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."

The Malaysian Airlines flight was travelling at cruising altitude over eastern Ukraine on a journey from Amsterdam to Kuala Lumpur when it was shot down in July 2014. A pro-Russian militia had misidentified the plane as a Ukrainian military transport aircraft.

In the crash’s aftermath, Azerbaijan has unleashed rare and stinging criticism of Russia, with the country’s president saying Moscow’s response has caused “surprise, regret and rightful indignation.”