A third runway at Heathrow is sold as growth for the whole country. The government's own appraisal puts that growth at up to 0.05 per cent of GDP a year, and the reviewer it paid to check the work says the claim about the regions can't be made from the modelling.
Crossbencher · 30 July 2026
Heathrow's third runway has one public justification, and it's growth. Strip away the talk of hub status and global Britain and what remains is a promise that building it makes the country richer, and that the country means all of it. The Department for Transport has now published the modelling behind that promise. The modelling doesn't say what the promise says.
Start with the headline number, because it's the department's own. The upper bound on the annual GDP effect, in the impact report published alongside the consultation, is 0.05 per cent. Not the boost to Heathrow, or to west London. To the United Kingdom, per year, from a 3,500-metre runway crossing the current line of the M25 at an estimated cost of £33 billion. The airport would go from 480,000 flights a year to as many as 756,000. For that, a twentieth of one per cent.
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