BEIJING, April 17, 2008 (AFP) - China's civil aviation authority Thursday stripped China Eastern Airlines of some routes and imposed a hefty fine after the carrier's pilots turned back flights in suspected industrial action.

Twenty-one flights in the southwestern province of Yunnan reversed course just over two weeks ago in what has been widely reported in the state-run press as a protest by the pilots in their struggle for better work conditions.

The Civil Aviation Administration of China said in a statement that China Eastern Airlines -- the country's third biggest carrier -- would be punished for the disruption to the services.

'We have fined China Eastern Airlines 1.5 million yuan (215 million dollars), which will be turned over to the state treasury,' the agency said.

China Eastern was stripped of the right to fly an undisclosed number of routes in Yunnan, with those services to be transferred to other airlines, according to the statement.

The administration called on the airline to uphold air safety, severely punish the people responsible and to continue investigating the reasons behind the incidents.

The original reason given for the flights being turned back was bad weather.

But a preliminary investigation by the CAA that was reported earlier found the weather at all destinations in the province was suitable for landing.

The suspected industrial action came after pilots had circulated an open letter to China Eastern Airlines demanding improved work conditions, including better pay and working hours, according to news reports this month.

Strike actions are very rare in China, where union activity is strictly controlled by the ruling Communist Party.

Employees in any industry are only allowed to belong to the ruling Communist Party-controlled All China Federation of Trade Unions.

However other pilots appear to have become increasingly bold recently.

Forty pilots for Shanghai Airlines called in sick at the same time on March 14 in another suspected industrial action.

On March 28, there were long delays for passengers with East Star Air who were trying to fly out of the central city of Wuhan, with reports saying that its pilots were locked in a dispute over working conditions.