Hong Kong "will start suffering" because of a lack of airport capacity - as does London - if a third runway is not built, an international airport group has said.
Dr Rafael Echevarne, economics director of Airports Council International, said a new runway was essential for the city to maintain its leading role in aviation in the region. It would also benefit the Pearl River Delta region, he said.
The Airport Authority and the government have proposed building a third runway as the airport will reach its capacity limit by 2018. The HK$130 billion project will require the reclamation of 650 hectares of land, and concerns have been raised about potential noise and air pollution.
Echevarne said a new runway in Hong Kong would bring more benefits to the region than having it in other cities like Shenzhen or Guangzhou because of the Hong Kong airport's greater international connections. But if it was not built, there would be a "huge economic impact" on Hong Kong, he said.
"The new runway has to be where the men already are," he said. "It's like a snowball effect. When there are lots of connections, many more airlines will want to use the airport."
Echevarne said the city could focus on increasing its freight capacity and further develop the airport's connectivity if it was worried about its capacity to handle tourists. The airport handled over 4.12 million tonnes of cargo last year, the most in the world.
Hong Kong could end up in the same situation as London if nothing was done, he said. London's biggest airport, Heathrow, has not had a new runway for 60 years. It is estimated that Britain loses £1.1 billion (HK$14.3 billion) each year because of Heathrow's limited capacity and need for a new runway.
One reason Heathrow shelved a project for a third runway in 2010 was because the social costs of building the runway were found to be as high as its estimated economic benefits.
A study recently found that land reclamation for the proposed third runway in Hong Kong could cause the loss of the pink dolphin habitat off Lantau, and that would cost the city HK$36.1 billion over 10 years.