BEIJING - China is cracking down on airline passengers who change seats, smoke and wander the cabin at inappropriate times, threatening them with fines of up to 10,000 yuan (US$1,300), local media reported on Friday.

Airlines in China have previously taken a relaxed attitude to the flouting of in-flight rules, with cabin staff invariably ignoring the stowing of oversized luggage and allowing fliers to swap seats at will.

But in a sign of changing times, 18 Chinese air marshals last month completed two weeks of training in the United States on how to be armed undercover officers aboard passenger jets.

Under new regulations, passengers who changed seats without cabin staff permission would face "fines from 500 to 10,000 yuan", the Beijing News said.

"At the same time, passengers who leave their seats or open luggage compartments during take-off, landing or turbulence would also be fined," the paper said.

The rules also allowed fines for ignoring cabin staff orders, smoking, stowing oversized and overweight hand luggage, "creating disturbances" and 13 other sort of behaviour, the paper said.

Separately, China's aviation authority is under fire after a computer failure caused a series of check-in service breakdowns in major airports this week, Xinhua news agency reported.

The failure on Tuesday afternoon delayed check-in services and postponed 33 flights in Beijing, and others in Shanghai and Guangzhou, the report said.

A similar failure had resulted in the breakdown of the departure control system in January, affecting airports in Beijing, Shanghai, Chengdu and other cities, Xinhua said.

China's commercial aviation industry is expanding faster than the country can build infrastructure and train pilots.

Strained airports and cramped flight space have caused increasing flight delays and cancellations and regular reports of furious passengers staging sit-in protests on planes and demanding compensation.