China Eastern Airlines, the country's second-largest carrier by passenger numbers, forecast that its full-year profit will dive 53 percent-59 percent to between 2.6 billion yuan and 3 billion yuan. The company is expected to post its earnings in March.

"The company's annual fuel cost increased significantly in 2018 as the average fuel price rose. The weakening of the yuan exchange rate during the reporting period caused the company to suffer exchange losses in 2018," it said.

In 2017, the airline posted a 40.9 percent jump in profit year-on-year to 6.35 billion yuan ($1 billion), the highest since at least 1996, Thomson Reuters data showed.

The company's full-year profit was supported by a one-off sale of its cargo shareholding.

Meanwhile, China Southern Airlines, the country's largest carrier by passenger numbers, said in a separate statement that it expects its full-year profit to dive between 47 percent and 56 percent as costs surged. The carrier's net profit came in at 5.91 billion yuan in 2017.

While Chinese airlines have witnessed a revenue surge in tandem with growing demand for travel, their costs have increased due to a volatile currency and rebounding oil prices.

The yuan lost about 5.3 percent of its value against the U.S. dollar in 2018, pushing up financing costs at airlines, which have bought planes with mainly U.S. dollar-denominated loans.

Shares in China Eastern closed 0.4 percent higher on Wednesday, before the full-year outlook was announced. In October, the carrier had posted a 38 percent drop in third-quarter net profit.

(Reporting by Brenda Goh, Editing by Sherry Jacob-Phillips)

By Brenda Goh