It was a tense conversation between two authoritarian leaders used to their own way.

Russian President Vladimir V. Putin offered explanations for the crash of the Azerbaijan Airlines plane that killed 38 people a day earlier. Maybe it was a flock of birds, said Mr. Putin, or an exploding gas tank. Maybe a Ukrainian drone.

But Azerbaijan President Ilham Aliyev wasn’t buying it, according to two people familiar with the late December phone call. Hours after the crash, it became clear that the plane had been shot down by Russian air defenses, in what appeared to be a fatal mistake. It left shrapnel lodged in a passenger’s leg and punctured the plane’s fuselage with holes.

On December 29, Mr. Aliyev went public with his anger without mentioning the Russian president by name. “Attempts to deny the obvious facts,” he said, “are both senseless and absurd.”

The people who described the phone call insisted on anonymity to discuss the sensitive diplomatic communication. The Kremlin did not respond to a request for comment.

Anger over the plane crash – and the willingness of Mr. Aliyev to challenge Mr. Putin in public – revealed an incredible rift between the two post-Soviet rulers who had grown closer during more than two decades in power. Mr. Putin tried to engage Mr. Aliyev in an obvious effort to cover up the cause of the accident; Mr. Aliyev, emboldened by Russia’s waning influence in countries it once dominated, insisted that Russia publicly acknowledge its guilt.

Interviews with Azerbaijani officials and people close to the government last week showed how the Dec. 25 crash of an Embraer 190, with 67 people aboard, became a geopolitical turning point for the former Soviet Union. Instead of allowing Mr. Putin to dictate his response to the tragedy, Mr. Aliyev repeatedly attacked Russia for its failure to accept responsibility.

Rasim Musabekov, a member of Azerbaijan’s parliament’s foreign affairs committee, described Russia’s response to the crash as an “absurd stance.”

“Azerbaijan will not accept such a chauvinistic attitude,” he added.

Behind the scenes, interviews showed, these tensions flared directly between Mr. Aliev and Mr. Putin, although the two autocrats often found a common language. In a call on Dec. 28 and another the next day, people familiar with the calls said, Mr. Putin invited Mr. Aliyev to agree to have the aviation authority based in Moscow investigate the accident. Mr. Aliyev refused, insisting that the plane’s black boxes be deciphered in Brazil, where the jet was made, in a clear sign of distrust for the Russian leader.

Officials in Azerbaijan’s capital, Baku, arranged interviews with The New York Times with three survivors, who said it became clear to some passengers they were under attack immediately after at least two explosions rocked the plane in midair.

After the second explosion, the girl started screaming. Leyla Omarova, 28, looked across the aisle from her window seat and saw the girl’s tights stained with blood.

Three rows behind them, Nurullah Sirajov, 71, was trying to comfort his wife. He told her that the first bang must have been the impact of the landing gear. They had never flown before.

Then came a second explosion, a gust of wind from the back of the plane and shouts, he said, from other passengers: “We’ve been hit.”

As the jet jerked up and down, approaching the Caspian Sea to within 100 feet, Mr. Sirajov thought that at least his and his wife’s marital quarrels over who would die first would finally be resolved: they would die together. But after the front of the plane disintegrated on impact, the tail broke off, tipped over and slid hundreds of meters through the sandy ground.

“Is anyone alive?” Mr. Sirajov remembers shouting into the sudden silence as he hung upside down from the harness.

With Europe closing its airspace to Russia after Putin’s invasion of Ukraine, many Russians flying west now connect in Azerbaijan, an oil- and gas-rich former Soviet republic of 10 million people sandwiched between Russia and Iran. Russia also sees Azerbaijan as a key link in the expanded the trade route to the south to Iran, India and the Persian Gulf.

Its role as a transit point for sanctions-ridden Russia is just one way Azerbaijan has seen its influence over its much larger northern neighbor grow. Mr. Aliyev has also used Russian military distraction in Ukraine to push Russian peacekeeping troops out of Nagorno-Karabakh, an Armenian-controlled enclave that was retaken by Azerbaijan in 2023.

