On April 5, China Eastern Airlines (CEA) announced that pilots involved in "turning flights back midway" would be penalized if they were found to have acted on grievances rather than "poor weather."

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

Media reports have 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.

The Civil Aviation Administration of China (CAAC) has sent a team to investigate on April 5. A CAAC spokesman said the administration was concerned about the incident on March 31 and required the CAAC southwest bureau to deal with it to ensure airlines operation. On April 1, the airport resumed operation without stranded passengers by the afternoon.

The spokesman said the agency would ask the proper authorities to impose severe penalties on the pilots if they disrupted flights on purpose, which is against professional ethics.

He added the the agency would make efforts to protect consumers' rights, ensure flight safety and promote sound development of aviation industry.

The Yunnan branch of CEA promised compensation to affected passengers that would reflect the fares paid.

A source from CEA said that the carrier had faced complaints from passengers, some of whom had got 400 yuan (US$57) to 500 yuan in compensation.

Some passengers speculated that weather wasn't the real problem. This past week, there have been reports in the Chinese media that pilots were engaging in industrial action.

A passenger surnamed Wang, headed for Beijing, said that he planned to leave Xishuangbanna at 7:40 p.m. on March 31 on flight MU5715 but the plane did not arrive in Xishuangbanna until midnight. "I will not get back to work on time." said Wang. He said that he had already faxed CEA, which had promised to resolve the problem within three working days.

When asked about this, CEA's customer service department cited severe weather. But some passengers weren't satisfied with this explanation and plan to seek compensation.

Yuan Yiting and Li Qin, from Hangzhou, Zhejiang Province, came to the customer service counter at Kunming airport on April 4, demanding that CEA compensate them for losses.

They said they were among 10 passengers who came to Kunming airport on March 31 to board flight MU5760 to Lijiang, but the plane did not arrive until 8 a.m. the next morning.

When they finally took off, the plane turned around in mid-flight and flew back to Kunming. "I could even see the aircraft runway in Lijiang airport and it was really sunny that day," said Yuan. "I insist on being compensated."

This week, media reports said a pilot strike loomed large in China as 40 Shanghai Airlines' pilots had called in sick on March 14. At the new Wuhan-based East Star Airline, 11 pilots asked for sick leave on March 28.

The reports said that pilots were angered by being required to sign 99-year (lifetime) contracts with state-owned airlines that call for them to pay their employers up to 2.1 million yuan in compensation if they quit. Airlines in China, which are mostly state-owned, directly pay the high costs of pilot training.

China has 12,000 civilian pilots. But official figures predict that the total number of flights would increase 80 percent by 2010 and 6,500 more pilots would be required.

It generally costs a Chinese airline about 700,000 yuan (about US$100,000) to 1.8 million yuan to train a pilot.