The body grouping the world's airlines warned Tuesday that hitting a target of five percent sustainable fuel by 2030 is "extremely ambitious" if not impossible.

Producing enough sustainable aviation fuel (SAF) would require investment in locations across the world, the head of the International Air Transport Association said.

"We're not going to promise to achieve something that we don't believe is possible," director general Willie Walsh said during annual talks in Dubai.

"I believe that five percent SAF in 2030 is extremely ambitious. I think it will be achieved and maybe even exceeded in certain parts of the world.

"But when we look at where SAF is being produced and where investments are being made, it's very clear to us it won't be achieved in every part of the world."

However, Walsh said IATA's goal of net zero carbon emissions by 2050 remained on track.

The five percent SAF target was set by a United Nations agency, the International Civil Aviation Organization, at the end of last year.

"It wasn't that IATA pushed for a five percent target in 2030," Walsh said, adding: "Obviously, we'll do everything we can to deliver as much as possible."

On Sunday, IATA said SAF production would triple this year to 1.9 billion litres (1.5 million tonnes), representing 0.53 percent of airlines' total fuel needs.

About three percent of global CO2 is produced by the air industry, which is mainly looking to SAF to reach its goal of net zero emissions by mid-century.