Heathrow has been told to address concerns raised by the national aviation watchdog over its expansion plan 'decisively and urgently'.
A letter from the chief executive of the Civil Aviation Authority (CAA), Richard Moriarty, to the Department for Transport raised concerns over the 'need to provide high quality information about the costs of the scheme... and the need for [Heathrow] to provide assurance that its revised timetable is realistic'.
After the airport announced that it now expects to launch its statutory consultation in June 2019 rather than in the first quarter of 2019, the CAA called for immediate action to provide reassurance over the project's timing.
Heathrow must 'demonstrate to stakeholders that its new timetable is realistic, achievable and allows sufficient time for high quality engagement while ensuring timely delivery' the letter said.
The airport has also recieved numerous requests for more information on costs and efficiencies that could provide evidence it will keep airline charges under control. However it is yet to respond in with sufficient information.
A Heathrow spokesman said: 'We continue to engage with all stakeholders on our expansion plan and look forward to presenting a detailed preferred masterplan for further public consultation next year. We remain on track to submit a planning application in 2020 and the new runway to open in 2026.'