OVER the weekend, several newspapers suggested that Britain's Conservative government will finally be making a decision on where to build a new runway for London and the South East of England. This has become an urgent issue as the two runways at Heathrow, the capital's biggest airport, have been operating at more than 98% capacity since 2003 and cannot add any more flights or routes. In spite of this, aviation capacity is an issue that politicians have perennially kicked into the long grass. No new full-length runway has been built in the South East since the second world war. Mainly due to opposition from local residents, plans to increase airport capacity have repeatedly been shelved: at Cubbington in Buckinghamshire in the 1960s, at Foulness in the Thames Estuary in the 1970s and several attempts to build a third runway at Heathrow in the 2000s. The current two options which the government is deciding between are a third runway to the north west of Heathrow and a second runway at Gatwick airport, to the south of London. Earlier this year, the commission set up to recommend which the government should choose came out in favour of Heathrow. The case for it is largely based on the idea that hosting a hub airport, connected to a large number of destinations and with much through traffic, would benefit Britain's economy more than simply building the same amount of extra capacity at a smaller airport such as Gatwick. Pooling passengers from many different points of departure, boosters argue, makes it possible for airlines to offer flights to places that would otherwise be uneconomic.

But as we pointed out in a briefing back in 2013, academic research suggests that the additional economic benefits of a city having direct links to lots of destinations has been overstated, compared with just adding more capacity:

...there is a surprising lack of evidence to support the common assumption that direct connections to lots of cities boosts economic growth. Adie Tomer of the Brookings Institution, an American think-tank, says research shows that a big flow of arriving and departing passengers, rather than the number of destinations reached, is what boosts growth. Take for example a recent study of American cities by Zachary Neal of Michigan State University, which looked at jobs in the creative industries. The number of other cities to which the cities’ airports connected directly appeared to have no relevance; what mattered, as earlier research had suggested it would, was the sheer flow of passengers in and out of a city.

There are two possible explanations for this. The first is that investment goes to cities that are attractive in their own right, rather than because they are easy to get to for businessmen. The second is that air travellers do not mind having to connect flights in a foreign hub as much as they did in the past, because it is now easier to work on the go using tablet computers, smartphones and the like.

That, in theory, should damage Heathrow's economic case for expansion, and boost Gatwick's. But there is a feeling that central government may already have been persuaded of the wisdom of expanding the country's main hub, particularly as the political headwinds have now swung around to its advantage.

E

xpanding Heathrow, it was assumed, would damage the fortunes of Conservative MPs in several marginal

constituencies near Heathrow. It would also tarnish Zac Goldsmith's campaign to succeed Boris Johnson as mayor of London in May 2016. But, with the

opposition Labour party suddenly in such disarray,

it may feel that it can now push ahead with

Heathrow expansion, as proof of its commitment to growth-boosting infrastructure projects, without the the collateral damage in those Tory seats that would be directly affected.

There is plenty of time for more twists. Earlier today, MPs on the environmental audit committee released a report suggesting that the government should not propose a third runway at Heathrow until it could guarantee that legal air pollution levels would not be exceeded. It also recommended a ban on night flights. Such restraints may not prove practical. Heathrow remains favourite to get the nod for the new runway, but there are still many battles ahead.