AOT AOT.BK, which runs the country's six main airports, aims to boost capacity at Suvarnabhumi by 15 million to serve up to 60 million passengers in 2017, Anirut Thanomkulbutra told reporters.

The $4 billion airport, which opened in September 2006 on what was once flooded marshland known as "cobra swamp", is expected to serve about 51 million passengers in AOT's fiscal year ending in September 2012, up from 48 million a year earlier and above annual capacity put at 45 million now, Anirut said.

Construction is due to begin in 2015. Some 80 percent of the budget will come from AOT's cash and the remaining 20 percent from a domestic loan, he said, adding it had hired ECM Consortium to manage the expansion.

Bangkok's old Don Muang airport, which these days is used by private planes, budget airlines and freight carriers, will take some of the strain from July 2012 when some scheduled commercial operations will move back there, Anirut said.

"Don Muang will be opened in July and serve both domestic and international airlines and we aim to have about 8 million passengers a year," he said.

The airport operator made a net profit of 2.99 billion baht in the second quarter ending March 31, up more than two-thirds from a year earlier, thanks to the growing number of developing-world travellers and growth in low-cost air travel.

Passenger numbers to Thailand through its six airports are expected to reach 70 million this fiscal year, up from 66 million last year, Anirut said.

At the midsession break, AOT shares were up 0.9 percent at 57.50 baht, outperforming a 0.57 percent drop in the main index .SETI.

(Reporting by Manunphattr Dhanananphorn; Writing by Khettiya Jittapong; Editing by Alan Raybould)

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