CNN  —  Azerbaijan held a day of mourning on Thursday for the dozens of victims of an airliner crash in Kazakhstan, as questions were being asked over the cause of the disaster. The reasons why Azerbaijan Airlines flight J2-8243 came down are still unknown. Officials from Azerbaijan, Kazakhstan and Russia, three countries linked to the disaster, urged people not to speculate about the crash until investigations have concluded. The plane was traveling from the Azerbaijani capital Baku to Grozny