The speech made by Sarah Olney, the Liberal Democrat MP for Richmond Park, in the House of Commons on 14 May 2026.
The debate surrounding a third runway at Heathrow has stretched over the past three decades. The Liberal Democrats have long stood by communities who oppose a third runway, arguing that the economic benefits are overstated and the environmental consequences are unavoidable. Although I have always opposed a third runway at Heathrow, the current proposal could not have come at a worse time. The cost of expansion has doubled over the past 10 years, and the addition of nearly 300,000 more flights, which expansion implies, will make our net zero targets almost unachievable.
It is widely rumoured that even Heathrow Airport Ltd did not believe the timing of expansion to be practical. Despite that, on 29 January 2025, the Chancellor announced her support for a third runway to be built at Heathrow airport. This endorsement was the landmark announcement during her speech on growth; as such, it has a significant amount of political weight behind it. My plea to the Minister is that any decision taken on a third runway at Heathrow should be based on merit and unbiased data, not politics. The decision has an enormous impact on millions of lives, and it must be more than just a signal to investors to compensate for the Government’s economic mismanagement.
The Chancellor believes that expansion at Heathrow will produce economic growth. Nearly 18 months later, however, the Government have yet to produce their economic analysis to support that assertion, and the figures raised in the Chancellor’s speech on growth were drawn directly from an internal business case prepared for Heathrow airport and have not been independently verified.
The Department for Transport’s own updated appraisal report from 2017 shows that the net present value of a third runway ranges from just £3.3 billion to minus £2.2 billion. Now it has been admitted that even that figure is a generous estimate, as the DFT’s guidance suggests that international transfer passengers, who are estimated to make up 75% of a projected third runway’s capacity, do not contribute to the UK’s economy. When discounting those passengers, it is estimated that the net present value could be reduced by as much as a further £5.5 billion.
In addition, the New Economics Foundation asserts that twice as many people fly out of the UK than fly in, thus exporting more money out of our economy. An assessment of the impacts of inbound and outbound tourism flows is currently missing from the economic analysis of aviation’s contribution to the economy. Will the Minister provide reassurance that that research will be conducted and published with the airports national policy statement?
Heathrow Airport Ltd has cited that the cost of building a third runway will be an eyewatering £49 billion, before factoring in an estimated £100 billion in carbon abatement costs and at least £15 billion of investment on surface access upgrade improvements. Without that upgrade, there will be no way to deliver sufficient passengers to Heathrow to utilise the additional capacity and deliver the supposed economic benefits.
The Government have said that funding for a third runway at Heathrow will be privately financed. With Heathrow already drowning in over £15 billion-worth of debt, I am not convinced. I would therefore like to ask again, will the Minister provide reassurances that none of the costs associated with building a third runway at Heathrow will be pushed on to the taxpayer?
Danny Beales (Uxbridge and South Ruislip) (Lab)
I thank the hon. Member for securing this important debate on an issue that matters to my constituents in Hillingdon, to her constituents and to many constituents across the west London area. As she rightly points out, there have been discussions about the third runway being privately financed, but as she has touched on, there are public sector burdens and costs too, including from the extra pressure on the Elizabeth line, because of the capacity that will be needed, and on the local road network. Does she agree that it is vital when looking at the economic case that possible public sector pressures are fully accounted for in the decision-making process? Does she agree that the Government’s four tests are absolutely vital, and that we need transparency about how those tests will be measured and assessed?
Sarah Olney
The hon. Gentleman is absolutely right that we need to see the economic case and to look at it in the round—not just the specific costs associated with building the runway, but all the additional costs associated with operating it at capacity and all the impacts that that will have on Heathrow, along with the whole of London and the south-east.
The economic argument simply does not stand up to scrutiny, while the social and environmental consequences of a third runway are unavoidable. Communities would be severely impacted by the additional flights that a third runway would bring. It is expected that nearly 325,000 more people will fall within the Department for Transport’s “significantly affected” decibel level measurement. That does not even reference the increased bombardment of noise that houses already impacted by Heathrow’s flights are likely to experience. Not only would that noise disturbance affect people’s everyday lives, whether their sleeping pattern or their ability to work from home, it would have serious physical and mental health repercussions for local residents.
People living in communities surrounding Heathrow have a 24% higher chance of stroke, a 21% higher chance of heart disease and a 14% higher chance of cardiovascular disease compared with people exposed to low levels of aircraft noise. Will the Minister confirm how many people will be exposed to noise at 45 decibels, the level that the World Health Organisation estimates that health impacts begin? Will the Government commit to setting a minimum acceptable level of noise by which any expansion proposal can be judged? Will the Government also commit to ensuring that there is no increase in night flights? People deserve a full night of undisrupted sleep, and I would be grateful if the Minister could confirm that the Government do not plan to approve anything that would mean more planes fly over households during night hours.
Yesterday, the Government outlined their plan to introduce the civil aviation Bill in this parliamentary Session. Will the Minister outline a timeline for the introduction of that Bill, and will he explain how the Government can provide communities with reassurances that a third runway will not bring new or extended disruptions when airspace changes are yet even to be drawn up?
On the environmental argument, it should almost go without saying that adding nearly 300,000 extra flights to our skies each year will have a profound impact on air pollution and climate change. This Government have used wishful thinking in their assertions that sustainable aviation fuel will mitigate the additional pollution from Heathrow expansion. They are yet to provide any evidence that shows how Heathrow can expand while complying with their legal air pollution limits.
International uncertainty over China’s introduction of their SAF mandate, which accounts for more than 90% of our imported SAF, and challenges to UK-US trade have meant that the UK’s SAF targets, which in themselves would not mitigate pollution from Heathrow expansion, are even more difficult to deliver. The challenges to the UK’s ability to produce and import SAF were underscored by the Climate Change Committee’s report last year, which estimated that only 17% of the UK’s aviation industry will use SAF by 2040. That is 5% lower than the Government’s mandated targets and 8% below the EU’s target. The estimate does not even take into account the additional flights that would come in and out of the UK as a result of the proposed airport expansion.
Heathrow is already the single biggest source of carbon emissions in the UK, and expansion will add an extra 8 megatonnes to 9 megatonnes of CO2 every year. The Climate Change Committee’s balanced pathway to net zero estimates that aviation will contribute 23 megatonnes of CO2 by 2050. A third runway at Heathrow would increase emissions at the airport alone to 20 megatonnes. Does the Minister still believe that the UK can be compliant with our net zero targets with the expansion of Heathrow airport?
This Government have repeated that they will honour and respect the Labour party’s four tests, as highlighted by the hon. Member for Uxbridge and South Ruislip (Danny Beales). They are: growth across the country, noise issues to be addressed, air quality to be protected and our climate change objectives to be met. They must be passed before expansion can be approved. As I have just laid out, I do not believe that any of those tests can be passed, let alone all four, but I ask that the Government honour the principle of the tests and do not attempt to circumvent them by using biased data.
I hope I have underlined the importance of this decision for our economy, environment and local communities. Moreover, I hope that this speech has impressed on the Government that this decision cannot move ahead solely on the basis of political expediency.
