China’s two major airlines posted shrinking profits in the third quarter due to lackluster demand and foreign exchange losses.

Air China Ltd said late Tuesday that its third-quarter net profit dropped 16.46 percent to 3.2 billion yuan ($508 million) from the same period last year. The Beijing-based carrier had a net profit of 4.2 billion yuan in the first nine months, down 46.1 percent.

Air China said that rising financing costs and the yuan depreciation against the US dollar are the major causes behind the decline in profits.

The weakening yuan brought about 3.47 billion yuan in additional financing costs for the carrier in the January-September period year-on-year.

China Eastern Airlines Co Ltd, one of the nation’s major three airlines, said late Tuesday that its third-quarter net profit was 2.6 billion yuan, down 20.36 percent year-on-year.

Due to the depreciation of the yuan against the US dollar, China Eastern saw its financial expenses surge to 586 million yuan from a negative 309.6 million yuan a year ago.

On Monday, China Southern Airlines Co Ltd — the nation’s largest carrier by fleet size — said its net profit in the third quarter was 2.2 billion yuan, a drop of 29.25 percent year-on-year, but a sharp rise of 1,604.6 percent quarter-on-quarter.

The peak season, including the summer holidays and the National Day holidays, meant more income for the Guangzhou-based carrier, while increasing investment income also helped to boost its earnings. However, a rapid rise in jet fuel prices and the weakening yuan have partly offset the positive impact.