Angry and grieving Russian relatives watched today as a Swiss judge opened an emotionally charged trial by cross-examining air traffic controllers accused of helping to cause a rare and devastating mid-air collision.

The 71 dead included 49 children and teenagers on their way to a seaside holiday in Spain, a reward for good exam results.

The prosecutor is accusing eight members of the Swiss air traffic company Skyguide of manslaughter by neglect and is demanding suspended jail sentences of between six and 15 months. The accused men all plead not guilty.

“I want to know the truth,” Vladimir Savchuk said, before entering the improvised courtroom in Buelach, near Zurich. Mr Savchuk lost his wife, Irena, 38, who was supervising the children, as well as his daughter, Veronika, 14, and son, Vlad, 13. “I hope that all the guilty will be named and convicted. It has been almost five years since the crash: time for justice to be done.”

The crash happened in summer 2002 over the lakeside resort of Uberlingen, close to the Swiss border in southern Germany.

A German air accident inquiry in 2005 concluded that a catastrophic chain of events, sparked by human error, system failures and technical problems, had led to the crash.

A Bakhirian Airlines Tupolev carrying Russian schoolchildren from Moscow to Barcelona collided at 35,000ft with a DHL cargo jet flying from Italy to Belgium. The cargo jet, travelling at right angles to the passenger plane, sliced its fuselage in two. Everyone on board both aircraft was killed.

Judge Rainer Hohler witheld the names of the eight men in the dock, apparently to prevent them becoming targets of a revenge attack. The crucial figure in the tragedy, the air traffic controller Peter Nielsen, was knifed to death in front of his children three years ago by the father of one of the doomed Russian children. The Russian is currently serving a life sentence for murder in a Swiss prison.

Nielsen and another man, in the dock today, were in the control tower as the two aircraft crossed from Switzerland to Germany high above Lake Constance.

Nielsen’s companion went to lie down at about 11pm, assuming that it would be a quiet night, then two crises occurred simultaneously: in Friedrichshafen, a small airport across the lake in southern Germany, an aircraft made an unscheduled landing; and the Tupolev and the cargo jet unwittingly locked on to a collision course.

Nielsen raced between the two screens. A hotline phone to Friedrichshafen did not function and a back-up radar screen was defective. He was left with 43 seconds to warn the airborne aircraft.

The Russian pilot had already received instructions from his on-board computer to climb to avoid the cargo jet. Nielsen contradicted the mechanical order. The pilot chose to obey the human not the machine and smashed into the oncoming aircraft.

Prosecutor Bernhard Hecht, in his 23-page indictment, argues that some of the traffic control weaknesses could have been avoided by Skyguide, enough to have saved the passengers and crew. The two duty controllers should have been briefed about the defective machinery and Nielsen should never have been left alone.

“Was this due to cost-cutting measures?” Judge Hohler wanted to know today. A Skyguide executive said that he had no idea, but added that controllers were allowed to take breaks on quiet nights.

He emphasised that he considered himself innocent but, in an emotional outburst with a sidelong glance at the Russian relatives, he said: “It is still an unimaginable catstrophe for me. I cannot shake it off — I am terribly, terribly sorry.”

The trial is expected to continue for another two weeks.

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