Cathay Pacific staff reportedly claim they fear losing their jobs if they voice support for pro-democracy protesters in Hong Kong.
Employees of the airline told the BBC that staff feared working routes to mainland China.
Some are considering bringing decoy mobiles with them in case their phones are checked on arrival in the mainland.
The concerns emerged weeks after China demanded the airline suspend staff involved in the protest movement.
Protesters have been taking to the streets of Hong Kong for the past 11 weeks. The demonstrations were originally against an extradition bill but have now evolved into a wider pro-democracy movement.
The Hong Kong-based carrier reportedly fired two pilots over protest-related incidents earlier this month.
One cabin crew member who wished to remain anonymous told BBC Newsnight: “We try not to talk about politics during a flight because you don’t know which colleagues are at your side. The company says that we should not support the ‘illegal’ protests.
“So if somebody who is pro-China finds out you went to the protest, they find some way to report you to the company. Maybe not for a political issue but for some safety issue that might mean you lose your job. So we are not able to talk in the flights.”
Some fear being detained while working routes to mainland China.
The airline’s new CEO Augustus Tang told staff on Monday that there was “zero tolerance for illegal activities” or policy breaches.
He said in a memo to staff: “The way every single one of us acts, not only at work serving our customers but also outside work – on social media and in everyday life – impacts how we are perceived as a company.”
Tam said: “How can you control people who are doing this in their own time? This is not Hong Kong at all. We have freedom of speech here. We have our own jurisdictions and our own common law.
“We stand together through the good times and bad times. During the Second World War and Japanese occupation and during the Asian financial crisis of 1997.”
The BBC said it had contacted Cathay Pacific for comment. The airline earlier told Reuters that it would not comment on internal staff matters.