Following the anti-Beijing protests by some of Cathay Pacific Airways Ltd.’s employees, China has issued a stern warning to the Hong Kong-based airline. Hong Kong has been swathed with Beijing demonstrations over the last few months, including a three-day sit-in at the city’s airport.

The Civil Aviation Administration of China has issued a warning to Cathay, ordering the airline carrier to ban all employees that are a part of or support the Beijing protests from flying to the mainland starting on Saturday, Bloomberg reported.

In its warning to the airline, the Civil Aviation Administration of China said, Cathay’s actions “have led to a severe threat to aviation safety, created negative social impact and increased the risk of flying from Hong Kong to the mainland.”

The administration has also ordered Cathay to provide information on all crew members that fly to the mainland for verification and authorization starting on Sunday. This is in addition to submitting a plan to enhance internal controls, flight safety, and security by Thursday, according to the Civil Aviation Administration of China.

A spokesperson for Cathay told Bloomberg, the airline is treating the Chinese administration’s directives very seriously and will not tolerate behavior that could affect aviation safety.

China is seen as Cathay’s most important market with about half of the company’s revenue coming from flights between the country and Hong Kong, according to the news outlet. The company has reportedly said that its ticket sales were affected in July by the protests and it is continuing to hurt future bookings with the airline.