"The ultimate phase of the airport is estimated to cost another $2 billion over the $15.5 billion," Akbar al Baker, member of the steering committee for the airport's development and chief executive of Qatar Airways, told reporters at a travel fair in Dubai.

He said the original cost of the airport, which is scheduled to open in December, was $14.5 billion, which had risen to $15.5 billion to cover an increase in passenger numbers.

The tendering process is underway for the new expansion, he said. The airport is being developed in three phases to be completed by 2015.

Qatar Airways, which plans to fly to 170 destinations over the next three years, will see its fleet size exceed 120 aircraft this year, Baker said.

The airline continues to grapple with high fuel prices despite hedging as fuel accounts for some 41 percent of its costs, he said. The airline has hedged its fuel up to 2015.

He said Qatar Airways did not need acquisitions to increase its aircraft numbers or the frequency of its services as it could sustain its growth.

"We will get into acquisition of airlines if they are well run and have shortage of equity," he said, declining to comment on whether any airlines had been identified.

Qatar's government has allocated 40 percent of its budget between now and 2016 to infrastructure projects, including $5.5 billion for a deepwater seaport, $20 billion for roads and $1 billion for a transport corridor in the capital, Doha.

(Reporting By Stanley Carvalho, Editing by Sitaraman Shankar)

• A Permanent Economic Emergency