SHANGHAI (AFP) - Chinese budget carrier Spring Airlines said it plans to buy 21 Airbus A320 planes for 12.45 billion yuan (S$2.75 billion), citing growth in both international and domestic air travel.

The Shanghai-listed company plans to fund the purchase in part through a private placement of shares to raise 4.5 billion yuan, according to a statement to the exchange late Monday.

The single-aisle A320 has a list price of US$97 million, according to Airbus.

"Demand in China's domestic and international aviation market is steadily increasing," Spring said in the statement. "The company intends to reasonably expand the scale of its fleet to increase its air transport capacity."

Spring Airlines, headquartered in the Chinese commercial hub of Shanghai, was founded in 2005 and now flies more than 90 domestic and international routes, according to its website.

China, the world's second-largest economy, is already Asia's biggest aircraft buyer as a growing middle class takes to the skies in ever-increasing numbers.

Last year, US aircraft giant Boeing forecast Chinese carriers will need nearly 6,000 new planes valued at US$780 billion over the next 20 years, accounting for around 16 per cent of world demand and nearly half of Asia's.

But Chinese growth is slowing and expected to soften further in the coming years - a trend industry officials say could put a dent in air travel.