Azerbaijan on Thursday observed a nationwide day of mourning for the victims of the plane crash that killed 38 people and left all 29 survivors injured as speculation mounted about a possible cause of the disaster,

An Azerbaijan Airlines flight from Baku to the Chechnyan city of Grozny crashed Wednesday, killing 38. The plane flew hundreds of miles off its route and crashed on the wrong side of the Caspian Sea in Aktau,

Aviation experts say that Russian air defense fire was likely responsible for the Azerbaijani plane crash the day before that killed 38 people and left all 29 survivors injured

The Azerbaijan Airlines plane flew hundreds of miles off its scheduled route from Baku to Grozny, and crashed on the eastern shore of the Caspian Sea. Russia's aviation watchdog said a bird strike might have been the cause.

"No one claims that it was done on purpose," an Azerbaijan official told Reuters. They added their government "expects the Russian side to confess."

National flags were lowered across Azerbaijan, traffic across the country stopped at noon, and signals were sounded from ships and trains as the country observed a nationwide moment of silence.

The Azerbaijan Airlines Embraer 190 flight left Baku, Azerbaijan, on Christmas to Grozny, Russia. Instead, the plane crashed in Aktau, Kazakhstan.

A passenger plane flying from Azerbaijan to Russia with 67 people on board crashed in Kazakhstan Wednesday, authorities said.

There are early indications that a Russian anti-aircraft system may have struck the Azerbaijan Airlines plane that crashed in Kazakhstan, a U.S. official told ABC News.

At least 38 people were killed in an Azerbaijan Airlines crash that was likely caused by Russian antiaircraft fire, according to Ukraine and aviation experts. Photo: Azamat Sarsenbayev/Reuters

A U.S. official tells NBC News there are early indications that the passenger plane that crashed in Kazakhstan may have been hit by a Russian anti-aircraft system. The official said if it turns out to be the case,