Russian criminal investigators are probing the qualifications of the crew involved in the fatal Saratov Airlines Antonov An-148 crash in Moscow, in order to establish whether the pilots had been properly trained.
The federal Investigative Committee is conducting its own analysis of the 11 February accident, and has declared "incorrect actions" of the crew to be the primary contributor to the crash.
Russia's Interstate Aviation Committee has already determined that the crew did not activate the pitot-static heating system before take-off, and subsequently lost control of the jet after receiving unreliable airspeed information.
As part of the criminal probe the Investigative Committee has been gathering evidence, conducting searches and seizures, and questioning instructors of the institutions where the pilots were trained in order to assess their qualification.
It states that this work includes efforts to "establish the legitimacy" of the certificates obtained by the first officer.
Saratov Airlines personnel are also being interviewed to determine whether there were violations of duty and rest periods for the crews.
Without waiting for the formal conclusions from the Interstate Aviation Committee, the Investigative Committee states that it is preparing a technical aviation judicial probe to take decisions on possible criminal activity.
None of the 65 passengers and six crew members survived the accident. The Investigative Committee says the inquiry has raised concerns over its thoroughness, regarding the collection of fragments and protection of the crash site.
Snow-covered ground had been among the obstacles facing investigators at the time of the accident.
Ground-penetrating radar has since been deployed to enable the probe to remove "all the material evidence, to the smallest pieces", says the Investigative Committee.