Civil aviation uses about a fifth of available routes of the nation's total airspace, according to Shi Boli, who heads the department of Air Transportation Regulation at CAAC. The military controls about 52 per cent of airspace in the more densely populated east, according to a report by the official China News Service in June 2011. "We are working hard and the military is also trying to improve the management of airspace," Shi said. "But, it could take some time to achieve some improvement."

In the United States, military restrictions do not have much impact on civilian aviation because its airways tend to be in desert regions or over oceans, far away from the busy airport hubs in cities such as New York, said Kevin Hiatt, president of the Virginia-based Flight Safety Foundation. The military has also allowed its airspace to be used by civilian flights on occasions such as busy holiday periods, he said.

Airspace over Europe is managed as a single unit and segregated on a "dynamic basis according to the needs of users", air traffic supervisory agency Eurocontrol said. In general, areas will only be reserved for military use at certain times and at certain altitudes.

The on-time performance rate of mainland airlines was about 74.5 per cent last year, Shi said. In the US, 82 per cent of the flights arrived on time last year, the Bureau of Transportation statistics said.

"People are hoping that the country's new leadership can have a breakthrough in getting more airspace released to accommodate the rapid growth," said Kelvin Lau, a Hong Kong-based analyst at Daiwa Securities. "Otherwise, delays will persist and hurt the airlines' long-term growth prospects."

The country's air force, which has controlled the airspace since the People's Republic was established in 1949, has started gradually relaxing some of the curbs. It had begun to open low-altitude airspace and release more information about the availability of temporary routes, Xinhua reported in August last year.

Still, the pace is not quick enough to catch up with the airlines' growth as the number of annual passengers has more than doubled in the past seven years, said David Wei, an aerospace analyst with Shanghai Securities. "The military has a bigger say in China's airspace usage for historical reasons," Wei said. "It has no incentive to concede the right unless the government wants it to."

Airspace restrictions also forced airlines to fly longer distances on some routes, said Liu Jieyin, executive vice-president at Okay Airways, which operates flights between cities including Tianjin, Hangzhou and Sanya.

"This is still better than before when we had to wait on the ground for hours for the completion of military drills," Liu said. "We couldn't take proactive measures as we wouldn't know about the drills until the last minute and couldn't tell passengers the real reason either."

Air China, Asia's biggest carrier by market value, will receive 113 aircraft in the next three years, according to a company statement. China Eastern will add 93 planes in two years while China Southern will have 67 additions this year, the carriers have said.

"Tomorrow's growth will further pressure the system," said Will Horton, a Hong Kong-based analyst at CAPA Centre for Aviation, which advises airlines. "While reforms are gradually being made, the military seems impervious to the government's wish for more airspace."