A young Swiss International Air Lines flight attendant died a week after being exposed to smoke that filled the cabin and cockpit during a flight he was working, reports Business Insider.

The December 23 flight from Bucharest, Romania, to Zurich made an emergency diversion to Graz, in southern Austria, after engine problems spread smoke through the plane, the airline said in a press release.

The crew member, who has not been named publicly, was airlifted to a hospital in Graz, where he was in intensive care. He died on Monday.

"We stand with one another at this truly difficult time; and we will be doing our utmost, together with the relevant authorities, to determine the causes involved," Oliver Buchhofer, the airline's chief operating officer, said. "We have many questions, and we want them answered."