Hong Kong lawmakers on Tuesday gave approval in principle for a third airport runway, despite concerns about pollution and noise from the $11.10 billion project.

Transport Secretary Eva Cheng said the project, estimated to cost HK$86.2 billion at 2010 prices, was needed to ensure the world's biggest cargo hub remains internationally competitive.

"The Executive Council has approved, in principle, the Airport Authority's recommendation to adopt the three runway system as a future development option for its next stage of planning," she told reporters.

She said the project was "essential for Hong Kong to maintain our competitiveness" and had the overwhelming support of the southern city's seven million people, based on the results of public consultations.

Hong Kong International Airport currently operates at a runway capacity of more than one flight a minute, with daily scheduled flights of almost 1,000, according to official figures.

The Airport Authority will now begin planning the development, including an environmental impact assessment, design and financial arrangements, Cheng said.

The planning process would take about two years, with a final decision expected by 2015.

According to an initial assessment by the Airport Authority, the new runway would cost HK$136.2 billion at 2023 prices, when it is completed.

"The final construction cost will be revised subject to the outcome of the environmental impact assessment and the associated design details," Cheng said.

The authority "must carefully study the issues of concern, such as marine ecology, noise and air quality," she stressed, acknowledging concerns that the runway could destroy marine ecosystems and worsen air pollution.

"It is of vital importance that all possible measures to avoid or mitigate such impacts must be explored."

The expansion plans would provide thousands of jobs and bring an economic benefit to Hong Kong estimated at more than HK$900 billion over 50 years.

If approved, the project would involve the reclamation of 650 hectares (1,606 acres) of land from the waters around Lantau island.

Aircraft movements rose eight percent to over 337,600 and passenger traffic rose 6.1 percent to 54.5 million in the 12 months to February, the airport said Sunday.

Cargo tonnage fell 5.3 percent to 3.9 million tonnes during the same period, it added.