MPs Question Whether Heathrow’s £49bn Third Runway Can Be Fully Privately Funded

Questions are mounting over how Heathrow Airport plans to finance its proposed third runway, with MPs warning that taxpayers could ultimately face some of the financial burden despite government assurances of private investment.

The airport’s expansion scheme is expected to cost around £49 billion, making it one of the most expensive infrastructure proposals currently under consideration in the UK. Alongside construction costs, critics argue billions more could be required for environmental measures and major transport upgrades needed to support increased passenger numbers.

During a parliamentary discussion on the project, several MPs challenged the claim that the development would rely solely on private funding.

Sarah Olney, MP for Richmond Park, pointed to Heathrow’s existing debt levels as a major concern. She argued that the airport is already carrying liabilities exceeding £15 billion while also facing substantial future costs linked to emissions reduction and improvements to surrounding transport infrastructure.

According to Olney, rail and road networks around Heathrow would need significant investment if the airport is to handle the additional traffic generated by an expanded runway operation. She questioned whether such extensive infrastructure improvements could realistically happen without public financial involvement.

Heathrow formally approved funding earlier this year to begin progressing its planning application for the runway scheme. The airport says expansion would allow passenger numbers to rise to as many as 150 million annually and increase flight capacity to roughly 756,000 flights each year.

The Government continues to support the proposal and intends to revise national aviation planning policy to accommodate the expansion.

However, concerns extend beyond the airport itself. Uxbridge and South Ruislip MP Danny Beales warned that increased demand on public infrastructure would inevitably create costs for government and local authorities.

He highlighted the likely pressure on services such as the Elizabeth Line and local road systems, arguing that the surrounding transport network would require major upgrades to cope with additional airport traffic.

The scheme also includes a significant engineering challenge involving the diversion of part of the M25 motorway to make room for the proposed runway. Heathrow has previously maintained that the motorway alterations can be completed while keeping the route operational.

Further criticism came from Twickenham MP Munira Wilson, who compared Heathrow’s financial situation to that of Thames Water, suggesting both organisations are attempting to manage large-scale infrastructure investment while carrying substantial debt.

Wilson warned that if the project encounters financial difficulties, passengers and taxpayers could eventually bear the consequences through higher travel costs or government intervention. She argued that airlines have already raised concerns about rising airport charges being passed on to customers.

Despite the criticism, ministers insist the expansion will not rely on public money. Transport minister Keir Mather told Parliament that Heathrow’s runway proposal remains a privately financed project and said the Government’s position on taxpayer funding has not changed.

Mather also stated that the Civil Aviation Authority would continue monitoring costs to help ensure passengers are protected from excessive price increases during the expansion process.