Members of the UK climate-change panel are insisting that today's report on air transport growth is not an endorsement of expansion at London Heathrow.
The independent Committee on Climate Change has concluded that passenger demand must be limited to a 60% rise on 2005 figures if the UK Government is to meet 2050 carbon targets.
It highlights the effect on demand that could be achieved if expansion is limited to London Heathrow, London Stansted and Edinburgh.
But the report stresses: "There are no clear implications of our analysis for specific airports."
A spokeswoman for the committee adds that that panel has simply shown the extent to which air travel demand must be restricted, and that it is not responsible for deciding how the Government should proceed with optimising capacity.
"We're agnostic as to where the airports are based," she says.
In its report the Committee on Climate Change says that, at the current rate of technological progress, air traffic movements will have to be limited to 3.4 million per year by 2050, a rise of 55% on 2005.