Vitaly Kaloyev, who last week was ordered released by Switzerland's highest court, left a Zurich prison early Monday, said Alexander Gladkov, spokesman for the Russian embassy in Switzerland .
Kaloyev should return to Russia later in the day, Gladkov told The Associated Press.
The 51-year-old was convicted in October 2005 of premeditated homicide in the killing of Danish-born Peter Nielsen, an air traffic controller with Swiss company Skyguide.
Nielsen was the only person on duty when a Bashkirian Airlines plane and a DHL cargo jet collided on July 1, 2002 , in airspace he was responsible for over southern Germany. The crash killed 71 people, mostly schoolchildren on a holiday trip to Spain.
The sentence against Kaloyev, whose ordeal brought him widespread sympathy in his native Russia , was reduced to five-and-a-quarter years from eight years in July by a Swiss regional court, which ruled that he acted with diminished responsibility because of the deaths of his wife and two children.
The Swiss Federal Tribunal rejected an appeal last week by Zurich prosecutors against the reduction of Kaloyev's sentence. He was ordered released because he has served more than two-thirds of his sentence with good behavior.
Kaloyev has acknowledged that he must have killed Nielsen in February 2004, but said he could not remember the slaying.
Nielsen's family in Denmark was not reachable for comment after the court ruling. The family has kept a low profile since the killing.
In September, four Skyguide employees were found guilty of negligent homicide in a separate proceeding examining the events that led to the crash. Three midlevel managers were given one-year suspended prison sentences, while another employee - a project manager - received a suspended fine of 13,500 Swiss francs (US$11,200; EUR 8,250).
Four other Skyguide officials were acquitted of wrongdoing in the accident.