The profitability of China's major air carriers rebounded in the first quarter of 2015, boosted by surging flight numbers.

China Southern, the country's largest airline by fleet, earned 27.7 billion yuan ($4.5 billion) in operating revenue in the first three months, up 6.81 percent year on year, said a quarterly financial report released on Thursday.

Its balance sheet turned from red to black, with net profits rebounding from 306 million yuan of losses to 1.9 billion yuan of gains, according to the report.

Air China and China Eastern, the other two major carriers, have yet to publish financial results, but they announced last week that preliminary accounting showed their profitability improved significantly.

Air China, the country's flag carrier, expected 1.6 to 1.8 billion yuan in net profits in the first quarter, compared with 93 million yuan in the same period last year.

China Eastern forecast 1.5 to 1.6 billion yuan in net profits, rebounding from 205 million yuan of losses in the first three months of 2014.

The Civil Aviation Administration of China said 104 million trips were made by air in the first quarter, up 12.3 percent from a year earlier.Overseas trips grew sharply by 36 percent to 9.65 million due to booming tourism.

China is expected to overtake the United States to become the world's biggest aviation market in passenger turnover by 2030, said Tony Tyler, CEO of International Air Transport Association (IATA), on Wednesday.

China's aviation industry has grown in quality as well as quantity in the past 25 years, Tyler said.

"The impressive achievements China has made to date give us confidence that even more improvements are possible," he said.

By 2034, about one fifth of the world's passengers are expected to come from China, go to China or transfer via China, he said, citing improved infrastructure such as the new Beijing international airport.

The Chinese aviation industry can improve its services in areas such as reducing flight delays, streamlining new route applications and introducing more effective air controls, Tyler said.