Heathrow expansion: what are the pros and cons?

MPs will decide whether to expand Heathrow airport this afternoon, with a third runway expected to get backing from the House of Commons.

The issue has divided members of both the main parties, with Foreign Secretary Boris Johnson the most high-profile critic of the plan.

Transport Secretary Chris Grayling has said he is “cautiously optimistic” that MPs will back “the biggest transport decision in a generation”.

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The government has issued a three-line whip, ordering its MPs to vote in favour of the runway plan.

Johnson, who threatened to lie down in front of bulldozers to prevent the expansion, is conveniently missing the vote as he is abroad.

His Tory colleague Sarah Wollaston thinks Johnson should follow the lead of Chelsea and Fulham MP Greg Hands, who quit as international trade minister over the expansion. She told BBC Radio 4’s Westminster Hour that this was an opportunity for him to “actually put his money where his mouth is”.

Around 40 Labour MPs look likely to vote with the Tories, although sources have told the BBC that the SNP might vote against the expansion. Labour’s trade union backers are in favour of the expansion, putting them at odds with Jeremy Corbyn. His MPs will have a free vote on the issue.

What are the pros of expanding Heathrow?

The principal argument in favour of expanding Heathrow is to enhance the economic growth of the UK.

The independent Davies commission, found in 2015 that an enlarged Heathrow would boost UK growth by £150bn over 60 years and create 60,000 new jobs

The airport’s chief executive, John Holland-Kaye, said after the report's publication: “This debate has never been about a runway, it’s been about the future we want for Britain. Expanding Heathrow will keep Britain as one of the world’s great trading nations, right at the heart of the global economy.”

The plans would see Heathrow divided into two main passenger terminals and transport hubs – Heathrow West and Heathrow East. At 99% capacity, a three-runway Heathrow could provide up to 740,000 flights a year.

“That’s enough for Heathrow to compete on an equal footing with Paris, Frankfurt and Amsterdam and also provides sufficient hub-airport capacity until at least 2040”, says the airport.

The new runway would open by 2025 at the earliest, and Heathrow expects to be held to a 6.5-hour night flight ban as a condition of building a third runway.

What are the cons?

Environmental charities and the local authorities surrounding Heathrow “contend new evidence on the severe health impacts of air and noise pollution makes the expansion of Heathrow far less likely to pass a review”, says the BBC.

In 2016 the independent Committee on Climate Change found that the business plan for Heathrow expansion projects a 15% increase in aviation emissions by 2050.

If that increase is allowed, members said that ministers “will have to squeeze even deeper emissions cuts from other sectors of the economy” in order to abide by existing UK legislation that commits the government to cut CO2 levels by 80% of 1990 levels by 2050.

“You only have so much carbon to go round,” Tim Johnson, from the Aviation Environment Federation told the BBC. “The government will have to decide how best to distribute that; if they decide to use that for a new runway then there will have to be a hit elsewhere.”

Those in support of the expansion have also argued that Britain’s biggest airport will affect fewer people with noise in future, due to quieter planes. But government calculations last year suggested a new runway would still have a negative impact on nearly a million households, or 2.2 million people.

Department for Transport documents, released by the Civil Aviation Authority after a Freedom of Information request, show the government expects 973,000 households around Heathrow to experience increased daytime noise by 2050 after a third runway is built.