The probe into the Azerbaijan Airlines crash in Kazakhstan is examining the conduct of air traffic controllers after the aircraft encountered difficulty, a source said.

Several passenger plane crashes have occurred worldwide this year, including a Wednesday morning Azerbaijan Airlines wreck that has left dozens feared dead.

ASTANA – The International Air Transport Association (IATA) expressed condolences after the tragic crash of an Azerbaijan Airlines plane on Dec. 25 in Aktau and called for a thorough, impartial and transparent investigation.

Azerbaijan Airlines’ Embraer 190 was en route from Baku to the Russian city of Grozny when it was diverted for reasons yet unclear and crashed while making an attempt to land in Aktau in Kazakhstan.

"We can clearly say today that the plane was shot down by Russia," President Ilham Aliyev said in a televised statement

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.

Russian President Vladimir Putin apologized for the deadly Azerbaijan Airlines Flight 8243 crash on Christmas but did not take responsibility for causing it as an investigation continues into the matter.

Azerbaijan's president accused Russia of trying to cover up its role in a plane crash that killed 38 people. Preliminary results of Azerbaijan’s investigation into the crash indicated that a missile from a Russian air-defense system hit the aircraft.