The aviation industry’s needs

Heathrow has long argued it is in effect full, with the number of flights capped on its two runways. Its contention is that only a major hub airport, with connecting flights adding passengers from around Britain, can sustain the long-haul route network that an island nation requires, particularly in regards to trade with emerging markets and the post-Brexit environment. It is a point of view shared by many business leaders and the Department for Transport. Most international airlines want to fly to Heathrow rather than other London airports, and most cargo goes the same way.

Heathrow's third runway gets go-ahead from Chris Grayling Read more

But landing slots are at a premium, and charges reflect that – making it often too costly to make domestic routes viable. The government says more slots for regional flights are a condition of expansion, but it may have to pay large subsidies to ensure that airlines operate them. Airlines fear that charges at Heathrow will rise further and diminish competition, potentially making flying more expensive for passengers. Heathrow states that the choice is between it and rival European hubs, who would be the real beneficiaries if Heathrow was not able to expand its capacity. Opponents, however, argue that new planes are making the model of major hub airports redundant, and that more long-haul flights are possible from smaller airports.

The environment

Green campaigners have complained that the issue of climate change has been pushed to the sidelines of the debate. The Airports Commission claimed the runway and flight growth was compatible with Britain’s carbon commitments, although aviation relies on carbon trading and the promise of future technologies to achieve its sustainability targets. More immediately, air quality has taken over as the major concern. The area surrounding Heathrow has consistently breached pollution limits, largely due to the volume of traffic it sucks from motorways and along the A4. A congestion charge, more public transport links and a increased use of electric vehicles may mitigate this, but a 50% uplift in passenger numbers seems likely to make pollution worse.

Aircraft noise has abated a little with modern, quieter planes, but it remains a major concern. A third runway would bring new communities beneath flight paths. But some of those currently worst affected could win more respite if pledges are honoured on night flights, noise restrictions and the potential dispersal of incoming flights – with a new ombudsman to enforce it all. Up to £2.6bn in compensation, including for noise insulation and community amenities, will also sweeten any deal. However, about 900 homes would be demolished and and two neighbouring villages in effect destroyed.

The economics and finances

Is Heathrow's third runway really going to happen? Read more

The government has insisted that this will be a privately funded infrastructure project. Under revised calculations, the expansion would provide benefits of up to £74bn to passengers and the wider economy, as well as creating thousands of local jobs. The DfT calculates up to 114,000 additional jobs will be created by 2030 due to a third runway. Heathrow has convinced MPs, unions and business leaders nationwide that the prosperity will be shared, with jobs in Scotland and Northern Ireland sustained by exports via connecting flights.

But opponents have disputed that the costs will be borne by Heathrow alone: Transport for London has estimated that it could cost £15bn to develop surrounding transport links. That looks like more money spent on the south, just as Northern rail passengers are seeing their services decline, and electrification projects have been cut in Wales and the north.

Should the regulator keep Heathrow’s landing charges down, as airlines have demanded and the government promised, some have questioned how Heathrow – already heavily indebted – will finance its project. The Airports Commission forecast that it would be bankrolled by almost doubling its fees.