Airlines have long questioned where the money for the runway will come from, expressing concern that Heathrow will raise airport charges.
Earlier this year, the airport cut charges for domestic flights, but has so far not been entirely forthcoming on how it will pay for the estimated £14 billion upgrade.
Transport secretary Chris Grayling asked the CAA to advise the DfT on how well Heathrow is engaging with and responding to the airline community on its plans for delivering extra capacity. In 2016, Grayling set out his vision for doing so without raising airport charges.
In his letter to Caroline Low at the Airport Capacity Directorate, CEO Richard Moriarty said the CAA ‘fully appreciates’ that the plan is still in development “so some uncertainty is inevitable” and acknowledged that Heathrow has “committed to enhance its cost estimates”.
However, he said the airport has further steps to take ‘to secure airline confidence’.
Moriarty said: “Unless there is a significant improvement in this area we will consider whether there are further steps we should take to support the proper discharge of our statutory duties.”
Moriarty hinted that this could include making a formal information request under section 50 of the Civil Aviation Act 2012, as well as “additional licence obligations” requiring Heathrow to provide more detailed information.
Following Heathrow’s announcement that it would delay its statutory consultation to June 2019 rather than the first quarter of the year, the CAA is also calling on the airport to assure stakeholders that its new timeline is realistic and achievable.
Responding to the release of the letter on the CAA’s website, a Heathrow spokesperson said: “We continue to engage with all of our stakeholders on our expansion plans 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 for the new runway to open in 2026.”
The CAA will report to the DfT again in early 2019 on how Heathrow’s plan has progressed.
Heathrow's expansion is already set to face a judicial review in March 2019 after campaign groups raised concerns over the third runway's impact on the environment and local communities.
The Arora Group, which owns a large portion of the land around Heathrow, submitted its own plan for expansion, which it says could be cheaper than the airport’s option.