However profitable it may turn out to be, the idea of a four-runway Heathrow is already being disputed by anti-expansion campaigners. John Stewart of HACAN goes for intentional understatement when he describes Heathrow's estimates as "hugely optimistic." He also points out that flight demand could be drastically reduced if oil prices rise or the industry's tax breaks are curtailed. HACAN and other skeptical groups support more incremental upgrades to London's Gatwick and Stansted airports as a means to reduce Heathrow’s burden.

A visionary architect and a floppy-haired mayor unite to offer an ambitious alternative

London Mayor Boris Johnson has advanced a far more radical plan for the outright replacement of Heathrow with a multi-runway hub airport to be built atop a man-made island in the estuary of the River Thames. He has since moved to support an alternative plan, authored by renowned architect Sir Norman Foster, that pitches a similar four-runway behemoth to take over Heathrow’s role of primacy. Among the key benefits touted by these plans is a lower noise impact, allowing the airport to operate 24 hours a day, plus a cohesive layout that would cut flight connection times down to 45 minutes.

The cost of the Foster + Partners bid is estimated at £24 billion ($37BN), which the designers claim can be raised through private investment, with the project becoming partially operational in 2029. Accounting for all potential economic benefits, the Thames Hub Airport would deliver £75 billion ($116BN), paying off its initial costs within the first decade. These numbers don’t compare well to the projected timescale or revenues of a Heathrow expansion, however they’re also not subject to the same burden of widespread public disapproval.

Gatwick and Stansted offer the most modest ideas, with the former airport asking for a frugal £9 billion ($14BN) to get a new runway up and running by 2025. The vision is for London’s air traffic to be redistributed among "a constellation" of competing airports, which is expected to result in up to £56 billion ($87BN) of economic growth. As Mayor Johnson’s competing proposal points out, however, fragmenting London’s air connectivity in that fashion would deprive the city of its ability to function as a hub for connecting flights — which it is ideally positioned to do given its centrality in the developed world.

In 2012, close to one percent of the world’s population passed through Heathrow

The alternatives to Heathrow are numerous, varied, and in some ways preferable, but they may already be irrelevant. The Financial Times reported this week that none of the major airline alliances currently operating out of Heathrow are willing to move away. SkyTeam, the Oneworld Alliance, and the Star Alliance — among whose members you’ll find Delta, United, Swissair, Lufthansa, and both British and US Airways — are all equally resolute in their commitment to Heathrow. The FT also notes that SkyTeam has already declared that "relocating to another London or UK airport is not an option for our members."

The independent Airports Commission will offer its preliminary report on the various pitches for air capacity expansion by the end of this year. It’ll suggest incremental strategies to cover the UK’s short- and mid-term aviation goals, but the Commission’s final assessment will be reserved until summer 2015. With Heathrow’s established cachet as a global brand, improving customer satisfaction ratings, and almost universal airline support, that 2015 report is shaping up to recommend a future that looks like a bigger version of the present.