Airlines across the world are looking to clean up their act, and SIngapore has agreed to be part of the global effort.

It says it intends to join a voluntary scheme being proposed by the United Nations to cap the aviation industry's carbon footprint.

If things go as planned, from 2021, all Singapore carriers, including Singapore Airlines (SIA), Scoot-Tigerair and Jetstar Asia, will have to offset or neutralise carbon dioxide emissions. They will likely do this by investing in projects to reduce carbon emissions - such as wind farms.

The International Civil Aviation Organisation (ICAO) - the UN's civil aviation arm - wants the scheme to start on a voluntary pilot basis in 2021, and make it compulsory from 2027 for most countries.

ICAO's proposal will be up for discussion and endorsement by its 191 member states at the organisation's upcoming assembly from Sep. 27 to Oct. 7 in Montreal, Canada.

The extra cost of the scheme, to be borne by airlines, could end up being passed on to travellers, industry analysts said. But they noted that given the intense competition, airlines would be careful about doing so.

Ultimately, fares are a function of supply and demand, said SIA spokesman Nicholas Ionides.

Civil Aviation Authority of Singapore director-general Kevin Shumsaid Singapore supports ICAO's plan, which "avoids a patchwork of national and regional" schemes.

Singapore intends to participate in the pilot phase of the scheme, on the understanding that enough members also take part.

"This is to ensure that the scheme is able to function effectively, and provides for a level playing field that minimises market distortion," Mr Shum said.

Apart from Singapore, the United States, China, Canada, Indonesia, Mexico and 44 European countries have all said they would participate in the scheme, said Mr Alexandre de Juniac, director-general and chief executive of the International Air Transport Association (IATA).

Together, carriers from these countries account for about 70 per cent of global air traffic, he said.

While IATA was previously working towards an industry-wide implementation of a carbon offset scheme by 2020, it fully supports ICAO's plans, including the six-year pilot phase.

Mr de Juniac, who recently took over as IATA chief, said: "The key priority is to have the decision made and the system adopted by states. If it then takes longer to implement it effectively, it is frankly a secondary issue."

Airlines account for about 2 per cent of man-made global carbon emissions, but there are fears this could triple by 2050, given the growth of air travel.

Even as Mr de Juniac expects "a few weeks of difficult negotiations", IATA is optimistic that there will be global consensus, he told reporters in Singapore yesterday.

With its resources and know- how, IATA is happy to help run the programme on behalf of ICAO and states, he said.