But few of the 400 passengers crammed on to each jumbo jet taking off over Botany Bay ever consider the environmental impact of their 17,000km intercontinental trip.


Passengers will consume at least 1600 meals in plastic containers, but each plane travelling to London will guzzle more than 200 tonnes of jet fuel and pump out more than 500 tonnes 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.


Scientists say jet emissions lead
to environmental damage

Environmentalists say airlines rate as one of the most polluting forms of transport, with 16,000 commercial jets producing over 600 million tonnes 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 humanity.


They predict rapidly rising temperatures prompting higher sea levels, devastating floods and droughts.


The UN Intergovernmental Panel on Climate Change estimates aviation causes 3.5% of man-made global warming and that figure could rise to 15% 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.


Environmental impact


And air travel is booming.


Commercial jets now 70% more fuel efficient per passenger mile than they were 40 years ago, thanks to better engines, lighter materials and aerodynamic designs

The International Air Transport Association (IATA), the body that 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. 


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% 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% 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.


Low-cost carriers


Established airlines are being
challenged by low cost carriers

Very 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 Centre 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% a year, a drop in the ocean when the aviation industry is forecasting 5% 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.


Curb emissions


China's air passenger numbers
will reach 215 million by 2014

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.


Environmental taxes, airline emissions trading or increased

investment in high-speed rail networks are the most commonly touted methods to wean passengers from air travel.


But in North America, which makes up 40% of world air travel, the issue has yet to make a big public impact and the environment remains low on the agenda in developing countries as they race for economic growth.


Air travel in China alone, which has the largest number of

domestic and international scheduled passengers in the Asia-Pacific region, is forecast to leap over 200% from nearly 67 million in 1999 to around 215 million in 2014.


The aviation industry opposes any new green taxes, saying many airlines are still in recovery mode. The world's carriers lost some $30 billion in the years since the 11 September 2001 attacks on the United States.


The world's carriers lost about $30 billion in the years since the 11 September 2001 attacks on the United States

Instead of curbing damaging emissions, new levies would only bump up fares and damage low-cost carriers in particular, say aviation groups.


"Generally speaking, if you tax the airlines in a negative way, you're removing our ability to reinvest in new technology," said IATA's Concil.


But green initiatives such as global emissions trading schemes for airlines, under review in Europe, are gaining favour.


British Airways already participates in emissions trading and budget airline EasyJet said it would support any government moves towards an aviation emissions trading scheme.