SHANGHAI, CHINA - China Eastern Airlines has been fined 1.5 million yuan (S$290,100) after several domestic flights returned to their departure airports in what local media described as a pilots' strike.

The General Administration of Civil Aviation of China (CAAC), China's aviation regulator, said on Thursday it assessed the fine and suspended the airline's operating licences on certain routes in southern China's Yunnan province after a probe found no technical reasons to explain most of the flights' return.

CAAC will transfer the operating licences to other carriers and has demanded penalties against China Eastern officials responsible for the incident, it added.

China Eastern made national headlines earlier this month after 21 flights operated by a unit in Yunnan province returned to their departure airports soon after taking off on March 31 and April 1.

China Eastern initially said the flights were disrupted due to bad weather but later acknowledged that a "human element" was involved. Domestic media reports said the pilots had returned to their take-off points in a protest over pay and working conditions.

China Eastern on Thursday posted a public apology on its website and promised proper handling of complaints that resulted from the disrupted flights.

"The incident has revealed that we have problems in our operations. We will take this as an important lesson," it said.

Last week, it suspended two senior executives at the unit and grounded pilots involved in the incident.

Chinese airlines are increasingly embroiled in conflicts with their pilots, who are eagerly poached by private airlines such as budget carrier Spring Airlines as the industry grapples with a pilot shortage and an air travel boom.

Many big carriers demand sizeable payments from pilots who seek to break employment contracts and move to other airlines.

Shanghai Airlines has filed suit in a local court seeking a combined 35 million yuan in compensation from nine pilots who want to leave the company, the Shanghai Daily said on Monday.

A court in Shanghai's Jingan District has accepted the case, it said. -Reuters