Thursday's scheduled Cabinet sign-off on plans for South East airport expansion faces delays – possibly into the new year.
The possibility follows the publication by the London Evening Standard of allegations of a 'cover-up', in the final report of the Airports Commission, which backed a third runway at Heathrow, of increased risks of plane crashes at the west London airport.
The Commission's report included the results of research by the Health and Safety Laboratory (HSL), stating that the 'background rate' of crashes would be virtually unchanged if the new runway were built. But the HSL went on to conclude that the likelihood of a crash on take off or landing could rise by as much as 60% at Heathrow (compared with a possible doubling as the result of building second runway at Gatwick).
There are also allegations that the Commission requested the replacement of the term 'crash risk' by 'ground risk'.
The Commission has now closed down and is reported to be shredding its documents. The press office at Heathrow's main rival, Gatwick, declined to comment on the allegations.
The Government has a ready-made excuse for delaying its final decision until after the May 2016 London mayoral election, on the grounds that air pollution issues have not been adequately dealt with, to satisfy the concerns of MPs for constituencies lying close to Heathrow, and that further research is needed.
Tory mayoral candidate Zac Goldsmith MP, who represents Richmond Park, under the flight path, has said that he could reconsider public threats to resign if the government asks both airports to 'prove that their plans can be reconciled with legal air quality commitments'.