Mr. Aliyev strengthened his country’s alliance with Turkey and armed Azerbaijan with high-tech weapons bought from Israel. He achieved a fierce crackdown on activists and independent journalistsbut it has maintained its relationship with Europe, which Azerbaijan sees as a key alternative to Russian oil and gas.

Farhad Mammadov, a political analyst from Baku, said that Russian political and economic “leverages of pressure” on Azerbaijan have been reduced to “practically nothing”. Aykhan Hajizada, a spokesman for Azerbaijan’s Ministry of Foreign Affairs, was outspoken about his country’s influence over Russia: “They don’t want to lose Azerbaijan as well,” he said.

The uproar over the plane crash appeared as a test case. A senior US diplomat, who spoke on condition of anonymity because he was not authorized to comment publicly, described the aftermath of the crash as a “proof of concept” of Azerbaijan’s ability to stand up for itself. Other post-Soviet countries that have also sought a more direct relationship with Russia, such as Kazakhstan, are watching closely.

“If you behave like this in this incident with Azerbaijan, then what will the Uzbeks, Kazakhs and other remaining partners of Russia think of you?” – asked parliament member Mr. Musabekov. “Russia, as a country, is a very, very toxic partner with whom you need to minimize relations.”

Mr. Aliyev, who studied in Moscow and took over as ruler of Azerbaijan from his father in 2003, learned of the accident while on his way to a summit of post-Soviet leaders in St. Petersburg. Petersburg. He called Mr. Putin from the plane to tell him that he would not be coming.

Hours later, Azerbaijani officials landed in Aktau, Kazakhstan, the airport where the Embraer 190 attempted to make an emergency landing. At the nearby crash site, officials immediately realized that the theories they had heard from Russia about a bird strike or an exploding oxygen tank were wrong.

“When I saw the aircraft, it was full of holes,” Rinat Huseynov, director of security for Azerbaijan Airlines, said in an interview. “We didn’t imagine this was even possible.”

Mr. Aliyev and Mr. Putin spoke again twice in the days after the accident. Mr Putin apologized for the “tragic incident” in Russian airspace, but did not admit that Russia shot down the plane. The day after the apology, December 29, Mr. Aliyev went public and accused Russia of a cover-up.

“Unfortunately, the first three days we heard nothing from Russia except some absurd theories,” Mr. Aliyev he said.

Officials said they expect preliminary findings from the investigation by the end of January. Mr Aliyev reiterated last week that Russia must accept responsibility and pay compensation, while the Kremlin said it was cooperating with the investigation.

“We are interested in an absolutely objective and impartial investigation,” Dmitri S. Peskov, Putin’s spokesman, told reporters last week.

The working theory of the Azerbaijanis is that shrapnel from explosive missiles from the Russian Pantsir air defense system damaged the plane. Metal fragments as long as four inches were found at the crash site.

Flight data and cockpit voice recorders, officials said, could help explain why the pilots chose to cross the Caspian Sea to land in Kazakhstan rather than a nearby airport in Russia; Mr Huseynov, director of air transport security, said the decision seemed logical given the cloudy conditions in southern Russia at the time.

Inside the passenger cabin, the flight attendants tried to calm the panic. Ms. Omarova, on her way to see family in Russia, said she lost consciousness. Mr. Sirajov, who was packing New Year’s gifts for his grandchildren in Grozny, said the only thing on his mind was comforting his wife.

Flight information shows that after crossing the Caspian Lake, more than an hour after the pilots reported what they thought was a bird strike, the plane crashed on its second attempt to land at Aktau Airport. All the survivors were seated roughly in the back third of the plane, according to a person close to the investigation.

After the last part stopped, Mr. Sirajov fumbled in the dark to unbuckle his seatbelt, unable to tell what had happened to his wife. Only later did he find out that she had also survived.

Finally, Mr. Sirajov unbuckled his seat belt and threw himself onto the ceiling of the cabin. “Go that way, go that way,” he remembers as someone pushed him towards a glimmer of light.