It seems certain now that London's airport needs will be addressed by expanding Heathrow. But it doesn't have to be that way. Here are seven alternative options to getting the skies above London moving.
1. Build a new airport in the Thames Estuary
The idea: Reclaim land in the estuary east of London and build a state-of-the-art modern airport. At the same time, completely close Heathrow, use its vast acres to build loads of new housing, which will help raise money towards the new airport. The idea's been floating about for years, with various proposals, numerous backers and even more detractors.
Pros: Backed by Foreign Secretary and former Mayor of London Boris Johnson. Despite Brexit setbacks, Boris seems predestined to serve as prime minister sooner or later and might therefore have the political clout to turn things around. Also, how cool does this look?
Cons: Backed by Boris Johnson, who seems predestined to have his name annoyingly appended to all forms of London transport. He's already bagged the Boris Bike and Boris Bus, for Pete's sake. Also, huge environmental, economic and logistical concerns make this doubtful.
2. Do nothing
The idea: The third runway at Heathrow is going to take years, maybe decades. Let's just do nothing and assume that, by then, some alternative such as teleportation, personal jetpacks or flying cars will remove the need for more air capacity. Perhaps virtual reality or World War Three will have removed the desire to travel at all.
Pros: Cheapest option in the short term.
Cons: Most expensive option in the long term. Doing nothing leads to a stalled economy; a stalled economy leads to suffering; suffering leads to the dark side. Or coach holidays to Cleethorpes.
3. Rebuild Heathrow underground
The idea: Don't encroach onto new land. The nimbys will fight you all the way. No. Build downwards. The vast complex of terminals, transport links, hangars, storage depots and other infrastructure currently occupy most of the Heathrow site. Rework the airport to put all this underground, freeing up acres of land on the surface to build new runways. Aircraft are fuelled, serviced and boarded underground only emerging for takeoff. Just like a massive aircraft carrier.
Pros: No need to stop with a third runway. The freed-up space could accommodate at least four new strips and plenty of greenery to offset some of the airport's carbon emissions.
Cons: Mahooosive cost and engineering challenge. Dreamt up by the author a few years ago, with no concept of whether such a thing is even possible. Also, it'll be a bit dark down there.
4. Put everything underground, even the runways
The idea: As above, but stick most of the runways down below as well. Planes accelerate underground, before emerging from apertures just before takeoff. A short section of runway protrudes into the open air, to allow aircraft a target for landing. Similar schemes already exist in North Korea and some place called Tracy Island.
Pros: Frees up even more land. You could then build some housing and contribute to the enormous cost. Plus, the pilots get to pretend that they're Starbuck from Battlestar Galactica, like this:
Cons: An aborted landing could be painful.
5. Build rooftop runways in central London
The idea: Actually a very old notion. Before the second world war and the subsequent advent of huge passenger planes, any number of schemes were drawn up to stick airports in central London. Plans included a dial-shaped complex on top of King's Cross station and a raised airstrip above the Thames at Westminster (above). The idea might be resurrected, with the runways straddling the roofs of new tower blocks.
Pros: Catch a flight from central London. No dicking about with the Piccadilly line.
Cons: Huge new source of toxic fumes. Dramatic increase in noise pollution. Vast swathes of the city cast into constant shadow. Greatly increased risk of a devastating plane crash in central London. Otherwise, a bit of a winner.
6. Fly aeroplanes piggyback-style
The idea: Remember how the space shuttle could be strapped onto the back of a jumbo jet for transport back to Kennedy Space Centre?
Well why don't we do that with passenger planes? That way, twice as many aircraft could take off per runway. The planes could then separate mid-air and go their different ways.
Pros: Not only doubles capacity, but looks bloody impressive.
Cons: We can think of literally no down-sides to this revolutionary idea.
7. Give lots of money to Elon Musk and let him sort it out
The idea: PayPal millionaire Musk has already landed a rocket on a barge through his company SpaceX, made electric cars sexy by founding Tesla, is championing 'hyperloop' trains that could travel close to the speed of sound, has cornered the solar power market, pushed friendly AI technologies, and is now plotting a colony on Mars. If he can free up the odd weekend here and there, we have every confidence he might be able to crack London's airport capacity problem.
Pros: Tapping in to bold, visionary leadership with a proven track record.
Cons: If, as everyone suspects, Elon Musk turns out to be a James Bond villain, we're all screwed.
Disclaimer: The above ideas are intended as a conversation piece, written from a position of total ignorance about the aviation industry, rather than any kind of serious proposal.