A last-ditch appeal from Cathay Pacific boss Augustus Tang Kin-wing for flight attendants at the carrier’s sister airline not to take “disruptive” action was dismissed by union chiefs as only encouraging a potential strike.

FAA chairwoman Rebecca Sy On-na, who was dismissed as a flight attendant by the company in a previous incident during the city's anti-government protests last year, said: “Although we passed the motion, we won’t strike immediately because we don’t want the company to be prepared for the strike.”

She added: “We don’t want to set a timeframe [for strike] to make it more effective.”

Sy said her members would mull the options on Sunday at the rally. “We have to see how angry [our members] are ... they will decide what to do,” she added.

In a memo to all staff on Friday night, Tang said there was no legitimate basis for a strike, as the airline had taken every precaution to limit the risks involved with flying to mainland China.

With virus fears in Hong Kong growing daily, the threat of a mass strike and flight disruption is high, despite threats from the company it will discipline and even fire anyone who refuses to show up for work.

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On Thursday, Cathay Dragon CEO Algernon Yau Wing-wah was blunt about the consequences for the approximate 2,000 flight attendants, though not all are unionised.

“If you fail to report for duty in accordance with your roster, this will be treated as missed duty and unauthorised absence, and the company reserves the right to take action against you according to your conditions of service and the Employment Ordinance,” Yau said.

Cathay Dragon has suggested flight attendants seek independent legal advice to clarify their right to strike.

Tang said the health, risk and protection assessment, plus the economic and connectivity considerations meant he was disappointed by the call for strike action.

The airline’s cabin crews, among a number of voices, have called for the Hong Kong government to completely close all borders with the mainland to contain the spread of the highly infectious disease locally.

Under increased pressure to take action, the government has gradually shut down borders, leaving three open: the Hong Kong International Airport, Shenzhen Port, and the Hong Kong-Zhuhai-Macau Bridge.

“This is a critical time for our airlines,” Tang said. “In these challenging times, we have a responsibility to continue offering vital connections between Hong Kong and the rest of the world.

“Any such action would also be disruptive. We sincerely hope that the union will reconsider its position, in order to avoid any disruption to our operations … during this already challenging time for Hong Kong and our airline.”

The Hong Kong Dragon Airlines Flight Attendants Association said an all-out strike was necessary because once cabin crews report for duty, their destination can be changed, meaning a non-mainland flight could turn into one.

“It is all or nothing,” said Rebecca Sy On-na, the union’s chairwoman. “We are asking for a 100 per cent vote from cabin crew. We don’t want any chance that our members can still fly to mainland China ports.”

Cathay has begun reducing flights to the mainland by 90 per cent, modifying in-flight services to reduce crew exposure to passengers, cleaning aircraft cabins more thoroughly, and offering masks for all cabin crew.

On Wednesday it said it was reducing its worldwide flying by 30 per cent, while of the 22 mainland destinations serviced by the airline, all would be cut except Beijing, Shanghai, Chengdu and Xiamen.

The next day it announced a voluntary unpaid leave scheme for all 27,000 staff, who were strongly urged to take it.

Tang said action was needed because preserving cash was key and the airline’s current situation, faced with an outbreak that had sapped travel demand, was “just as grave” as the 2008 global financial crisis.

Sy compared the actions of the government with that of Cathay, who both only gradually shutdown borders and reduced Chins flights.

“Anytime there is a chance people can come from the mainland then there will be a chance for people to be infected, and the virus will spread right away,” she said.