The European Union's parliament wants stricter aviation emission targets as part of plans to tackle climate change and cut levels of greenhouse gases.
Critics say the plan will make tickets more expensive
At present airlines are not part of a EU-wide carbon trading system that applies to other polluting industries.
Under the plans, airlines operating to or from the EU would have to join a cap-and-trade emissions system by 2011.
Critics say the tougher rules would increase ticket prices for passengers, and do little to slow global warming.
The existing cap-and-trade system already applies to other sectors - mainly heavy industry and energy firms.
Under its rules, if firms cannot meet the targets set for their industries, then they have to buy extra permits allowing them to pollute further.
Aviation is an environmental battleground as critics of the industry fight to impose stricter rules and make it more responsible for the effect it has on the environment.
At the same time, airlines complain that they are being unfairly targeted, arguing that planes are becoming more efficient, quieter and less polluting and still only account for a fraction of the world's total emissions.
The latest draft of the plans to limit aviation emissions would apply stricter rules than those originally proposed in December by the European Commission.
Under the revised terms, each carrier would be allowed to emit 90% of its average emissions between 2004-2006 without charge.
However, if it exceeded that level, then it would incur extra costs.
In the previous version of the rules, which were proposed by the European Commission, non-EU carriers would have had an extra year to join the scheme and been allowed to cap emissions at 100% of 2004-2006 levels.
While the aviation industry has said that EU's plans could damage its business, some opponents have claimed that localised attempts to tackle global warming are not sufficient and do not go far enough.
"It has always been clear that the European Union Emission Trading Scheme (ETS) was only ever going to be a first step in tackling emissions from aviation," said Kirsty Clough of environmental campaign group WWF.
Ms Clough added that further measures and policies were needed.
The US has said that if the EU goes ahead with the plan then it could face a trade battle, arguing that non-EU airlines come under the authority of the International Civil Aviation Organisation, not the EU.