The Pearl River Delta is one of the most infamously congested parts of China’s airspace and now work is underway on another runway there, with yet one more likely to follow soon—and then a sixth airport.

None of the five airports in the Pearl River Delta is more than 154 km (95 mi.) from another; most of the distances are much shorter. There are eight runways, some aligned north-south and some east-west. To make matters worse, the Chinese air force allows little space for civil use and peculiar regulations for the border with Hong Kong force aircraft onto circuitous routes.

Guangzhou Baiyun International Airport, mainland China’s second-busiest, has begun work on an expansion program that will more than double its capacity. Commencement of the work follows confirmation by the national government last month that Guangzhou will serve as one of the country’s three main international aviation gateways—even though the great majority of southern China’s intercontinental connections are at Hong Kong.

Guangzhou’s Communist Party committee is also pressing ahead with studies on a second airport for the city, although it provides no details except that the airport will be in the southern districts. Baiyun, home of China Southern Airlines, is in the north.

Competition among airports in the well-developed Pearl River Delta is already strong. Apart from Baiyun and Hong Kong International Airport, the region has Shenzhen Baoan Airport, Macau International Airport and, the weakest of the five, Zhuhai Sanzao Airport. Hong Kong is 135 km from Guangzhou and less than 60 km from the other three.

The busiest airport in the region is now Hong Kong, with 54 million passengers last year, but expansion at Baiyun is intended to prepare that facility to handle 80 million passengers in 2020. It handled 45 million last year; more than 50 million are expected this year. The current runways and terminal were designed for 25 million travelers but can cope with 35 million, say local media, so the facility is already grossly overloaded.

The main features of Baiyun’s upgrade are a 3,800 X 60-meter (12,500 X 200-ft.) runway able to accommodate any class of commercial aircraft and a 595,000-sq.-meter Terminal 2, says the National Development and Reform Commission, which authorized the work. The runway is due to be completed in 2014 and the terminal in 2016. The two runways are nearing their capacity of 1,000 movements a day, a ceiling set presumably by conservative Chinese air traffic rules.

The third runway will be only 400 meters east of the current eastern runway, according to local media reports. That should limit its contribution to movement capacity—and to the congestion. Baiyun’s landing guidance system will be upgraded to Category 2, and the airport will have an apron that can serve 100 aircraft, a new air traffic control operations building, new radars, more car parks, a metro station and four 10,000-cu.-meter fuel tanks that will be supplied from outside the facility by a 100-km pipeline. The budget is 18.9 billion yuan (US$3 billion), of which 800 million yuan will come from the aviation development fund.

Despite the air traffic congestion, demand is driving other airports in the region to add runways. Shenzhen completed its second last year and Hong Kong’s government has given in-principle approval for a third. “More runways do not necessarily provide more capacity if the airspace congestion issue cannot be resolved,” write researchers of the Aviation Policy and Research Center of the Chinese University of Hong Kong, calling for reforms. They estimate that congestion costs more than HK$1 billion (US$130 million) a year in fuel alone.

Jiang Huaiyu, director of the central and southern region of the Civil Aviation Administration of China (CAAC), told a conference of the region’s airports last year that Shenzhen’s second runway could support no major traffic growth because of congestion.

More optimistically, Law Cheung-Kwok, associate director of the aviation center at the Chinese University of Hong Kong, reckons that while the expansion of Guangzhou will surely demand further liberalization of the airspace, recent experience suggests that the air force will cooperate with the CAAC in opening up more access.

Further challenges loom, however. As authorities steadily remove restrictions, they must look toward a sixth airport in the region since the expansion at Baiyun could well be the last major upgrade for that facility.

Zhang Kejian, chairman of the facility’s listed operating company, last year said international experience suggests airports tend to become more efficient as they grow, but not past a capacity of 80 million passengers a year, or at most 100 million. Beyond that, it is better to build another airport, he says. That explains Guangzhou’s studies for another facility and Beijing’s decision to build another airport rather than further expand Capital Airport, China’s busiest.