Iran shot down plane with two Russian-made missiles, US official says

Ukrainian President Volodymyr Zelensky talked to UK Prime Minister Boris Johnson Thursday, expressing condolences over the three British citizens who died in the crash.

"Ukraine is grateful for the UK's comprehensive support. Looking forward to stepping up our bilateral cooperation & to visiting London on invitation of Boris Johnson," Zelensky added.

He also spoke to Afghanistan President Mohammad Ashraf Ghani, saying he would "provide all information about the results of the investigation to the Afghan authorities."

According to a statement, Zelensky sent condolences over the death of four Afghan citizens in the plane crash.

“Ukraine sincerely shares the grief of the families of the dead. Truth is most important to us,” he added.

Investigators are scrambling to determine the cause of the crash that killed all 176 people on board a plane that came down shortly after takeoff from Tehran.

The Boeing 737 jet, operated by Ukraine International Airlines, took off early on Wednesday en route to the Ukrainian capital Kiev and disappeared from radar minutes later.

Eighty-two Iranians, 63 Canadians, and 11 Ukrainians died in the crash, which took place between the cities of Parand and Shahriar.

There were also 10 Swedes, four Afghans, three Germans and three British nationals among the victims.

There have been numerous questions around the fate of the black boxes recovered from the Ukraine International Airlines Boeing 737, which crashed outside Tehran.

If a country where a crash took place did not have the technology to analyze data, the black box would instead be sent to places that have extensive experience and tools to read raw flight data -- such as the UK, US, France and Australia.

What we don't know is whether Iran has the technology to do that. If not, Iran may need to decide where to send the two recovered boxes.

What would be devastating is if it botched an attempt to read the boxes; in the worst case scenario this could destroy the data.

The boxes could be sent to Russia which has the means to read black box data.

Ukrainian President Volodymyr Zelensky rang Swedish Prime Minister Stefan Löfven to express his condolences to the loved ones of the 10 Swedish citizens killed in the plane crash in Iran. 

“Ukraine is stunned by the tragedy. Thank you for your solidarity and empathy,” Zelensky said in the phone conversation, according to a Thursday statement.

Zelensky also invited Sweden to join the investigation.

Löfven also expressed his condolences from the people of Sweden and said that officials in Stockholm were ready to assist, using all possible means to ensure a transparent investigation.

Zelensky stressed that Ukraine was in constant contact with a group of experts in Tehran and would inform its partners of the progress of the investigation.

It's the second day of investigation into Wednesday's Ukraine International Airlines plane crash, which killed all 176 people on board when the Boeing 737 plunged to the ground just after takeoff from Tehran.

Questions on what caused the tragic incident loom large. Here are some of them:

Why did the plane crash?

There have been conflicting reasons given for the tragedy, and Ukrainian authorities have signaled that an answer will only be provided after a full investigation has been made.

By Thursday, the Iranian Civil Aviation Organization released a preliminary report that said the plane was on fire before it crashed, citing witnesses. It added that the aircraft changed direction after a problem and turned back toward the airport.

Now, Ukraine says multiple possible theories are being discussed with Iranian investigators: including the plane being hit by an anti-aircraft missile, a collision, technical failure or a terrorist act.

Is it linked to Boeing's ongoing technical problems?

The plane is a Boeing 737-800, a predecessor to the company's 737 Max, which has been grounded since March after its involvement in two fatal crashes that killed 346 people.

But the 800 version of the jet, also known as a 737 Next Generation or NG, has had its own problems.

All of this could add to the crisis Boeing has been grappling with over the different jet, the 737 Max, but there has been no indication yet that this is a manufacturing issue.

What will happen to the black box?

A plane's so-called "black boxes" -- the flight data and cockpit voice recorders -- can provide crucial evidence about what happened before a crash.

Iran’s Civil Aviation Organization head, Ali Abedzadeh, said it would not hand the flight data recorders to Boeing or the United States after they were found on Wednesday.

