HONG KONG (AFP) - Hong Kong's Cathay Pacific Airways swung to a first-half net profit of HK$24 million (S$3.9 million) on Wednesday, but warned of continued high fuel prices and a challenging business environment.

The profit for the six months ending June 30 comes after the blue-chip Asian airline suffered a first-half net loss of HK$935 million a year earlier, representing a 103 per cent upswing.

Revenue fell 0.6 per cent to HK$48.58 billion.

Company chairman Christopher Pratt said fuel costs decreased 8.5 per cent compared to the same period last year but remained expensive, accounting for 39 per cent of total operating costs.

"We continued to operate in a challenging business environment in the first half of 2013, though there was improvement in our passenger business," he said in a statement.

Passenger numbers increased 1.3 per cent to 14.50 million.

"The persistently high price of jet fuel continued to affect our business adversely," he added.

Cathay said it had helped combat high fuel prices by withdrawing older planes and operating more long-haul services using fuel-efficient Boeing 777-300ER aircraft.

The profits fell short of analysts expectations of HK$721 million according to Dow Jones Newswires.

"While we continued to operate in a difficult environment in the first six months of 2013, it was pleasing to see some improvement in our business," said Mr Pratt, describing the business outlook for the rest of the year as "unclear".