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.

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:

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.