As authorities in several countries tried to determine what caused the deadly crash of a passenger airplane in Kazakhstan, investigators and experts Thursday were focusing on the possibility that a Russian air defense system had struck the plane.

Russian air defenses, rather than a bird strike, likely caused the downing of an Azerbaijan Airlines flight, killing 38 people.

An Azerbaijan Airlines plane with dozens on board flying from the Kazakh capital, Baku, to Grozny in Russia crashed in western Kazakhstan, officials said.

The survivability of a plane crash largely depends on the circumstances of the accident. However, statistics show that rear seats can be among the safest.

After an Azerbaijan Airlines jet crashed in Kazakhstan, speculation mounted about why the plane went down and whether possible Russian air defense action may have played a role.