London Heathrow Airport has warned that its long-planned third runway could be delayed by four years, pushing its potential opening from 2035 to 2039 as the project faces a lengthy planning and regulatory process.
The UK government had aimed for the new runway to become operational by 2035, a target initially set under former Chancellor Rachel Reeves when the government backed Heathrow expansion in January 2025. However, the airport now considers that timetable increasingly difficult to achieve without changes to the planning process.
“Our focus has always been to secure planning permission by 2029. Once achieved, the runway will be open within a decade,” a Heathrow spokesperson told Reuters.
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The Department for Transport acknowledged that the 2035 timetable had “always been ambitious”, while saying it would continue working with Heathrow and other stakeholders to establish the framework under which a planning application could be considered. According to DfT spokesperson, there is currently no live planning application for the runway.
A draft planning framework for Heathrow expansion was published for consultation in June 2026. Once finalised, it will need to go before Parliament, while Heathrow must still submit a formal development consent application before construction can begin.
The proposed third runway forms part of a wider £49 billion (around €56 billion) investment programme at Heathrow. Current estimates put the runway project itself at around £33 billion (€38.5 billion), alongside upgrades to terminals and other airport infrastructure.
The expansion would significantly increase capacity at the airport, which currently handles more than 80 million passengers annually using two runways and four passenger terminals. Heathrow’s plans could increase annual aircraft movements from the current cap of 480,000 to more than 700,000, while requiring major infrastructure works, including rerouting part of the M25 motorway.
Planning the project has itself become increasingly expensive. Previous estimates showed that costs associated with preparing the third runway application could exceed £1 billion, with Heathrow seeking to recover some expansion-related expenditure through higher passenger charges.
Supporters argue that additional capacity would strengthen the UK’s international connectivity and generate jobs and investment. Heathrow says expansion would create at least 108,000 new jobs and bring billions of pounds into supply chains across the country.
However, the project continues to face opposition over noise, air pollution, carbon emissions and its impact on communities surrounding the airport. London Mayor Sadiq Khan remains opposed to the expansion, while the UK’s climate advisers have said a third runway should only proceed alongside measures addressing the additional emissions generated by increased aviation.
The potential delay adds another chapter to a project that has been debated for more than two decades, with Heathrow now working towards planning approval by 2029 and a possible opening by 2039.
