Heathrow third runway pushed back to 2039 as planning timetable stretches

Heathrow Airport's proposed third runway is now expected to open in 2039, four years later than the previously stated 2035 target, as the airport works through the planning and regulatory process for one of the UK's largest infrastructure programmes.

Heathrow continues to target planning permission by 2029, with the airport maintaining that opening a runway within a decade of consent has always been its core scenario. Heathrow has described the earlier 2035 date as an ambitious target that would have required significant changes to regulations and policy. 

There is currently no live planning application for the runway. Heathrow is preparing its Development Consent Order application, with an eight-week public consultation on the expansion proposals scheduled from 27 October to 22 December 2026. The government's Heathrow Expansion National Policy Statement will provide the planning framework against which a future application would be assessed, but does not itself grant permission for construction. 

The wider Heathrow plan has been valued at around GBP49 billion and combines the third runway with major airport upgrades, new terminal capacity and extensive supporting infrastructure. Around GBP15 billion relates to upgrade works already planned, while approximately GBP33 billion covers the runway and associated expansion works, including modifications to the M25 motorway.

One of the project's most complex elements is the proposed realignment of the M25, which currently crosses the path of the future runway. Heathrow's proposals envisage shifting the motorway west and lowering it into a new section beneath the runway, requiring major highway, bridge, earthworks, drainage and utility construction while keeping one of Britain's busiest roads operational.

The airport itself is already operating close to capacity with two runways. Expansion would create additional aircraft movement capacity while requiring corresponding changes to terminals, taxiways, baggage systems, surface access and other airport infrastructure.

Heathrow describes the project as fully privately financed and estimates that expansion could support at least 108,000 jobs across construction, operations and the wider supply chain.

The planning framework must first progress through consultation and parliamentary scrutiny before Heathrow can secure development consent for its own scheme. A Development Consent Order application will then require detailed assessment of issues including noise, air quality, climate impacts, communities and economic effects.

If consent is achieved in 2029, Heathrow's current programme would allow roughly ten years for construction and commissioning before the third runway enters service in 2039.

For a scheme involving an operational international airport, a live motorway, major terminal infrastructure and extensive landside works, the four-year shift is less a change in the physical ambition of the project than a recognition of the time required to move a megaproject of this scale from planning into construction.