During the flight from Hamburg to Gran Canaria (Spain), a strong odour developed inside the aircraft during the landing approach to Las Palmas. As the co-pilot noticed symptoms himself, he put on his oxygen mask. Three members of the cabin crew also felt strongly affected. The subsequent landing was uneventful. During the preparations for the return flight and before boarding, a run-up of the engines was carried out, during which the cabin crew were supposed to be at their stations. When the APU bleed air was switched on, the flight attendants again noticed an odour in the cabin. Due to the symptoms, two flight attendants and the co-pilot were taken to hospital. One crew member was hospitalised for further diagnosis/treatment after being transported back to Hamburg. Causes and contributing factors The investigation into this event revealed circumstantial evidence suggesting that several crewmembers were affected by contaminated cabin air that was being supplied by the aircraft?s air conditioning system. After several tests and analyses have been carried out till this day, the investigation yielded no conclusive findings as to the possible source of the contamination or the hypothetical toxic compound involved.