A flight attendant aboard a Swiss aircraft that made an emergency landing in Austria last week due to smoke in the cabin has died, the airline said on Tuesday.

The flight from Bucharest to Zurich on December 23 was diverted to Graz after engine problems and smoke filled the cockpit and the cabin, Swiss International Air Lines said in a statement.

It said the attendant died on Monday in intensive care in the hospital in Graz. The attendant was one of two crew members who were hospitalised.

All 74 passengers aboard the Airbus A220-300 were evacuated after flight LX1885 landed safely, Swiss said.

“We are devastated at our dear colleague’s death,” Swiss Chief Executive Officer Jens Fehlinger said in the statement.

“His loss has left us all in the deepest shock and grief. Our thoughts are with his family, whose pain we cannot imagine. I offer them my heartfelt condolences on behalf of all of us at Swiss."

The public prosecutor's office in Graz has ordered a forensic examination of the attendant's body, Austria's APA news agency reported.

It has also appointed an aviation expert and initiated an investigation into the cause of the accident.

Following the incident, Swiss said it was also conducting an internal examination.

“We want to thoroughly clarify the causes of the smoke and the effects on passengers and crew,” the airline wrote on Thursday.

“The focus is on the mechanical parts of the aircraft, such as the engine, but also on the use of protective equipment for the cabin crew, known as Protective Breathing Equipment.” (AP)