How About We Rebuild Heathrow Airport Underground?

By M@ Last edited 57 months ago
How About We Rebuild Heathrow Airport Underground?

The thorny problem of how best to increase London's air capacity is some way from being solved (assuming, here, that we do need to increase capacity — that's another argument). Should we expand Heathrow, focus on other airports, or build afresh somewhere in the Thames Estuary? There are huge downsides to all of the proposals.

Recently, Heathrow set out its own schemes for a third runway. All options involve compulsory purchase of land, demolition of properties and the introduction of new approach paths over other properties. In short: less than ideal.

But here's a mad idea that could expand the airport without any new land acquisition. Build downwards.

The existing two runways sandwich a strip of land about 2.5 miles long and half a mile wide. It's used for taxiing, terminals and other infrastructure. Does this all need to be above ground?

The current set-up, with huge amounts of space devoted to terminals and taxiing. From Google Maps.

Vast hangars and tunnels could be built beneath this space, using the local expertise gained on Crossrail, super-sewer digs and other large subterranean projects. The reclaimed surface land could be used to build two new runways, potentially doubling capacity. The planes would remain underground, waiting their turn for take-off, before emerging onto the tarmac for flight. Think of it as a super-sized aviation version of Canary Wharf tube station, or a civilian scale-up of an aircraft carrier's hangar bay.

Mock-up of a four-runway Heathrow, with services underground. A strip remains in the middle for future expansion.

All of this, of course, would come at significant cost. But so would building a new airport in the Estuary.

Maybe we could go even further and also build the runways underground, with brief apertures at either end to allow the planes to land and take-off. It sounds madcap (and it is), but it's not unprecedented. Putting everything underground would also free up huge tracts of land on the surface, which might be sold off to part-fund the project.


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!

See also: Our April Fool's piece on piggy-back planes into Heathrow.

Last Updated 18 July 2013

Mark Walley

How well do airplanes cope taxing up and down slopes? If they don't, that's not the end of the world, we'd just have to install conveyor belts large enough to carry airplanes. In fact, that's probably reason enough to do it.


when i first saw this i thought the idea was to put the new runway underground. suppose it worked in thunderbirds


Think of the noise! and the fumes!


Isn't one of the major issues the volume of air traffic flying straight over London, and the accompanying noise, which would obviously rise with this scheme?

Here's something else I was wondering, however. I know that planes have to approach Heathrow from the east because of the wind, but is there any reason why the runways couldn't be angled - say 45 degrees, or even 30? Right now they run east-west, but if three runways were angled it could reduce the area of London affected. Apparently the original runways were angled.

Richard Knott

Hmm, Might still be enough room for the planes to remain on the surface, but move all the terminal buildings underground. We've had Aircraft carriers for nearly a century, same principle


It would be like birmingham international station crossed with arc royal (minus train spotters and sailors)

Roger Manser

Talking of Heathrow and Undergrounds, we need a fast tube link to Heathrow - and how about linking Gatwick and Stansted by Crossrail 3????. For those of us, who say we don't need any more capacity, such links are important.


Well as a non-expert, it sounds clever to me! At least for the terminals. You need to get some professionals to give us their thoughts. I'm curious now...


I like the idea of the taxiways, terminals and all that being underground (and I'm surprised no one has come up with this idea yet!), but an underground runway is not even worth considering. There just wouldn't be enough space to manoeuvre aircraft in a tunnel at high speeds. Also, the runway tunnel would have to be really damn large: as well as being at least 3.5 km long, it would possibly have to be even up to 100 metres wide and 45 metres high! In addition, overshooting the runway during landing would have far more devastating consequences (assuming the ends of the runway are also underground, just with apertures) since the plane would hit a wall instead of running over mud or grass, or hitting a fence. Not to mention that crosswind landing would be pretty much impossible...