Heathrow’s third runway has been a bugbear for decades. Not anymore

The UK government was last week given two plans on how best to expand Heathrow Airport. Both included a third runway, additional terminal space and new infrastructure to handle many more flights each year.

So what? Heathrow’s CEO says that “airport capacity must be a foundation of the UK’s economic ambitions”. Rachel Reeves agrees, with an eye on job creation, trade opportunities and additional tax revenues. If a third runway is ever going to happen, it’s now. Heathrow is

• the busiest airport in Europe, despite having only two runways compared to four at Charles de Gaulle in Paris, and six at Schiphol in Amsterdam;
• running at max capacity, with new flight slots rarely made available and subject to record-breaking bids when they are; and
• hemmed in on all sides, once operating from the countryside and now in the suburbs.

Homegrown. Heathrow’s proposal centres around a full-sized third runway to the northwest of the current airport. The M25 would be diverted into a tunnel beneath the new strip, with a fresh expansion to existing terminal space to handle 66 million more passengers a year.

Young pretender. A rival plan from the Arora Group, which owns a large part of the Heathrow estate, proposes a shorter runway. The jury is out on whether this plan could accommodate aircrafts of all sizes, but it would be cheaper, quicker and less destructive to implement.

Task ahead. In either case, the expansion would be the UK’s largest airport project in a generation. Heathrow says it will learn “lessons from HS2 and Crossrail to improve supplier performance and delivery” but projects on this scale can quickly become unwieldy.

For example, runway construction is heavily impacted by the price of steel. Roughly 400,000 tonnes will be required, mainly to reinforce concrete below the tarmac. Heathrow says it will favour UK-made steel. But if domestic costs change, so too will budgets.

Climate question. The main downside of Heathrow’s third runway is environmental. More flights mean more emissions. Critics, which include London mayor Sadiq Khan, say a Heathrow expansion would undermine the government’s net zero commitments.

Way out. Rachel Reeves’s ace card is so-called sustainable aviation fuel (SAF), a refined blend of waste oils, animal fats and ethanol from corn, which the chancellor has called a “game-changer” and provided funding to research. But questions remain over the willingness of airlines to play ball, as well as

• whether enough SAF can be produced to offset carbon emissions; and
• its environmental dividend, given it emits the same amount of CO2 as normal jet fuel when burned.

Wrecking ball. Residents whose homes are under threat have lived in limbo for decades over the proposed expansion. As other London-serving airports sit in areas with more space to grow, many may ask why the government isn’t approving expansions elsewhere instead.

The comeback is that Labour is offering public support to other projects, albeit on a smaller scale, including

• Gatwick’s plans to turn its back-up runway into a fully operational second strip;
• Luton’s proposal to build a new terminal that could double annual passenger numbers;
• London City’s expansions of operations to increase capacity by 50 per cent; and
• the reopening of Doncaster Sheffield Airport.

The bottom line. Heathrow argues that it being the centre of a global aviation spiderweb makes London a more attractive hotspot for business meetings – and for business itself.

Sightseers too. Dubai International Airport is the second busiest in the world. Traffic has quadrupled in the past 20 years, in line with the growth of the Dubai tourism industry. Emirates, the state-owned airline, claims that tourism facilitated by aviation will be responsible for 10 per cent of Dubai’s projected GDP by 2030.

Lessons from history. By contrast, Heathrow is Europe’s smallest hub airport. Even though infrastructure projects are traditionally unpopular before and during construction, many are celebrated once operational (see: the Elizabeth line and the second Wembley Stadium).

That said, there’s no guarantee this will be the case with a third runway. Heathrow’s success may be imperilled not only by high passenger fees, but also by airspace system failures, the UK’s vulnerable energy infrastructure and the hot reality of climate change.