China Southern Airlines, the country's largest airline by fleet size, said Sunday its third quarter net profit fell 29 percent compared to a year earlier due to foreign exchange losses.

The airline reported that net profit fell to 2.22 billion yuan ($355 million) in the three months ended September 30, from 3.13 billion yuan in the same period a year earlier, the company said.

The Guangzhou-based airline reported 518 million yuan net finance expenses for the third quarter and attributed it to the "depreciation of RMB against the USD", it said in a filing to the Hong Kong stock exchange.

The fluctuation between the Chinese yuan and the US dollar is a major factor in the airline's profitability because much of its aircraft purchasing costs are in US dollars, Dow Jones Newswire reported.

The airline in February ordered 10 extended-range versions of the twin-engine Boeing 777 in a deal valued at nearly $3 billion.