Lower oil prices usually boost airlines' earnings, but for AirAsia, the decline pushed the carrier into the red as crude's plunge took Malaysia's ringgit with it.
AirAsia swung to a net loss of 428.5 million ringgit for the fourth quarter, its first loss in two years, after its foreign-exchange losses surged to 647.6 million ringgit from 34.9 million in the year-earlier quarter.
The ringgit has plunged nearly 13 percent against the U.S. dollar since mid-2014, trading around levels last seen in 2009, during the Global Financial Crisis. Despite recovering somewhat this month, Brent crude prices have nearly halved since the middle of last year. Petroleum products and liquefied natural gas account for 14 percent of Malaysia's exports.
The blow to the ringgit pushed up the cost of AirAsia's foreign-currency debt and operating costs.
"The loss is only a paper loss from foreign currencies," AirAsia's CEO Tony Fernandes told CNBC Friday, noting balance sheet items need to be revalued and included in earnings.
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That masked a "huge profit," he said, noting revenue rose 16 percent.
AirAsia's fuel cost is effectively around $80 a barrel, compared with $120 in the previous quarter, he said.
But the carrier may not have felt much of a fuel impact in the fourth quarter.