Late on the night of July 1, 2002, two aircraft were flying at the same height, 36,000 feet, over southern Germany, in airspace controlled from Zurich by the Swiss company Skyguide. Bashkirian Airlines Flight 2937, a Tupolev Tu-154 flying from Moscow to Barcelona, carried 69 people — 60 passengers and nine crew. Most of the passengers were children: 46 of them were Russian schoolchildren from Ufa, in Bashkortostan, starting a holiday trip to Spain organised by the local UNESCO committee. Converging with them was DHL Flight 611, a Boeing 757 freighter flying from Bahrain by way of Bergamo, crewed by two pilots and carrying no one else.
A single controller, Peter Nielsen, was working the sector — alone at two workstations, his colleague resting, in a practice Skyguide’s management knew of and tolerated. Radar and telephone systems were degraded by maintenance, and the ground-based collision warning system was switched off. Nielsen recognised the conflict late and, about a minute before impact, ordered the Tupolev to descend. Seconds earlier, its TCAS collision-avoidance computer had ordered the crew to climb. The Russian crew obeyed the controller instead; the DHL crew obeyed their own TCAS, which also told them to descend. Both aircraft descended into each other, and at 11:35 p.m. they collided at about 34,900 feet over Überlingen, beside Lake Constance. All 71 people aboard the two aircraft were killed, 52 of them children.
Germany’s Federal Bureau of Aircraft Accident Investigation (BFU), in its report of May 2004, put the main cause on shortcomings in the Swiss air traffic control system: an understaffed night shift, maintenance that had disabled key safety systems, and a controller left to work two positions at once; Nielsen had also given the Tupolev crew the wrong position for the conflicting traffic. The report further identified the ambiguity then surrounding TCAS, which the Russian crew had been trained to treat as secondary to a controller’s instruction — and it drove the worldwide clarification that a TCAS resolution advisory must always be followed.
Skyguide at first blamed the Russian pilot, then accepted full responsibility and apologised to the families. On February 24, 2004, Peter Nielsen was stabbed to death at his home by Vitaly Kaloyev, a Russian architect whose wife and two children had died on Flight 2937; Kaloyev was convicted of intentional homicide in 2005 and released in 2007. In 2007 a Swiss court convicted four Skyguide employees of negligent homicide — three received suspended prison sentences and one was fined.
Near Brachenreute, where much of the Tupolev’s wreckage fell, stands the Broken Pearl Necklace memorial: a string of great wooden spheres, broken apart, raised in memory of the children of Bashkortostan and of both crews.
Download the BFU Investigation Report (4 MB file)