Azerbaijan Airlines' Embraer 190 was en route from the 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 yet fully clear.
Aviation experts say an Azerbaijani airliner that crashed in Kazakhstan most likely went down after being hit by Russian air defence systems.
Here are some things to know about the crash that killed 38 out of the 67 people on board.
How did the plane crash?
Azerbaijan Airlines' Embraer 190 was en route from the 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 yet fully clear.
It crashed while trying to land in Aktau, Kazakhstan, after flying east across the Caspian Sea.
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The plane went down near the coast about three kilometres from Aktau.
Mobile phone footage circulating online appeared to show the aircraft making a steep descent before hitting the ground and exploding in a fireball.
Rescuers rushed 29 survivors to hospitals.
How did Azerbaijan react?
Azerbaijan observed a nationwide day of mourning on Thursday.
National flags were at half-mast, traffic across the country stopped at noon, and sirens were sounded from ships and trains.
Speaking at a news conference on Wednesday, Azerbaijani President Ilham Aliyev said that the weather had forced the plane to change from its planned course.
What do officials and experts say about a possible cause?
Kazakhstani, Azerbaijani and Russian authorities say they are investigating the crash.
Embraer told The Associated Press in a statement that the company is "ready to assist all relevant authorities".
Russia's civil aviation authority, Rosaviatsia, said that preliminary information indicated the pilots diverted to Aktau after a bird strike led to an emergency on board.
While officials remained tight-lipped, an Azerbaijani lawmaker directly pointed the finger at Russia.
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Rasim Musabekov told the Azerbaijani news agency Turan that the plane was fired upon in the skies over Grozny and urged Russia to offer an official apology.
Some aviation experts say the holes seen in the plane's tail section after the crash indicate that it could have come under fire from Russian air defence systems fending off a Ukrainian drone attack.
Mark Zee of OPSGroup, which monitors the world's airspace and airports for risks, said that the analysis of the fragments of the crashed plane indicate with a 90-99 per cent probability that it was hit by a surface-to-air missile.
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Osprey Flight Solutions, an aviation security firm based in the United Kingdom, warned its clients that the "Azerbaijan Airlines flight was likely shot down by a Russian military air-defence system".
Osprey CEO Andrew Nicholson said that the company had issued more than 200 alerts regarding drone attacks and air defence systems in Russia since the full-scale war in Ukraine began in February 2022.
FlightRadar24 said in an online post that the aircraft had faced "strong GPS jamming" that interfered with flight tracking data allowing to monitor planes' flight path.
Russia has extensively used sophisticated jamming equipment to fend off drone attacks.
A day later, no definitive word
Yan Matveyev, an independent Russian military expert, noted that the images of the crashed plane's tail show damage compatible with shrapnel from the Russian Pantsyr-S1 air defence system.
It's unclear why the pilots decided to fly hundreds of kilometres east across the Caspian Sea instead of trying to land in Russia after the plane was hit, he said, adding that they probably faced restrictions on landing at a closer venue and may have thought that the damage was not critical.
In Azerbaijan, Caliber online newspaper also claimed that the airliner was fired upon by a Russian Pantsyr-S air defence system and also had its systems affected by jamming equipment as it was approaching Grozny.
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The paper questioned why Russian authorities failed to close the airport despite the drone attack in the area on Wednesday, and why they didn't allow the plane to land in Grozny or other Russian airports nearby after it was hit.
Asked about the claims that the plane had been fired upon by air defence assets, Kremlin spokesman Dmitry Peskov told reporters on Thursday that "it would be wrong to make hypotheses before investigators make their verdict".
Officials in Kazakhstan and Azerbaijan have similarly avoided comment on a possible cause of the crash, saying it will be up to investigators to determine it.
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