There is considerable duplication of air services in Hong Kong and Guangzhou. Some 68 percent of Hong Kong airport's direct routes are also served by the Guangzhou facility.

The number of Asian airlines operating from both Hong Kong and Guangzhou increased from 18 in 2006 to 34 in 2016. The number of European airlines operating from both airports rose from four to seven over the 10 years.

Law Cheung-kwok, from the Chinese University of Hong Kong, who is director of policy at the Aviation Policy and Research Center, said another challenge facing Hong Kong airport it that it has nearly reached passenger capacity.

Before the third runway is completed in 2024, the airport's Pearl River Delta passenger volume will have dropped by 20 percent. And with the operation of a series of infrastructure projects, such as the Hong Kong-Zhuhai-Macao Bridge and the high-speed rail system connecting Guangzhou and Hong Kong, this reduced passenger volume will flow to other Bay Area airports, Law said.

But he is positive about the development of Chek Lap Kok, as both it and Guangzhou Baiyun have different market orientations, and these will remain for a long time.