathrow argues it is currently operating very near 100% capacity, serving 84 million passengers a year, and needs to expand to reclaim its crown as the world’s busiest hub airport.

The basis of most arguments for expansion at Heathrow is economic growth, but detractors say expansion flies in the face of the UK’s commitments on climate. Energy and net zero secretary Ed Miliband has said expansion must be achieved within the UK’s carbon budgeting.

More locally, expansion at Heathrow would have significant impacts for residents local to the airport.

Even if backed, there are many more hurdles to clear, and it’s unlikely construction would start for at least another decade, so the government is banking on its backing demonstrating its commitment to growth.

The decision has prompted reaction from both sides of the argument. Abta chief executive Mark Tanzer welcomed the government’s support for airport expansion, while stressing it was important to be mindful of existing green commitments.

"To deliver growth in aviation while meeting environmental goals, we need government support – both in policy and finance – to help the industry develop solutions, such as developing a domestic sustainable aviation fuel industry," he said.

Tanzer added: “The travel industry is making good progress in these areas, but the decision on airport expansion today brings back into focus the need for the sector to work with government so that we both deliver growth and contribute to the UK’s roadmap to net zero.”

However, Alethea Warrington, head of aviation at climate charity Possible, branded the announcement “economically illiterate”. “The chancellor wants to boost growth, but new runways won’t strengthen our economy. Bigger airports will only benefit a tiny group of frequent flyers, while worsening the UK’s massive tourism deficit."

Tim Alderslade, chief executive of Airlines UK, which represents UK-registered carriers, highlighted the possible cost to carriers. “Airlines support more airport capacity to grow the economy and foster trade, but expansion must be affordable, improve operational resilience for passengers and freight, and be compatible with our net zero commitments,” he said.

A Virgin Atlantic spokesperson also expressed concern about the cost of the project and of operating at “the world’s most expensive airport with service that falls short”.

“We are supportive of growth and expansion at Heathrow, if, and only if, there is fundamental reform to the flawed regulatory model to ensure value for money for consumers, affordability for UK plc and support a competitive UK aviation industry," they said.

However, easyJet chief executive Kenton Jarvis has said the airline would be interesting in basing aircraft at Heathrow if more capacity was available.

“Expansion at Heathrow will provide consumer and economic benefits and represents a unique opportunity for easyJet to operate from the airport at scale for the first time and bring with it lower fares for consumers," he said.

From the agency side, Julia Lo Bue-Said, Advantage Travel Partnership chief executive, said: “We’re pleased to see the government supporting essential infrastructure growth across several of the UK’s major airports including the third runway at Heathrow.

"These expansions will significantly improve the passenger experience for both leisure and business travellers with a wider range of departures, increased competition for pricing, and reduced congestion and delays. Alongside this, it will enhance connectivity to global markets, driving both tourism and business investments.” 

Meanwhile Karen Dee, chief executive of AirportsUK, the trade association for UK airports, said: “Airports make an enormous contribution to the economy, connecting businesses, facilitating imports and exports, bringing in investment and creating jobs. Expanding capacity will support growth in all these areas and will not come at the expense of our sustainability goals.

“New, cleaner fuels, more efficient and quieter aircraft, decarbonised airport operations and modernisation of our airspace will all ensure aviation is able to meet its obligations alongside growth.”

There was also support from the CAA: Rob Bishton, chief executive, added: “Expanding the sector will give passengers more choice and build resilience as well as contributing to the UK’s productivity.”