Kaloev, 49, is still kept under observation in the psychiatric clinic of Reinau, Zurich canton, although the psychiatric examination had confirmed his being of sound mind.
Another, most probably the last, interrogation will be held in mid-February, the Swiss news agency said on Friday.
After it the case will be referred to the court. Kaloev may be accused of homicide, first- or second-degree murder, heat of passion homicide. Investigators do not know to this day when Kaloev could buy the crime weapon - 22-cenitimeter knife - but are certain that it was bought in Switzerland.
On the night of February 24, 2004, Peter Nielsen, 36, who was on duty at the Skyguard panel when the air crash happened above the Bodensee, was killed near his home in Kloten. Kaloev admits that on that day he had come to the AT controller's house to show him the photos of his wife and children but Nielsen accidentally pushed him off and the pictures fell to the ground. Kaloev lost control of himself and did not remember what followed.
Kaloev's entire family - wife, daughter and son - died in that air crash. He was arrested in a Kloten hotel the day after the murder.
On the night between July 1 and 2, 2002, the crash of the Tu-154 of the Bashkir Airlines company and the Boeing transport killed 69 passengers of the former (mostly Bashkir children flying for summer vocation to Spain) and two Boeing pilots.
The catastrophe happened in the Skyguard zone of responsibility. The German Aircrash Investigation Agency laid most of the blame on Skyguard and in part on the two pilots of the Russian jetliner.