What is unclear is whether that decision was to do with hostilities between Tehran and Washington, which escalated after a US strike that killed Iran's top commander, Qasem Soleimani, on Iraqi soil last week.

The move was not necessarily against protocol, former US FAA chief of staff Michael Goldfarb told CNN Wednesday.

Under international rules, Iran would be the lead investigator of the crash and Ukraine should participate as the state of registry and state of operator of the aircraft.

But the US -- where the Boeing jet was designed and manufactured -- is not required to be involved in investigations right off the bat, Goldfarb said.

But Goldfarb added there was no way the Iranians could refuse to work with Boeing and do justice to the investigation.

"They have to work with Boeing. Boeing has all the data, owns all the drawings and designs, they have the engineers, they know the plane."

This does not mean there has been no global cooperation. Canada and Sweden were invited to join the investigation on Thursday by Iranian and Ukrainian experts.

Canadian and Swedish authorities have been invited to cooperate in the investigation into Wednesday's crash, the Iranian Civil Aviation Organization said in a statement.

The first joint meeting between Iranian and Ukrainian experts, sent to Tehran to investigate the incident, has already taken place, according to the organization.

No further details were provided. 

This comes as Ukraine said it is probing multiple possible causes of the crash. The head of its national security and defense council said these were raised at Thursday's meeting.

The causes under investigation include the airliner being hit by an anti-aircraft missile, a collision, technical failure and a terrorist act.

A steady stream of mourners have been leaving flowers and tea lights at the arrivals hall at Boryspil International Airport, in the Ukrainian capital Kiev, a day after 176 people died in the plane crash in Iran.

Eleven Ukrainians were killed, many of whom were crew members on the Ukraine International Airlines flight.

Olena, who declined to give her surname, told CNN that she had come to the airport to pay tribute to her friend and former classmate, Serhii Khomenko -- one of the pilots onboard the Boeing 737 aircraft. They had attended school together in the northern Russian city of Murmansk.

Visibly upset by the death of her friend, Olena said Khomenko has left behind a wife and two children, adding that he was an avid boxer.

Valeriy, who also declined to give another name, told CNN that his sister is godmother to the children of the flight's instructor pilot Oleksiy Naumkin.

Holding back tears, Valeriy told CNN that Naumkin was an experienced pilot who "was so funny and liked to joke."

Valeriy said he last saw his friend a couple months ago, adding that he was shell-shocked when he heard the news.

Ukraine is investigating multiple possible causes of Wednesday's deadly jetliner crash that killed 176 passengers and crew shortly after takeoff in Tehran. 

Ukraine’s National Security and Defence council chief, Oleksiy Danilov, wrote on Facebook that a meeting is taking place Thursday with Iranian authorities, where various causes behind the crash are "being studied."

These include the theory that the plane was hit by an anti-aircraft missile, Danilov wrote.

It's still not clear what caused the crash and several explanations, including technical failure, have not been ruled out.

Other theories under consideration are whether the plane collided with a drone or “other flying object”; technical problems with the plane’s engine causing it to explode, or finally whether an explosion inside the plane was a terrorist act.

Twenty minutes before the plane took off from the Iranian capital, Sheyda Shadkhoo called her husband from aboard the flight. She wanted him to reassure her that everything would be fine, he says.

She'd taken three weeks off from her job in Toronto to visit her mother and sisters in Tehran. Her vacation was over, and she was heading back to Canada to her husband, Hassan Shadkhoo. Her flight was leaving from Tehran to the Ukrainian capital of Kiev.

"I spoke to her ... 20 minutes before the plane took off," he said Wednesday in Toronto. She was worried about the tensions between Tehran and the United States after President Donald Trump ordered the killing of Iranian top general Qasem Soleimani.

"She wanted me to assure her that there wasn't going to be a war. I told her not to worry. Nothing's gonna happen," her husband told CNN's news partner CBC. Then she said goodbye and turned her phone off in preparation for takeoff.

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