Azerbaijan’s flag carrier has announced the suspension of flights to several Russian airports, citing potential flight safety risks following a crash of one of its planes that many experts have blamed on Russian air defense fire.

Surviving passengers said they heard loud bangs when the flight was approaching its original destination of Grozny in Russia

T hursday is an official day of mourning in Azerbaijan as an investigation is underway to determine what caused an airplane carrying 67 passengers to crash on Christmas Day in Kazakhstan, killing 38 and leaving at least 29 survivors. Video posted by CNN shows the plane crash-landing, exploding into a fireball and plumes of black smoke.