The Department for Transport is currently consulting on a draft National Policy Statement that would pave the way for a third runway at Heathrow. LADACAN has reviewed the detailed technical papers that sit behind that consultation – the cost-benefit analysis, the economic modelling, the aviation forecasts, the sustainability appraisal and the health impact assessment. What we found surprised us: the Government’s own evidence, read carefully, does not support the case for expansion. In several places it actively undermines it.
We’re publishing this because these documents are long, dense, and written for specialists. Most people will never read them. But the admissions buried inside them matter, and we think residents deserve to see them stated plainly.
The economic case does not add up on the Government’s own figures
The Department’s own cost-benefit appraisal produces a negative result in every single scenario it tests. Depending on the assumptions used, the net cost to the country ranges from £23 billion to £120 billion. The appraisal’s own executive summary states plainly that once the costs of environmental damage are properly counted, they outweigh the benefits.
The wider economic boost the scheme is supposed to deliver turns out to be tiny once you look past the headlines. The Government’s own modelling puts the GDP benefit at around 0.05% by the mid-2050s – a fraction of a percent, for a scheme costing tens of billions and decades of disruption. Most of even that modest benefit comes from the one-off spending on construction, not from any lasting boost to aviation activity itself.
The promised jobs benefit is similarly weak. The Government’s own economic model assumes the country reaches full employment regardless of whether the runway is built, which means, in the model’s own terms, any employment increase from the scheme is transient rather than permanent. The same modelling also confirms something LADACAN has argued for years: in the years immediately after a new runway opens, growth in passengers at Heathrow comes mostly from displacing passengers who would otherwise have flown from other UK airports, not from genuinely new demand.
The tourism deficit the Government doesn’t talk about
One of LADACAN’s long-standing arguments is that the economic case for aviation growth ignores a basic fact: UK residents flying abroad on holiday spend far more overseas than foreign visitors spend here. That’s not a spurious claim – it’s in the Government’s own statistics. Official figures show UK residents spent £78.6 billion travelling abroad in 2024, against £32.5 billion spent in the UK by overseas visitors – a tourism trade deficit of around £46 billion in a single year. That gap alone accounts for roughly three-quarters of the UK’s entire current account deficit for 2024. Heathrow, as the country’s dominant hub, is the primary gateway for that outbound spending. Growing the airport on the promise of economic benefit, when its dominant effect on the nation’s finances runs the other way, is a case that has simply note been properly made or evidenced.
The climate case rests on fuel that doesn’t exist yet, at a price nobody can afford
The Government’s own forecasts show that its net zero pathway for aviation has actually got harder to achieve since its last strategy, not easier. Projected emissions in 2050 are now higher than they were in the 2022 Jet Zero Strategy, because the Department has quietly reduced how much it expects sustainable aviation fuel (SAF) to contribute – down from 50% of the fuel mix to 30%.
Even that reduced figure looks optimistic. On the Government’s own numbers, SAF only reaches 17% of the fuel mix by 2040, and stays flat after that – meaning the great majority of jet fuel burned in 2050 is still expected to be ordinary fossil kerosene. SAF is also roughly two and a half to three times more expensive than kerosene, and that gap is not expected to close.
The carbon price used to justify the proposed scheme is, by the Department’s own admission, already out of date and too low – its own more recent forecasts show carbon prices running significantly higher than the figures used in this consultation. The price used is also only around a third of the Government’s own official valuation of the true cost of carbon to society. When the Department tested what would happen if carbon were priced at its full value, passenger demand growth fell sharply – suggesting the whole “need” case is built on carbon being priced artificially cheaply.
The noise case is built on flight paths that don’t exist yet
This is perhaps the most striking gap of all, and it matters directly to communities under flight paths from every London-area airport, not just Heathrow.
The noise assessment behind this consultation uses old, indicative flight paths dating from a 2015 study, because the real airspace redesign hasn’t happened yet – that job now belongs to a new national body, the UK Airspace Design Service (UKADS), which has barely started its work in the areas that matter most. The Department admits, in its own words, that the real flight paths eventually used “may be different from those that informed the noise assessment” behind this very consultation. In other words, the Government is asking to be trusted on noise using a noise assessment it already knows may turn out to be wrong.
Nowhere in the entire policy document is there any assessment of how a bigger Heathrow would affect the airspace available to other airports nearby. This is exactly the kind of conflict LADACAN has raised for years in relation to Luton: departing aircraft from Luton are already held down low, unable to climb continuously, because of conflicts with Heathrow traffic. A third runway at Heathrow, designed without any visible consideration of these knock-on effects, risks making that worse – for Luton and for other airports sharing the same crowded skies over south-east England.
Communities are being shut out of the process that will decide this
It isn’t only the evidence that concerns us – it’s who gets a say in it. Community representation was promised a seat on the board overseeing the new national airspace design process. That promise has since been quietly dropped: recent proposals suggest only airlines and airports will be represented, with communities left out entirely. As members of the Government’s own Airspace and Noise Engagement Group, LADACAN has formally objected to this. It fits a wider pattern: as the decisions that most affect people living under flight paths move into more technical, less visible bodies, the opportunities for the public to be heard are shrinking rather than growing.
Our conclusion
LADACAN is not opposed to aviation, and we are not calling for airports to close. Our position is pragmatic and responsible: no new runway capacity is needed. Existing runway capacity should be used more responsibly, and demand should be actively managed – for example through a frequent flyer levy – rather than expanded indefinitely. Having gone through the Government’s own evidence in detail, we don’t think a credible case for a third runway at Heathrow currently exists. We’ve said so, in full, in our formal response to this consultation.