Azerbaijan Airlines’ Embraer 190 was en route from Azerbaijani capital of Baku to the Russian city of Grozny in the North Caucasus on Wednesday when it was diverted for reasons that aren’t fully clear yet. It crashed while making an attempt to land in Aktau, Kazakhstan, after flying east across the Caspian Sea.

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.

The cause of the Azerbaijan Airlines tragedy is under investigation, but the company is crediting “the crew's valiant dedication to their duties until the last moment”