The Civil Aviation Administration of China has vowed to take tougher measures to improve punctuality.

Airlines with a less than 50 percent on-time departure rate and which rank among the last 20 percent on punctuality will be issued a warning and asked to take remedial measures.

If a route is given two warnings in a month, the authority will revoke the airline's license for that route.

If a flight is delayed for more than four hours, resulting in huge protests due to bad arrangements, the airline will be stopped from operating the route.

Zhang Wuan, spokesman for Shanghai budget carrier Spring Airlines, said the company's punctuality level has remained at about 80 percent over the years.

"Usually, we reserve a certain number of aircraft and crew in case of any emergency," he said. "In addition, we cut down flying hours for our crews during the summer to ensure they won't work overtime."

Flight schedules are arranged several months in advance, he added, and in most cases delays are not caused by airlines.

"Many passengers may have had to wait on board for hours before takeoff and this is usually caused by air traffic control," Zhang said.

China's eight busiest airports, including Beijing, Shanghai, Guangzhou and Shenzhen, have been prohibited from using air traffic control as an excuse for delaying flights, according to sources.

One unidentified source with the air traffic management bureau under the Civil Aviation Administration of China was quoted by the Oriental Morning Post as saying the bureau is looking at the consequences of the new measures.

According to insiders, air traffic control is often used as a convenient, catch-all excuse, and can refer to extreme weather, military use of airspace, equipment failure, or an ill-arranged schedule.