The Airbus 320 was traveling from the Armenian capital, Yerevan, when it went down before it was to land in the Russian Black Sea resort of Sochi.
The deputy commercial director of the operator, the Armenian airline Armavia, said bad weather was the likely cause of the crash.
"As the airplane was approaching the Sochi airport, meteorological conditions worsened and the plane was sent back for another circle," Andrei Agadjanov said. "After that, the airplane disappeared from the radar screens."
Most of the passengers were Armenians. A Russian Foreign Ministry spokesman, Mikhail Kamynin, said there were also 26 Russian nationals on board.
Russian officials say 39 bodies have been recovered so far.
Both Russia and Armenia have declared May 5 a day of mourning.
Search and recovery efforts are continuing. The maker of the plane, Airbus, says it will also be sending experts to help with the crash investigation.
Some of the wreckage discovered so far lay some 400 meters below the surface.
(compiled from agency reports)