Hong Kong Airline Carrier Cathay Pacific seen in Hong Kong International Airport. Artur Widak | NurPhoto | Getty Images

Cathay Pacific shares fell more than 4% on Monday after the carrier announced it had suspended a pilot for his involvement in Hong Kong's anti-government protests. The airline said Saturday that employees who "support or take part in illegal protests, violent actions, or overly radical behaviour" would be barred from crewing flights to mainland China. It also confirmed that one of its pilots was removed from his duties since July 30. The pilot was reportedly among over 40 people charged with rioting, during clashes with police near Beijing's main representative office in the city. Hong Kong — a former British colony that was returned to Chinese rule in 1997 — has been struggling to end weeks of protests that have in recent weeks turned increasingly violent and disruptive. The rallies, which were started to protest a bill that would have allowed people to be extradited to mainland China, have snowballed into a democracy movement, with some even demanding full autonomy from Beijing. The unrest has frequently crippled the Asian financial hub's transportation system and last Monday, Cathay cancelled hundreds of flights during a general strike.

China cites aviation 'threat'

Cathay's decision came a day after China's aviation authority issued a "major aviation safety risk warning" to the airline. The Civil Aviation Authority said that "on multiple occasions," Cathay's flight personnel have participated in "violent assault," according to CNBC's translation. "The incidents pose a serious threat to aviation safety, causing adverse social impact and as a result is increasing inbound aviation safety threats from Hong Kong to the mainland," it said. It also ordered the carrier to provide identification information for its crew on mainland-bound flights, and said that crew members that do not receive the authority's approval will not be allowed into its airspace, including on flights bound for other destinations. As the protests continue, many businesses have voiced their concerns about losing access to the world's second largest economy. Involvement by the aviation authority in China could raise more questions about whether businesses will have to take sides.