Hong Kong (CNN Business) Cathay Pacific on Monday warned its staff that those who "support or participate in illegal protests" in Hong Kong could be fired.

The city's largest airline outlined its "zero tolerance" approach in a memo sent days after Chinese authorities took steps to prevent Cathay workers who participate in protests from flying to mainland China or passing through the country's airspace. Cathay said that it would comply with that rule.

"It is important to remember that actions and words of our employees made outside of working hours can have a significant effect on the company," CEO Rupert Hogg told employees. The airline shared a copy of the memo with CNN.

"We have a high profile in the community given the nature of our business and inevitably actions of our employees frequently attract attention and would be treated as that representing the company's position," Hogg added.

All flights departing Hong Kong were later canceled Monday because of massive protests at its international airport, according to a statement posted on Cathay's website. Cathay cited a directive from the Hong Kong International Airport Authority.

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