Russian crash investigators have pointed to pilot error in the downing of the Kazan airliner which killed all 50 on board the Boeing 737.
According to flight recorders the pilots switched to manual control and pushed the steering column to pitch it into a nosedive in a correction to alter a second landing approach.
Both engines were running and no malfunctions were detected.
However critics of the Interstate Aviation Committee (IAC), which investigates air accidents in the former Soviet Union, have questioned its analyses pointing to inconsistencies.
In recent years the IAC’s conclusions following major accidents have almost invariably blamed the pilots.