The UK House of Commons has voted to approve a staggering sum of 16 billion pounds for the extension of Heathrow airport. This is more expensive than projects of a much larger scale, such as the Gotthard Base Tunnel or the Brandeburg airport in Berlin.

Why is it so expensive to add a single runway to an existing airport?

  • Your question seems to misstate the facts. First, the UK treasury is not paying for the expansion, so I suspect that the approval was not of the cost, but of something else. I haven't been able to find the details online, however. Second, the question equates the approved project with "adding a single runway to an existing airport" but as I understand it the project comprises much more than simply adding a runway; there is also a need for new terminal construction and improvements to transportation and other infrastructure. I do not know whether these are included in the current approval.
    – phoog
    Jun 26 '18 at 15:49
  • @phoog still, 16 billion pounds is an insane amount of money even if you're building a brand new airport. Jun 26 '18 at 15:51
  • 2
    +1 I think that even though a private company is supposedly funding it, this question relates to politics because it was approved by Parliament specifically at this high amount.
    – Eremi
    Jun 26 '18 at 15:52
  • @Eremi it's certainly a political question; I don't mean to imply that it isn't. JonathanReez I agree that the high cost deserves explanation. My point is that getting the facts straight will probably take you much closer to the answer than you are at this point, and I suspect that it may help identify more interesting aspects of the plan to call into question. The more of that you can do in your question, the less work your answerers will have to do.
    – phoog
    Jun 26 '18 at 15:58

It is not just a new runway, but also an entirely new terminal and the infrastructure to support it, purchasing the necessary land around the expansion, putting a very busy road underground, and various environmental concerns.

This business jargon filled report from 2014 by Heathrow outlines the proposal, and after skipping past the normal buzzwords you can see their rough cost estimates on page 44:

  • £11.1 billion for:

    Airport infrastructure

    Includes runway, taxiway, apron, aircraft stand, terminal capacity and pier, tracked transit, baggage system, access road, car park and control tower costs

  • £0.9 billion for:

    Surface access

    Includes road, highway, motorway, and rail costs

  • And £3.6 billion for:


    Includes reprovision of wildlife habitat and flood mitigation


    Includes residential property, commercial property, and general land compulsory purchase, community facilities re-provision, community infrastructure levy, and air noise compensation costs

Although the report is from May 2014, the total of these costs comes to £15.6 billion. That's roughly what the current budget for the expansion is, so this plan is likely close to how the money will be spent.


There is a good summary by the FT here. To paraphrase. It is expensive because it suits Heathrow Airport Holdings (formerly BAA) to make it expensive as they can get cheap finance for it. If they were to squeeze costs they would not be able to get so much money.

A couple of other things to note:

I had thought the cost of the land would be a major factor but this looks to be merely about £350 Million

The costs of diverting the M25, one of Europes busiest roads and putting the runway over it are substantial and not separately accounted for.

  • 1
    What is BAA? Article is behind paywall.
    – Alex
    Jun 26 '18 at 17:12
  • Apologies, it is now called Heathrow Airport Holdings Jun 26 '18 at 17:44
  • 1
    Downvoted because of paywalled article as source. Post the relevant passage(s) from the article here, with attribution.
    – Ian Kemp
    Jun 26 '18 at 18:19
  • @IanKemp Ah, sorry it was a free article when accessed from google but not when linked. Jun 27 '18 at 8:23

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