A challenging outlook for the global air freight industry has prompted Changi Airport Group to offer about $14 million in rebates for firms in the industry.

A one-time rebate for cargo carriers and firms helping companies organise transport of goods by air was unveiled by the group.

The group also extended an incentive scheme providing firms rental rebates based on the volume of cargo handled, on cargo facilities they are leasing from it.

With these measures, carriers and firms can potentially enjoy a rebate of up to 45 per cent of annual rental, Changi Airport Group said.

Also, it extended the 30 per cent landing fee rebate for regularly scheduled cargo flights to March 31 next year.

The initiatives are to provide more cost support to these firms.

Air cargo demand has been subdued by a tough global economic environment, feeble world trade and a slowdown in China's economy, the group said in a statement.

Global air freight volumes experienced modest growth of 2.2 per cent last year, which was slower than 2014, it noted.

Mr Lim Ching Kiat, senior vice- president for market development at Changi Airport Group, said: "The soft industry outlook is likely to continue in 2016, due to continued headwinds brought about by weaker economic conditions and slowing global trade.

"In the light of the trying business conditions, we are committed to support our cargo partners through these difficult times."

Last year, the amount of cargo handled by Changi Airport grew 0.5 per cent over the year before to 1.85 million tonnes. Transshipment volumes grew but import and export volumes fell. Pharmaceuticals was one of the best performing cargo segments at Changi Airport last year, growing 45 per cent from 2014, albeit from a small base. Also, three airlines started delivering cargo to Singapore last year.

The manufacturing slowdown has caused firms to import and export fewer goods by air, Mr Steven Lee, chairman of the Singapore Aircargo Agents Association, said.

Revenue to cargo airlines and companies which coordinate air transport of goods had fallen on a broad level by about 15 per cent compared with 2014, he said, adding that the initiatives were "a very positive move".

Mr Freddy Chong, business development manager for 3R Logistics, said that firms were using cheaper means to transport their goods such as by sea, owing to the economic slowdown.

Revenues from air freight logistics services had fallen about 10 per cent in the past year compared with 2014 at his firm.