On April 6, China Eastern Airlines (CEA) sent a work team in the morning to the southwestern Yunnan Province to investigate the flight disruptions which affected more than 1,000 passengers.

The work team consisted of a deputy general manager of CEA in charge of the safety affairs, two officials from the Civil Aviation Administration of China (CAAC) and several experts, a source with the CEA said on April 6.

On April 5, CEA announced that the pilots involved in "turning flights back midway" would be penalized if they were found to have disrupted flights on purpose.

On March 31, 18 flights returned to their departure points in the southwestern Yunnan Province, affecting more than 1,000 passengers.

Media reports said that the pilots, who work for CEA's Yunnan branch (ex-Yunnan Airlines), were protesting their pay and working conditions. The company had insisted that poor weather was involved.

According to April 5's announcement, the headquarters of Shanghai-based CEA was told that the weather did not permit landings on March 31. On the basis of that information, the company told the media that weather was the cause of the disruptions.

"We are concerned about public suspicions that weather was not the real cause and an investigation is under way," the announcement said.

CAAC sent a team to investigate on April 5. A CAAC spokesman said the administration had required the CAAC southwest bureau to ensure airlines operations.

The spokesman said the agency would order severe penalties on the pilots if they were found to have disrupted flights on purpose.