An Azerbaijani airliner has crashed in Kazakhstan after being diverted, killing 38 of 67 people on board. Some things to know about the crash and the speculation about a possible cause: How did the plane crash?

Mobile phone footage circulating online appeared to show the Azerbaijani Airlines plane making a steep descent before slamming into the ground in a fireball in western Kazakhstan.

Russian aviation authorities said the Azerbaijan Airlines plane had hit a flock of birds. But some experts cast doubt on that account, pointing to footage showing apparent holes in the fuselage.