All 71 passengers and crew were killed when a Russian aircraft crashed after take off from Moscow.
The Saratov Airlines jet went down minutes after taking off from Domodedovo airport on Sunday afternoon.
Officials say they are considering weather conditions, human error and technical failure as possible causes, the BBC reported.
The Antonov An-148 was en route to Orsk in the Ural mountains.
It crashed near the village of Argunovo, about 50 miles south-east of Moscow. Wreckage was strewn over a large area.
Eyewitnesses told Russian media that the jet was on fire as it plummeted.
No emergency call was made from the aircraft. One of the flight recorders has been recovered.