Airport congestion could cost more than £5bn a year by 2015 if plans to expand London's airports are shelved, a study has found.
British Airways is Heathrow airport's largest customer
The Oxford Economic Forecasting study said UK airport congestion cost £1.7bn in 2005.
Proposed airport expansion would boost the UK economy by £13bn a year, outweighing the costs of climate impacts by 2030, the study found.
Aviation groups, airlines and airport operator BAA carried out the study.
The groups are fighting against increasing pressure to shelve expansion plans at major London airports and reduce aviation emissions, in the wake of environmental concerns.
The British government has supported plans for a third Heathrow runway after 2015 and a new runway at Stansted by 2012.
Third Heathrow runway
The study showed that a third Heathrow runway could add £7bn to the UK economy by 2030.
However, expansion plans are strongly opposed by environmental groups and local residents.
Airport operator BAA said Heathrow would lose competitiveness to Paris, Frankfurt and Amsterdam if it did not expand.
The study follows last week's release of the former British Airways (BA) chief Rod Eddington's report, which recommends a nationwide system of road pricing.
Current BA boss Willie Walsh said opposition to the expansion at Heathrow was "short-sighted" and called on the government not to tax airlines.
"There is no evidence that additional taxation will do anything to improve the environmental performance of aviation," he said.