But now, 17 years since the previous Labour government voiced its support for expansion, the issue is back on the agenda.

And on Wednesday (29 January), the party – now back in government – gave its support for expanding Heathrow for a second time.

Government signals support for Heathrow airport expansion

It’s likely to be good news if you’re involved in the aviation sector, or a regular traveller frustrated at circling the skies above southern England due to airspace congestion.

However, any of the 10,000 residents expected to be displaced by enlarging Heathrow will take a different view, as will campaigners who believe airport development is at odds with greenhouse gas reduction.

So what are the issues at stake for Heathrow, London’s airports and the wider UK aviation sector, as well as those whose lives either rely on or are fundamentally impacted on daily basis by these airports?

What’s happened on Wednesday?

During a speech in Oxford on Wednesday (29 January), the chancellor of the exchequer, Rachel Reeves, confirmed she is in favour of expanding the UK’s airport capacity, including building a third runway at Heathrow.

She said decisions on expansion at Gatwick and Luton would follow in the coming weeks, while she also said she was behind efforts to reopen Doncaster Sheffield airport.

Does this mean anything will actually happen?

Immediately, no. There will be significant legal challenges, and perhaps a few resignations among MPs opposed to Heathrow’s enlargement. Don’t expect spades in the ground for a decade.

And if the bulldozers do eventually move in, it will likely take until the 2040s for construction to finish and for new capacity at Heathrow to come online.

What are the arguments for a bigger Heathrow?

Heathrow currently operates at near-100% capacity and processes 84 million passengers and 1.5 million tonnes of freight, with around 1,300 aircraft movements each day.

The airport long ago lost its crown as the world’s busiest international hub to Dubai and, while it may never regain it, a third runway would reduce the time aircraft spend taxiing for take-off or stacking in the air waiting to land.

Plus, in simple terms, more passengers – particularly more business travellers – and more freight equal more income for UK plc. Heathrow is currently capped at 480,000 departures a year, but a third runway could potentially increase this to 720,000, according to the BBC.

The government says pollution concerns will in future be allayed with the development of sustainable fuels, but these do not mitigate local emissions.

EasyJet, meanwhile, has said expansion at Heathrow could create opportunities for it to base aircraft at the UK’s largest and busiest airport.

And the arguments against?

The noise and pollution for residents would increase massively. To build a third runway, the villages of Harmondsworth, Sipson and Harlington would be decimated.

The airport hotels to the north of Heathrow and several listed buildings would also be destroyed. Perhaps more worryingly for the government in terms of cost and disruption, rivers would need to be diverted and the M25 put into a tunnel. Expansion also seems at odds with the UK’s net-zero ambitions.

Any voices of dissent within government?

Yes. Energy and net zero secretary Ed Miliband told parliament this week: “I just want to sort of provide this element of reassurance to you, which is 100% any aviation expansion must be justified within carbon budgets, and if it can’t be justified, it won’t go ahead."

What will it cost – and who will pay?

The consensus appears to be up to £63 billion, with airlines asked to contribute. That inevitably means fare increases, with Heathrow already having the world’s highest passenger fees at £23.73.

Heathrow’s investors will also be asked to put their hands in their pockets, which may cause some friction. But some, like Qatar’s sovereign wealth fund, which owns 20% of Heathrow, and Saudi Arabia’s, which owns 15%, have deep pockets.

Haven’t we been here before?

Yes. Heathrow expansion was first raised by Tony Blair’s government and famously, before he became prime minister, Boris Johnson threatened to lay down in front of the bulldozers.

The pandemic meant it didn’t come to that, with Heathrow’s third runway plans disappearing like kerosene vapour, but the indications so far are that despite being more sympathetic to the environmental movement, the new government also appears to be amenable to more flights.

What about Gatwick?

Gatwick has submitted plans to bring its reserve runway into regular use, potentially doubling capacity to 78 million annual passengers. A decision is due by 27 February, with the nod more likely to be given if Reeves looks favourably on airport expansion in general.

The Sussex airport’s application is less about massive redevelopment – “most” of the building required would be within current boundaries, it argues – and more about a huge increase in passenger numbers, which would lead to more flights, noise and air pollution.

London airports ’ready to steal a march on Heathrow’

Gatwick is offering a legally binding agreement on its future noise envelope if development is permitted, but campaign group Communities Against Gatwick Noise Emissions (Cagne) points out “they are not offering any similar legally binding assurances to protect residents from air pollution”.

Cagne has said it will seek a judicial review in the high court if transport secretary Heidi Alexander approves plans.

And what about Luton?

Luton wants to increase passenger numbers from the current 19 million to 32 million by the mid-2040s. To do this, it needs a new terminal and new taxiways to enable more efficient use of its single runway. A decision is due on 3 April.

Part of the application includes a vast new long-stay car park with “emissions-based access and parking charges” to encourage greener travel. One potential stumbling block is that plans encroach on Wigmore Valley Park, which Luton admits “is upsetting to many”. It plans to alleviate this by constructing a new park “at least 10%” bigger and further from the runway.

Luton may have a tough battle on its hands, as the park houses wild orchids, plus “hundreds” of trees, according to campaign group Stop Luton Airport Expansion. It is also the site of old landfill and there are concerns about disturbing polluted soil.

The group also claims Luton is the fourth most congested town or city after London, Birmingham and Manchester and so not suited to airport expansion.

Why not just expand Gatwick and Luton?

You could argue combining the proposed growth across Gatwick, Luton and other airports – Stansted and London City have their expansion ambitions too – would add sufficient capacity for the London area.

Stansted already has the go-ahead to expand from 29 million to 43 million annual passengers, and to 51 million from 2040.

Together, these would exceed the extra 54 million passengers an expanded Heathrow would handle, but proponents argue Heathrow needs to retain its hub airport status, which others cannot match.