Heathrow has told the government that the previous 2035 target for opening a third runway is no longer achievable, with the airport’s existing planning assumptions now pointing towards 2039.
The airport continues to target planning permission by 2029 and has maintained that construction of the runway could be completed within a decade of consent. On that basis, the outer edge of the current programme moves four years beyond the earlier 2035 ambition.
A Heathrow spokesperson said: “It’s right that ambitious targets were set; the sooner expansion begins, the sooner the whole UK will benefit. Our focus has always been to secure planning permission by 2029.
“Once achieved, the runway will be open within a decade – and the benefits of expansion can be felt from today. At least 108,000 new jobs and billions invested in supply chains in every part of the country.”
The change does not represent a new planning permission or construction commitment. Heathrow remains in the pre-application stage of the Development Consent Order process and approved investment in January to begin preparing its planning application.
The government has also been updating the policy framework against which any application would be judged. The Airports National Policy Statement sets the strategic planning basis for expansion, but designation of the policy does not itself authorise construction.
Heathrow would still have to submit a Development Consent Order application, undergo detailed examination, and secure a final decision before major construction could proceed.
The programme extends considerably beyond laying a new runway. Heathrow’s proposal includes additional terminal capacity, surface-access changes, and substantial engineering around the M25. The airport has previously estimated the runway itself at £21bn within a wider £49bn expansion and modernisation programme.
Heathrow says expansion would be privately financed and could eventually increase capacity to as many as 150m passengers a year and up to 756,000 annual flights. Its economic case centres on additional routes, greater competition between airlines, increased cargo capacity, and stronger international connectivity.
The investment case depends partly on regulation. Airlines and airport investors need clarity on how early development and construction costs would be recovered, while the Civil Aviation Authority’s approach to charges will influence the returns available on private capital.
Heathrow said in January that decisions on regulation and policy during 2026 would determine whether the programme could move into its next phase. Its shareholders support expansion, but the airport has repeatedly linked delivery to an acceptable framework for financing the project.
Environmental constraints remain another major part of the planning assessment. Aviation is difficult to decarbonise at the pace achieved in sectors such as electricity generation, leaving future emissions reductions dependent on more efficient aircraft, sustainable aviation fuel, airspace improvements, and developing technologies.
Expansion supporters argue that additional capacity can increase trade, tourism, investment, and the range of direct connections available from the UK’s main hub airport. Critics question whether additional flights can be reconciled with climate targets and whether projected economic benefits justify the environmental and local impacts.
The planning process will have to assess those competing considerations rather than assuming either the economic or environmental case in advance.
A Department for Transport spokesperson said: “There is currently no live planning application for a third runway, and we cannot comment on ongoing consultation processes or prejudice them in a way that will only delay progress.
“The timeline has always been ambitious. We’ll continue to work with promoters, including Heathrow, and all other stakeholders at pace to ensure the right framework is in place for which a planning application for a third runway could be considered.”
The extended timetable also affects businesses that could participate in the project. Major infrastructure programmes require engineering, construction, logistics, technology, materials, and professional-services capacity over many years. Suppliers are more likely to recruit specialist workers and invest in equipment when procurement schedules are sufficiently clear.
Delays can therefore shift expenditure as well as opening dates. Some preparatory, planning, and design work takes place years before construction, but the heaviest demand across the supply chain depends on consent, financing, and defined construction packages.
The immediate milestone remains the attempt to secure planning permission by 2029. Meeting that target would preserve a route towards an operational runway by 2039 under Heathrow’s stated ten-year construction assumption. Further slippage in policy, planning, financing, or construction would put even that timetable under pressure.
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