China’s civil aviation authority has ordered a flight ban on staff at Hong Kong’s biggest airline who took part in the protests sweeping the former British colony.

Any employees of Cathay Pacific Airways Ltd. who supported and joined the recent protests in the city are to be suspended from duty on flights to the mainland, the Civil Aviation Administration of China said in a statement on Friday evening. The suspension takes effect on Saturday.

The move, which marks an escalation in the way China handles companies that appear to support the protests, sends Beijing’s strongest warning yet for Hong Kong businesses and their workers to stay out of politics.

The authority also requires the airline to submit information of crew members on all flights to the mainland for verification from Sunday, as well as a plan for boosting internal control and aviation by August 15. CAAC will supervise Cathay’s implementation of the new requirements.

The economic fallout from the protests has been wide, and while China has criticized other firms for showing support for the movement, the Cathay ban is the most aggressive public move by the Asian giant against a company in the showdown.

The English-language Global Times, a subsidiary of Communist Party mouthpiece People’s Daily, warned Cathay that it would “pay a painful price” for its actions, after a trade union of the company backed protests at the Hong Kong International Airport. A Cathay pilot was arrested in the protests and released on bail, according to the report.

Cathay was already one of the latest to say its business was taking a hit in the economic fallout from the protests. Ticket sales had dipped as fewer people took Cathay flights into Hong Kong in July, and the demonstrations are hurting future bookings as well, the flagship carrier of Asia’s financial hub said Wednesday.

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Cathay hasn’t taken an official stance on the protests. A Cathay Pacific spokesperson said on on Friday evening that the airline was treating the CAAC’s directive very seriously.

“The safety of our passengers is always the top priority of Cathay Pacific," the spokesperson said. There is zero tolerance to any inappropriate and unprofessional behavior that may affect aviation safety."