Rebecca Sy was wheeling her carry-on luggage through Hong Kong International Airport ready to board a flight to China when she received the message that changed her life.

Key points: Hong Kong has been gripped by pro-democracy protests since June

Hong Kong has been gripped by pro-democracy protests since June Some Cathay Pacific staff say they have been sacked unfairly due to Chinese pressure

Some Cathay Pacific staff say they have been sacked unfairly due to Chinese pressure Cathay Pacific says it adheres to all aviation and employment regulations

The Cathay Pacific flight attendant with 17 years of experience had trekked through the terminal countless times before, across its hundreds of metres of tiles and travelators.

But this walk to the gates was cut short.

"I received a message that I needed to return home and wait for someone from the company to call," Ms Sy said.

She was summoned to a meeting the following day with Cathay Pacific executives.

In the days before, China had made clear it had zero tolerance for staff supporting the pro-democracy protests that were shaking the airline's home city.

Rebecca Sy (right) had 17 years of experience as a flight attendant. ( Supplied: Rebecca Sy )

When she entered the conference room, she saw printed screenshots of her Facebook posts laid out on the table.

She said one showed the words 'happy birthday' she had written on sticky notes for a colleague.

Another printout was a screenshot from a Facebook Live story in which Ms Sy claims she had simply mourned the resignation of the company's chief executive.

The third, she said, informed her friends of an impending work trip to the mainland.

Her Facebook profile was private, so she reasoned that the posts must have been sent to management by her own friends.

Rebecca Sy (far left) first began working for Dragon Air, which later became Cathay Dragon, in 2002, and was fired this year. ( Supplied )

One of the managers asked Ms Sy whether the posts were hers, and she confirmed they were.

"Then the guy immediately said, 'I have to start the process … you're going to be terminated with immediate effect.'"

Her career of nearly two decades was over.

Ms Sy insists the posts were innocuous, and she believes there was one real reason for her dismissal.

Before she was sacked, Ms Sy was the chair of the union representing cabin crew at Cathay Dragon airlines, which operates most of the Cathay group's flights to mainland China.

As the protests unfolded, the union had released a statement defending Cathay staff's right to freedom of speech.

"Of course … it is the pressure from the Chinese Government," she said.

Rebecca Sy was the chairwoman of the Cathay Dragon union for cabin crew members when she was sacked. ( Supplied: Rebecca Sy )

Ms Sy said her termination hit the crew community "like a bomb".

"[My colleagues] would think even the chairperson of a union can be terminated because of her social media accounts," she said.

"That simply means everyone could be sacked as well."

Fear of China turns colleagues against each other

Major demonstrations began in Hong Kong in June over an extradition bill, but have since morphed into a broader pro-democracy, anti-China campaign.

Hong Kong's protests have at times turned violent, with police spraying tear gas at protesters at the airport in August. ( Reuters: Tyrone Siu )

Several large companies have been squeezed between Hong Kong's citizens and China's desire to quell dissent.

But Cathay Pacific is uniquely vulnerable and the highest-profile victim.

Passenger numbers in September were down by about 7 per cent on the same month in 2018, and the airline conceded demand from mainland customers had fallen particularly sharply.

Hong Kong's flagship carrier depends on China — and the one-party Communist state knows it.

The Civil Aviation Administration of China (CAAC) issued a "safety" directive banning crew who support or take part in demonstrations from landing in the mainland or using its airspace.

Cathay employee 'Jane' says pressure from China has "instilled widespread mistrust and terror" among staff. ( ABC News: Aaron Hollett )

"That changed the whole thing," said a current Cathay Pacific employee who wanted to be known only as Jane.

"It has instilled a widespread mistrust and terror among colleagues," she said.

Jane agreed to talk to the ABC only if she could conceal her face with dark glasses and a hood, and if the interview occurred in a secret location in Hong Kong.

She is one of 27,000 Cathay Pacific employees in Hong Kong and has worked for the airline for more than a decade.

Cathay Pacific warns staff against breaching its strict code of conduct, which outlaws any activity that could prevent the airline meeting "any applicable legal or regulatory requirements".

And whistleblowing policies encourage staff to confidentially report any suspected violation by another colleague.

Cathay's whistleblowing policies allow staff to confidentially report their colleagues for suspected issues. ( Reuters: Bobby Yip )

That has fuelled paranoia and turned co-workers against one another, according to Jane.

She said "people can no longer talk freely" about anything political for fear of colleagues informing on them to management.

"It's like there is a dark hole there that everybody tries to avoid," Jane said.

"I think all of us feel that Cathay is no longer the same company we have ever known."

'This company did not deserve a crew like us'

Some feel the scrutiny from mainland regulators and consumers is so intense that staff are being sacked over issues beyond their control.

A Cathay Dragon cabin crew member who wanted to be known only as Chloe said she lost her job after she discovered a leaking oxygen tank during a flight to Malaysia.

She had heard a high-pitched noise during the flight and asked a colleague to double-check the canister.

'Chloe' says she lost her job at Cathay Dragon after she discovered a leaking oxygen tank on board a flight to Malaysia. ( ABC News: Aaron Hollett )

The entire cabin crew on board the flight was suspended, and Chloe and the colleague who found the leaking tank were sacked three days later.

"I'm the one who discovered it, I checked it, and I reported it," she told managers through tears after being fired.

Chloe said Cathay Pacific was "squeezing" frontline employees who were "so scared of doing anything wrong".

"We are just a used tissue. They just throw you out," she said.

In the space of just a few months, the airline has been transformed dramatically — and maybe permanently — by political events completely out of its control.

Its workforce understands this, but many are also disappointed by the company's response.

"This company did not deserve a crew like us," said former Cathay Dragon crew member Mixe Lee. ( ABC News: Aaron Hollett )

Mixe Lee was sacked from his job as a Cathay Dragon crew member for condemning the harsh police response to protesters inside a local shopping mall on social media.

"Hong Kong is," he said, before correcting himself, "was a place with freedom of speech, so I don't think expressing my political view will affect any relationship or especially my work".

"I still think that the staff and the crews in this airline perform very well as always. But … this company did not deserve a crew like us."

Cathay defends management style in tumultuous times

Cathay Pacific declined to directly comment on any of the cases raised in this story.

In a statement, a spokesperson for Cathay Pacific said that for staffing decisions, "all relevant factors" are taken into account, "including necessary regulatory requirements as well as the employee's ability to perform their role".

"Any actions taken by the group with regards to employees is always in strict accordance with the terms of their relevant employment contracts as well as all applicable laws and regulations."

The airline said it also must adhere to all global regulations, "including those prescribed by the authorities in mainland China".

Most Cathay Pacific journeys pass through mainland Chinese-controlled airspace, including services to Europe and the United States, and the CAAC has demanded crew lists for all of these flights.

Cathay Pacific said any action taken against staff is "always in strict accordance with the terms of their relevant employment contracts". ( ABC News: Dan Conifer )

The CAAC has lifted inspections on Cathay's fleet, after officials scoured crew members' mobile phones for anti-China content.

The ABC sought interviews with Cathay Pacific's new CEO and chairman, along with the chairman of its largest shareholder, Hong Kong-based conglomerate Swire Pacific.

No-one was available.

The ABC also contacted the regulator and the Chinese embassy in Canberra, but did not receive a response before deadline.