Eight major mainland airports are trying to reduce flight delays by ordering commercial planes to take off on time - even if they have no landing slot at their destination. The drastic move, ordered by aviation authorities, could lead to planes having to circle airports for hours waiting for clearance to land and has been slammed as unsafe and impractical. Waiting on the ground is always safer than waiting in the air Yang Xinsheng, dean of the College of Air Traffic Management at the Civil Aviation University of China, said it was "ridiculous" and added: "Waiting on the ground is always safer than waiting in the air." The measure was implemented last week after mainland airports were found to be among the worst in the world for delayed departures and arrivals. The measure - termed "unrestricted take-off" - took effect at Beijing Capital, Shanghai Hongqiao, Shanghai Pudong, Guangzhou Baiyun, Shenzhen Baoan, Chengdu Shuangliu, Xian Xianyang and Kunming Changshui airports. Together they account for half the mainland's air traffic. The Beijing News said the measure had "effectively improved" performance. It said Beijing Capital International Airport increased its rate of on-time departures by 15 to 20 per cent. But experts and members of the public remained sceptical. Yang said that if planes were allowed to take off without securing a landing slot at the destination first, they could end up circling in the air for hours. Caught on camera: Air rage incidents from around China Airlines will also have to pay much more for fuel. The extra flying hours could also add to the stress and pressure on air crews. "I don't think passengers would want this either. Taking off on time may reduce anger, but circling around the airport could induce panic," he said. An aviation expert based in Hong Kong, who asked not to be named, said it was a common practice at many big international airports to ask planes to circle before getting landing clearance. But he said: "This puts great pressure on air traffic control - and the mainland's [civilian] air traffic control is not among the best. "They also have to deal with heavy interference from the military, so there could be safety concerns. This could well be an experiment by the government to squeeze efficiency. "They may want to push the limits to test what traffic controls are necessary and what could be relaxed to reduce delays," he said. Previously, the central government told China News Services that 42.3 per cent of flight delays were caused by airline management problems. Another 26.1 per cent were caused by air traffic control, 20.9 per cent by the weather and 7 per cent by military exercises.