Investigators in Russia say they cannot rule out the possibility that an attack downed a jet over the Black Sea, with the loss of all 92 passengers and crew.
An external “mechanical impact” could have caused Sunday’s disaster, a flight safety official said, while confirming there had been no explosion.
But he added that it was just one of many theories, including technical failure and human error.
The defence ministry airliner was bound for Syria at the time.
Russian media have published what they said was the pilots’ final conversation, reportedly transcribed from a flight recorder recovered from the wreckage.
It suggests that the Tu-154 jet’s wing flaps – panels which help lift an aircraft – were not moving together, causing the crew to lose control.
Analysis of the plane’s “black boxes” may not be completed until the end of January.
