Passengers will consume at least 1,600 meals in plastic containers, but each plane traveling to London will guzzle more than 200 tons of jet fuel and pump out more than 500 tons of carbon dioxide, as well as other greenhouse gases.

"Beneath the glamorous high-flying image of aviation is a grossly polluting industry," said Paul de Zylva, head of Friends of the Earth in London.

Environmentalists say airlines rate as one of the most polluting forms of transport, with 16,000 commercial jets producing over 600 million tons of carbon dioxide every year.

Climate change, caused by greenhouse gases such as carbon dioxide, is deemed by many experts to be the biggest long-term threat to mankind. They predict rapidly rising temperatures prompting higher sea levels, devastating floods and droughts.

The United Nations Intergovernmental Panel on Climate Change estimates aviation causes 3.5 percent of man-made global warming and that figure could rise to 15 percent by 2050.

NASA scientists say condensation trails from jet exhausts create cirrus clouds that may trap heat rising from the Earth's surface. This could account for nearly all the warming over the United States between 1975 and 1994.

And air travel is booming.

The International Air Transport Association (IATA), the body which represents the world's airlines, accepts that aircraft cause environmental damage.

"Every minute we can save in flight times has a positive impact on the environment and on our costs," said IATA spokesman Anthony Concil.

NO GREEN AVIATION RULES

Despite the industry's heavy environmental toll, guidelines on international aircraft emissions were excluded from the Kyoto protocol on climate change and aviation fuel is tax exempt.

Aerospace firms have made huge leaps forward, with commercial jets now 70 percent more fuel efficient per passenger mile than they were 40 years ago, thanks to better engines, lighter materials and aerodynamic designs.

And cost-obsessed carriers are continuously searching for ways to use capacity better, find more direct flight paths and cut congestion in order to trim the hefty fuel bills which make up 25 percent of airline operating costs.

Most discount airlines have young, more fuel-efficient fleets and newer airlines in regions such as Asia have leap-frogged older technologies to buy new planes.

Dirt cheap airfares due to the runaway success of low-cost carriers mean thousands more people are now taking to the skies for short hops around Europe or the United States, and air travel is set to rocket in the fast-growing economies of Asia.

"It's a Catch-22 situation. Many developing countries want to promote tourism as a revenue source and a lot of no-frills airlines are appearing in Malaysia and other parts of Asia," said Gurmit Singh, executive director of Malaysia's Center of Environment Technology and Development.

"It's one of the unsustainable forms of development that Asian countries are rushing into," Singh said.

The sheer growth of passenger volumes is likely to negate the benefits of future improvements, say environmentalists.

Simon Thomas, chairman of London-based environmental consultancy Trucost, estimates that technological improvements help trim emissions by around 1 percent a year, a drop in the ocean when the aviation industry is forecasting 5 percent annual traffic growth for the next two decades.

"That's an enormous difference. It has the ability to completely undermine the Kyoto protocol," said Thomas.

OPTIONS OPEN

Links between aviation and climate change have attracted widespread attention in Europe where environmental groups are calling for measures to curb the impact of airline emissions.