One of 16 oxygen bottles for flight attendant use on a Cathay Dragon plane was found to have been depleted during a routine inspection following a flight from Kuala Lumpur to Hong Kong on Saturday.
All the cabin crew from that flight were suspended and two later dismissed, the airline said, adding that the police have been notified about the incident.
Cathay said the safety of passengers was not compromised at any time and the affected tank – which is meant for cabin crew use in emergency situations – was replaced prior to the plane’s next departure.
It was the latest in a series of tampering incidents to come to light involving the company’s aircraft in recent weeks, with dozens of staff suspended pending investigations.
Cathay has found itself embroiled in the extradition bill crisis, coming under fire from mainland media over some employees showing support for protesters.
Senior management have left the airline since the summer’s protests erupted, with some staff members sacked and passenger numbers plummeting.