A court has found four employees of Swiss air traffic control company Skyguide guilty of negligent homicide over a plane collision five years ago.
Three of eight defendants were handed suspended 12-month prison sentences on Tuesday, while a fourth was fined SFr13,500. The crash over southern Germany left 71 people, mostly children, dead.
Four other defendants were acquitted.
The agency was responsible for the airspace on July 1, 2002 when a Bashkirian Airlines plane collided with a DHL cargo jet near the town of Überlingen. The two cargo pilots and everyone on the passenger plane, including a large group of Russian schoolchildren on a holiday trip to Spain, were killed.
The eight defendants - middle managers, an air traffic controller and four technicians - were accused of negligent homicide. All had denied any wrongdoing, and four were finally cleared by the court.
Prosecutors had requested suspended prison sentences ranging from six to 15 months.
Handing down its verdict, the court in Bülach near Zurich said that the collision could have been avoided if two controllers had been on duty at the time.
Danish-born Peter Nielsen was the only air traffic controller on duty. Some of the defendants blamed him for not following proper procedures.
But prosecutors said a culture of negligence and lack of risk awareness at the air traffic control company contributed to the accident, and that it was not solely Nielsen’s fault.
Skyguide itself has only admitted partial responsibility for the accident, although its head did ask the family’s victims for forgiveness. The Swiss government also offered an official state apology to Russia.
The court blamed the three managers at the control centre for tolerating the single controller policy, which was incompatible with air safety rules.
Nielsen, who was stabbed to death in 2004 by a Russian man whose wife and children died in the crash, told investigators before his death that he had worked under stressful conditions on the night of the accident.
A colleague had taken a break and maintenance on the air traffic control system had affected monitoring and communications. The judges said that managers knew full well that the ongoing repairs would make the controller’s work more difficult.
The employee who was fined was a project leader overseeing the maintenance work.
The neighbouring control centres were not informed that the main telephone connection to Skyguide was out of order on the night of the incident. German officials tried to warn the controller of the collision risk, but could not reach him.
By the time Nielsen realised there was a problem, he gave the planes only 44 seconds warning that they were getting too close to each other. He also mistakenly told the Russian plane to descend - sending it straight into the cargo jet.
Skyguide took note of the court decision, but it did not seem to entirely agree with its findings.
"We are convinced that this tragedy is attributable primarily to systemic causes in the interplay between people, technology and procedures,” said its interim CEO Francis Schubert in a statement.
“Skyguide has learnt the lessons from this tragic event, and has done everything to ensure that an accident of this kind cannot happen again," he added.
In a 2004 report, German investigators said the accident was due largely to negligence on the part of Skyguide, and partially the fault of the two Russian pilots.
Immediately following the announcement of the verdict, some commentators in the Russian broadcast media criticised the sentences as too mild.
But one of the relatives of the victims welcomed the verdict. Vladimir Savchuk said the court decision should serve as a warning for others.
"It's not a punishment [for them] that we need, but a warning to others... so that their flight doesn't end in tragedy," Savchuk said on Russian state television.
swissinfo with agencies
A case of revenge
Vitaly Kaloyev, who lost his wife and two children in the Überlingen disaster, took revenge on Peter Nielsen by stabbing him to death at his home in Zurich in early 2004.
In October 2005, a Zurich court found the 50-year-old Russian architect guilty of the intentional killing of the controller and sentenced him to eight years in prison.
In August, the Federal Court overturned a decision to grant an early release of Kaloyev.
Skyguide is a non-profit-making limited company that is 99% owned by the Swiss government.
It is responsible for air traffic control in Switzerland and parts of neighbouring countries.
Skyguide is based in Geneva, but a new Air Navigation Service Centre in Zurich is expected to be fully operational next year.