Heathrow Airport’s proposal to build a third runway faces significant delays and logistical challenges that could push the project’s completion to 2040, according to a report by the American construction firm Bechtel. The 3,500-metre runway is part of a £49 billion project aimed at nearly doubling the airport’s capacity by 2035, but the report suggests this timeline is unrealistic.

Bechtel, which has experience in numerous international airport expansions, reviewed Heathrow’s plans and determined that preparatory work alone would not be finished until 2036, at the earliest. This assessment comes despite government backing for the project, which has yet to receive formal planning approval. Over recent weeks, the report has been shared with officials at the Civil Aviation Authority, the Treasury, and the Department for Transport.

Key challenges identified by the report include the relocation of essential infrastructure and natural features that lie in the path of the proposed runway. Among these are seven significant assets such as rivers, lakes, a substation, a railway, and an energy waste plant. Notably, several angling lakes—including Old Slade Lake, Orlitts Lake, and Colnbrook West Lake—would need to be moved. Old Slade Lake, a 50-acre former gravel pit, is recognized for its large populations of carp, bream, and tench. Any modifications to these water bodies require approval from the Environment Agency and would necessitate larger replacements paired with comprehensive flood management strategies.

Another substantial hurdle involves the Longford substation and its associated high-voltage overhead cables. Bechtel estimates the relocation of this infrastructure alone could take seven years, and no alternative site has yet been identified. Heathrow contends that relocating the substation may not be necessary due to its plans to acquire all properties within the nearby village. Additionally, the project would require diverting a portion of the M25 motorway, the busiest in the UK, to run beneath the new runway. Heathrow officials maintain that this can be achieved without significant disruption by constructing the new segment offline and switching traffic overnight.

In response to the difficulties outlined, billionaire hotelier Surinder Arora has proposed an alternative 2,400-metre runway designed to be operational by 2035. This compromise would avoid the need to move the M25 and reduce the scale of other enabling works. Arora cautioned that the full third runway project could become “the next HS2,” referencing the costly and delayed high-speed rail initiative.

Heathrow disputed Arora’s proposal, emphasizing that Arora has presented multiple plans over the past 18 months without sufficient detail and has no experience managing airport operations or construction. The airport reiterated that its privately funded plan is both comprehensive and deliverable. The Department for Transport indicated it would soon open consultations on any revisions to the original runway proposal.