On Christmas Day, a plane traveling from Baku, Azerbaijan, to Grozny, Russia, crashed in Kazakhstan, killing over half of its passengers. Theories abound regarding why the plane made an emergency landing near the Kazakhstani city of Aktau.

An Azerbaijani airliner has crashed in Kazakhstan after being diverted, killing 38 of 67 people on board. Some experts alleged that the plane went down after being hit by Russian air defense systems. Some things to know about the crash and the speculation about a possible cause:

U.S. officials say Russia could be behind a passenger plane crash in Kazakhstan that left at least 38 dead Wednesday, but Russia is denying any involvement.