Kaloyev, a Russian engineer, lost his wife and two children when two aircraft collided over southern Germany in July 2002, killing 71 people. Eighteen months later he tracked down Peter Nielsen, 36, the air traffic controller he believed was responsible for the crash, and stabbed him to death in front of his family.
A court in Zurich found the 48-year-old Russian guilty of premeditated killing. Under Swiss law, premeditated killing ranks between murder and manslaughter, with a maximum sentence of 20 years. Kaloyev has already served 600 days in jail.
"This is an extremely mild sentence and I will seriously consider appealing," Zurich's chief prosecutor said. "I cannot be content with eight years." He had wanted 12 years.
Kaloyev agreed the evidence indicated he "probably had" killed Mr Nielsen, but he claimed he could not remember the attack. On Tuesday, he said repeatedly he had not intended to kill anyone, saying all he wanted was an apology. The native of North Ossetia refused to stand for the verdict yesterday and said before he was led away: "I have forgotten how to live."
As he left, he turned and smiled and waved at his supporters who packed the room, including North Ossetia's president.
Throughout his two-day trial, Kaloyev looked at photographs of his smiling 10-year-old son, four-year-old daughter, and wife who were killed in the crash. He said he felt pity for Mr Nielsen's three children
Although psychiatric reports suggested he was responsible for his actions, defence lawyers had sought a three-year sentence for manslaughter, claiming Kaloyev was suffering an emotional blackout when he stabbed Mr Nielsen. But judges dismissed the plea.
Kaloyev's world collapsed in July 2002 when a Bashkirian Airlines Tupolev 154 carrying his wife and two children collided in mid-air with a DHL Boeing cargo plane over the German town of Überlingen.
Mr Neilsen, a Dane who worked for the Swiss aircraft monitoring company Skyguide, was alone on duty at Zurich air traffic control at the time. He was responsible for guiding the aircraft through Swiss-controlled air space.
Investigators found Mr Nielsen had not been told that the collision avoidance system was not fully working that night. But he did manage to warn the pilots they were on a collision course only 43 seconds before the two aircraft smashed into each other.
The accident caused outrage in Russia after the Swiss authorities appeared to cover up staff and technical problems at Skyguide and blamed Russian pilots for the accident.
A total of 45 children died in what was Germany's worst civilian air disaster. Most of the children were on their way to Spain for a holiday. The wreckage was spread over an area covering 35 square kilometres.
Kaloyev, who was working on a building contract in Spain at the time, took the next available flight to Germany and was the first relative at the scene.
He found the body of his four-year-old daughter, Diana, virtually unscathed as her fall from 36,000 feet had been broken by trees. "She was carried to earth by an angel," Kaloyev said at the time. The mangled corpse of his son, Konstantin, was on Tarmac in front of a bus shelter and the barely recognisable body of his wife Svetlana, 42, was found days later in a field of maize. "I cannot live any more," Kaloyev said then. "I simply exist."
After the tragedy, Kaloyev stopped work, refused to shave and constantly wore black. He turned the family home in the Caucasian town of Vladikavkas into a shrine dedicated to his dead wife and children. Photographs show their beds covered with children's dolls, a schoolboy's chessboard, and boxes of his wife's favourite scent. The engineer used his life savings to pay for an elaborate tombstone displaying portraits of his family.
State prosecutors said Kaloyev began to think of seeking revenge for the deaths the year after when he attended a memorial service in Überlingen and became incensed because Skyguide was accepting only partial responsibility for the crash.
The engineer hired a Russian detective who traced Mr Nielsen. On 24 February last year, Kaloyev, still dressed in black and clutching photographs of his wife and two children, turned up at the air traffic controller's home outside in Zurich and rang the bell. Mr Nielsen opened the door. There was a short argument before Kaloyev pulled out a Swiss-made "Ranger" knife and stabbed his victim repeatedly in the chest.
Yesterday Kaloyev told the court his bundle of photographs had fallen to the ground and had made him feel as if his children were being "thrown around in their coffins". He said he was overcome by rage and could not remember what happened after that.
Mr Neilsen died from his wounds within minutes later as his three children watched him helplessly.
"I went to Nielsen as a father who loves his children so he could see the photos of my dead children and next to them his kids, who were alive," Kaloyev told the court.
Prosecutors in Germany and Switzerland are continuing investigations against Skyguide staff in an attempt to establish whether they can be prosecuted for negligence. Skyguide has accepted full responsibility for the crash and asked relatives of the victims for forgiveness.