On 1 July 2002, Bashkirian Airlines Flight 2937, a Tupolev Tu-154 passenger jet with 69 people on board and DHL Flight 611, a Boeing 757 cargo jet with a crew of two, collided over the towns of Überlingen and Owingen, in southern Germany. All 71 people on board both aircraft were killed.
The official investigation by the German BFU identified as the main cause of the collision a number of shortcomings on the part of the Swiss air traffic control service in charge of the sector involved, and also ambiguities in the procedures regarding the use of TCAS, the on-board aircraft collision avoidance system.[BFU 2]
Less than two years after the crash, on 24 February 2004, Peter Nielsen, the air traffic controller on duty at the time of the collision, was murdered in an apparent act of revenge by Vitaly Kaloyev, a Russian citizen who had lost his wife and two children in the accident