An Austrian Airlines Airbus A321-100, registration OE-LBC performing flight OS-125 from Vienna (Austria) to Frankfurt/Main (Germany) with 161 passengers and 6 crew, was in the initial climb out of Vienna's runway 29 when at about 2000 feet AGL the crew noticed a strong odour in the cockpit almost immediately followed by cabin crew reporting an acrid odour and smoke in the cabin and declared PAN. Both flight crew donned their oxygen masks, at least one cabin crew donned the smoke hood. The aircraft was vectored for a return to Vienna and landed safely on runway 34 about 15 minutes after departure. The aircraft stopped on the runway for inspection by emergency services, cabin crew reported there was no visible smoke anymore, the aircraft taxied to a remote apron, where passengers disembarked via stairs. There were no complaints by passengers about any health issue, the crew went to a hospital for precautionary checks after all passengers had disembarked.

The Aviation Herald received information that following the occurrence the left hand engine (CFM56) was immediately replaced.

On Nov 20th 2018 the airline reported the cause of the smell and light smoke was an engine detergent. The left engine had undergone specific maintenance, a compressor wash was subsequently conducted with the detergent to remove possible soiling from the compressor area. An engine run up was done, it appears however the detergent was more persistent and entered the air ducts.