Beijing Capital International Airport welcomed its 80 millionth passenger this year on Wednesday, reaching its designed capacity five years ahead of schedule.

It remains the world's second-largest airport in terms of passenger traffic, trailing only Hartsfield-Jackson Atlanta International Airport in the United States, which handles nearly 90 million passengers a year.

Passengers wait in lines to check in at Terminal 3 at Beijing Capital International Airport earlier this year. Zhuo Ensen / for China Daily

Wang Yi, the 80 millionth passenger at the capital airport this year, arrived on a China Southern Airlines flight from Guangzhou at noon. When asked how he felt about the airport, he said it is "a little bit crowded".

Industry insiders said "crowded" will be the word that passengers think of when they walk into the capital airport, before the second capital airport of Beijing opens around 2018.

The airport estimated it will handle 81.6 million passengers this year.

It took just two years for the number of passengers to increase from 70 million a year in 2010 to 80 million this year, and the airport estimates that the yearly total will exceed 90 million by 2015.

The second capital airport, which is expected to divert much of the growing traffic, will not open for another five or six years, according to Li Jiaxiang, head of the Civil Aviation Administration of China.

"We have to come to a point that, whether willingly or not, we must come up with new plans to solve the problem along with the rapid growth of air traffic," Zhang Guanghui, general manager of the capital airport, said on Wednesday.

He said the airport is currently "researching what resources, both in the air and on the ground, can be used".

He said the capital airport was designed with a fourth runway, which can increase passenger capacity by at least 10 to 15 percent. But due to the limited airspace available to civil aviation, building the fourth runway has not been on the airport's agenda.

Ouyang Jie, a professor at the Civil Aviation University of China who specializes in airport studies, said the three runways at the capital airport have almost reached their maximum capacity due to the limited airspace.

"Adding a fourth won't help with the traffic pressure, because without enough airspace, planes won't be able to take off or land on the additional runway," he said.

"The airport's infrastructure will have no problem handling 90 million or more passengers a year in the coming years, but the airport will have to sacrifice its service quality," he said.

He suggested the capital airport divert some of its domestic passenger traffic to neighboring airports, such as Tianjin or Shijiazhuang.

It's a feasible option because the airports in the two cities are connected to Beijing by high-speed trains with only an hour's travel time, he said.

But industry insiders said the market may not accept the arrangement, and most passengers may not opt for flights to Tianjin or Shijiazhuang instead of Beijing.

Zhang, the airport's general manager, said the airport is planning to use an idle section in the third terminal building that was originally reserved for handling international travelers.

The section will be used next year to handle the overflow in domestic air traffic.

Contact the writer at xindingding@chinadaily.com.cn