What is known about a plane crash in Kazakhstan after Putin apologized for a "tragic incident"?

Russian President Vladimir Putin on Saturday apologized to his Azerbaijani counterpart for what he called a "tragic incident" following the crash of an Azerbaijani airliner in Kazakhstan that killed 38 people, but stopped short of acknowledging that Moscow was responsible.

Putin’s apology to President Ilham Aliyev came as allegations mounted that the plane had been shot down by Russian air defense systems attempting to fend off a Ukrainian drone strike near Grozny, the regional capital of the Russian republic of Chechnya, where the plane was heading.

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 Grozny in the North Caucasus on Wednesday when it was diverted. It crashed while trying to land near the city of Aktau, Kazakhstan, after flying hundreds of kilometers (miles) east across the Caspian Sea.

The plane went down near the coast about 3 kilometers (2 miles) from Aktau. Cellphone 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.

What have officials said about a possible cause?

Kazakhstani, Azerbaijani and Russian authorities say they are investigating the crash. Initial theories put forward by various officials included possibilities of a bird strike, bad weather and an oxygen canister exploding aboard the plane.

Embraer told The Associated Press in a statement that the company is “ready to assist all relevant authorities.”

Dmitry Yadrov, head of Russia’s civil aviation authority Rosaviatsia, said Friday that as the plane was preparing to land in Grozny in deep fog, Ukrainian drones were targeting the city, prompting authorities to close the area to air traffic.

Yadrov said that after the captain made two unsuccessful attempts to land, he was offered other airports but decided to fly to Aktau.

Later on Friday, senior officials in the U.S. and Azerbaijan made separate statements suggesting the plane may have been brought down by weapons fire, echoing those made by aviation experts who blamed the crash on Russian air defense systems responding to a Ukrainian attack.

Rashan Nabiyev, Azerbaijan's digital development and transportation minister, told Azerbaijani media that “preliminary conclusions by experts point at external impact,” as does witness testimony.

“The type of weapon used in the impact will be determined during the probe,” Nabiyev said.

White House national security spokesman John Kirby said that the U.S. has "seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defense systems,” but refused to elaborate, citing an ongoing investigation.

Those statements echoed assessments by outside aviation experts and raised pressure on Russia.

Why have some experts blamed Russian air defenses?

Some aviation experts have said the holes seen in the plane’s tail section after the crash indicate that it could have come under fire from Russian air defense 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 indicates a 90-99% probability that it was hit by a surface-to-air missile.

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-defense system.”

Osprey CEO Andrew Nicholson said that the company had issued more than 200 alerts regarding drone attacks and air defense systems in Russia since Moscow launched its full-scale invasion of Ukraine in February 2022.

FlightRadar24 said in an online post that the aircraft had faced “strong GPS jamming” that interfered with flight tracking data allowing it to monitor the plane's flight path. Russia has extensively used sophisticated jamming equipment to fend off drone attacks.

Yan Matveyev, an independent Russian military expert, noted on Thursday that the images of the crashed plane’s tail show damage compatible with shrapnel from the Russian Pantsyr-S1 air defense system.

It’s unclear why the pilots decided to fly 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 defense system and also had its systems affected by jamming equipment as it was approaching Grozny.

How did Russia's and Azerbaijan's leaders respond?

Putin on Saturday apologized to his Aliyev “for the fact that the tragic incident occurred in Russian airspace.”

An official Kremlin statement issued Saturday said that air defense systems were firing near Grozny airport as the airliner "repeatedly" attempted to land there on Wednesday, but did not explicitly say if one of them brought the plane down.

According to a readout of the call provided by Aliyev’s press office, the Azerbaijani leader told Putin that the plane was subjected to “external physical and technical interference,” although he also stopped short of explicitly blaming Russian air defenses.

Aliyev noted that the plane had multiple holes in its fuselage and that the occupants had sustained injuries “due to foreign particles penetrating the cabin mid-flight.”

Azerbaijan observed a nationwide day of mourning on Thursday. National flags were at half-staff, traffic across the country stopped at noon, and sirens were sounded from ships and trains.

Both Putin and Aliyev said Saturday that experts from Russia, Azerbaijan and Kazakhstan had begun probing the incident, and were launching inquiries in both Grozny and Aktau. Moscow has launched a criminal investigation into the crash.