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.

Azerbaijan Airlines flight J2-8243 caught fire as it tried to make an emergency landing in Aktau, southwestern Kazakhstan, on Wednesday. It was traveling from the Azeri capital Baku to Grozny, the capital of the Russian republic of Chechnya.

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.