Heathrow will pay for the cost of the new runway ? about ?17bn ? but the bulk of the cost of the road and rail infrastructure could end up being paid by the taxpayer. Estimates of the cost of that road and rail infrastructure vary considerably. The Airports Commission put it at ?5-?6bn.

The expansion of Heathrow Airport, including the controversial third runway project, is primarily funded by Heathrow Airport Limited (HAL), a private company. HAL is owned by a consortium of international investors, including the Qatar Investment Authority, China Investment Corporation, and the Spanish company Ferrovial. The funding comes from a combination of private equity, multi-billion-pound loans from international banks, and the airport's own significant revenue streams from airlines and passengers. While the UK government has voiced support for the project (most recently confirmed by the Labour government in 2025), it has explicitly stated that no taxpayer money will be used for the construction. Instead, the costs will likely be recouped through "airport charges" levied on the airlines that use the new facilities, which can sometimes lead to higher ticket prices for travelers in the long run.

The expansion of Heathrow Airport, particularly the construction of a third runway, is primarily funded through a combination of private investment and passenger fees. Heathrow Airport Holdings, the private company that owns and operates Heathrow, is responsible for financing the majority of the project. This funding is expected to come from a mix of sources:

1. Private Investment: Heathrow Airport Holdings and its shareholders will provide significant capital for the expansion. This includes contributions from institutional investors and other stakeholders.

2. Passenger Charges: A portion of the funding will come from increased passenger fees. These charges are levied on airlines, which may pass the costs on to passengers through ticket prices.

3. Debt Financing: Heathrow is likely to raise additional funds through borrowing, including issuing bonds or securing loans from financial institutions.

4. Government Support: While the UK government supports the expansion as part of national infrastructure development, direct public funding for the project is limited. However, the government may provide indirect support, such as guaranteeing loans or facilitating planning permissions.

The exact financial structure and contributions may evolve as the project progresses and final agreements are made. The goal is to ensure that the expansion is financially sustainable while minimizing the burden on taxpayers.