China Southern Airlines said on Tuesday that it has signed a deal with Boeing to buy 55 Boeing 737s to meet rising market demand and renew its fleet.

The aircraft, including the 737-700 and 737-800 models, would be delivered between May 2011 and October 2013, said a statement from China Southern, the country's largest carrier in terms of fleet size.

China Southern would pay for the aircraft at a discount with its own funds and loans from commercial banks, said the statement.

But the company did not disclose the value of the deal or the number of each model.

At catalog prices, a 737-700 costs US$57 million to US$67.5 million, while a 737-800 costs US$70.5 million to US$79 million.

In the past year, China Southern has bought 92 Boeing 737s, six Boeing 777 freighters and 20 Airbus 320s, which would raise its transport capacity by 32.8 percent, reported Tuesday's China Securities Journal.

The company, based in the southern city of Guangzhou, carried 49.21 million passengers last year, making it the only carrier on the Chinese mainland among the world's top 10 passenger transport airlines.

The company also said on Tuesday its net profits in the first half of the year rose 136.07 percent to 308 million yuan (US$40.5 million).

Earnings per share were 0.07 yuan in the first half.