A report authored by Paul Mansell, an adviser to the Treasury on infrastructure projects, warned that the government backed expansion could face serious risks if it encounters delays and cost overruns similar to those experienced by HS2.
Heathrow has estimated that it can build a privately financed third runway and associated infrastructure for around £49 billion, with operations beginning by 2035. The airport says the project will be funded largely through increased airline landing charges.
However, the proposals have drawn strong opposition from airlines including British Airways owner International Airlines Group, as well as Virgin Atlantic, which argue that passenger costs could rise significantly.
Mansell questioned whether Heathrow’s timetable, even if planning approval were secured by 2029, was realistic. He suggested that a six year delivery plan could amount to what he described as strategic misrepresentation, citing expert concerns about overly optimistic infrastructure forecasts.
The report also challenged Heathrow’s assertion that no taxpayer money would be used, describing it as a serious misunderstanding of wider value for money implications and consumer impact. Heathrow maintains that its timeline depends on external factors, including planning reforms.
Shared by Whitehall sources, the report criticised transparency issues, strained decision making, and a breakdown in trust between the airport and its airline partners. It warned against repeating failures seen in major public projects such as HS2, which has experienced repeated delays and significant cost escalation.
Mansell argued that if similar problems occur at Heathrow, confidence in UK infrastructure delivery could be damaged, with potential consequences for the aviation sector and construction industry.
To support the wider expansion programme, Heathrow has outlined capital expenditure plans of approximately £59 billion during its next regulatory period, including £10 billion over the next five years to maintain operations. The scale of spending represents a significant increase compared with current annual investment levels.
The report described the projected expenditure as substantial and suggested that, despite Heathrow’s claims, costs would ultimately be reflected in consumer charges.
Airlines also pointed to past project delays at the airport, including cost increases in the Terminal 2 baggage system upgrade and other infrastructure works that exceeded original budgets and timelines.
The report was commissioned by Heathrow Reimagined, a coalition of airlines and stakeholders advocating changes to the airport’s regulatory framework. It comes ahead of a key decision by the Civil Aviation Authority, which is reviewing the airport’s business model and cost recovery arrangements.
Proposals in the report include governance reforms aimed at strengthening accountability and ensuring airline input in investment decisions from the outset, with enhanced oversight.
A Heathrow spokesperson said the airport remains confident in its expansion plans, citing previous privately financed projects delivered on time and on budget, and expressed willingness to engage constructively with stakeholders.
A spokesperson for the Department for Transport said the expansion would attract investment, improve connectivity, and support jobs across the country. The department has launched a review of the Airports National Policy Statement as part of the planning process for the third runway.
