
Justin Trudeau has today vowed to get answers after 176 people including 63 Canadians died in a plane crash near Tehran, with Iran blaming an engine fire but refusing to hand over the recovered black boxes.

The Boeing 737 jet came down just minutes after take-off from Imam Khomeini International Airport early this morning, sparking fresh alarm in the Middle East hours after Iran launched missile strikes on US bases.

Three Britons and 63 Canadians were among the 168 passengers and nine crew on board the Ukrainian International Airlines flight to Kyiv. There were no survivors.

Today the Canadian PM offered his 'deepest condolences' to the victims' families and vowed to 'ensure that this crash is thoroughly investigated, and that Canadians' questions are answered'. The US promised 'complete co-operation' with the probe.

But the initial assessment of Western intelligence agencies is that the Ukrainian airliner was not brought down by a missile, according to a Canadian security source.

The source, who declined to be identified, said the agencies believed the Boeing 737 plane suffered a technical malfunction.

Iran has pointed the finger at 'technical difficulties' and says the pilot lost control after an engine caught fire in mid-air, but Tehran is refusing to say what will happen to the black boxes.

Video footage appeared to show the plane already burning before it fell out of the night sky, while pictures at the crash site showed the fuselage peppered with mysterious holes.

The Boeing plane was less than four years old and had been checked just two days earlier, with 'one of our best crews' manning the aircraft, the Ukrainian airline said.

The disaster will heap further pressure on Boeing which was thrown into crisis by two plane crashes in October 2018 and March 2019 which killed a combined 346 people - especially if Iran's claims are proved true.

People stand near the wreckage after a Ukrainian plane carrying 176 passengers crashed near Imam Khomeini airport in Tehran, sparking fresh alarm in the Middle East today

Pieces of debris are seen lying at the crash site in a picture released by an Iranian news agency today, showing what appeared to be holes in the fuselage of the Boeing aircraft

Rescue workers in protective suits gather up the bodies of passengers who were killed in the Boeing 737 crash in Iran today

The black boxes (pictured) from the Ukrainian airliner were found today but Iran says it will not hand them over to Boeing

An aerial view of the crash site where rescuers searched the debris this morning with the cause of the crash still unclear

A map showing the route of the brief flight and some of the clues to the cause of the crash which soon started to emerge

A woman shows her emotions at Boryspil International Airport in Kyiv where the doomed plane was headed

Victims of the Ukraine International Airlines crash in Iran, University of Alberta professors Mojgan Daneshmand and Pedram Mousavi, pose with their daughters Daria and Dorina Mousavi

A victim of the Ukraine International Airlines crash in Iran, Dr. Parisa Eghbalian (left) poses with her husband Dr. Hamed Esmaeilion at their dentistry practice in Aurora, Ontario, Canada. Dr. Eghbalian died in the crash along with her daughter Reera Esmaeilion, nine. Her husband Dr. Esmaeilion is now en route to Tehran

French jet engine manufacturer CFM said any speculation about a technical failure was 'premature', while the Ukrainian embassy in Iran initially ruled out a missile strike but later backtracked.

Aviation experts were at odds today as they struggled to explain the disaster, with some saying a shoot-down was unlikely while others said an MH17-style event should be the starting assumption.

The crash sparked fresh fears in the Middle East, which is on high alert after Qassem Soleimani was killed last Friday, and a series of airlines have today announced they will stop flying over Iranian airspace.

The Ukrainian foreign ministry revealed there were 82 Iranians, 63 Canadians and three Britons on flight PS752, along with 11 Ukrainians, 10 Swedes, four Afghans and four Germans.

The three British victims were later named as businessman Mohammad Reza Kadkhoda-Zadeh, 40, and engineers Saeed Tahmasebi Khademsadi, 35, and Sam Zokaei, 42.

Canada is home to a large Iranian diaspora community and UIA offers discount flights between Tehran and Toronto, with a transit in Kiev.

Today Boeing declared the air disaster a 'tragic event' and offered its 'heartfelt thoughts' to the 176 passengers and crew on board the plane.

'We are ready to assist in any way needed,' the airline said in a statement.

The jet which crashed was a Boeing 737-800 - a very common single-aisle, twin-engine jetliner used for short to medium-range flights. Thousands of the planes are used by airlines around the world.

Introduced in the late 1990s, it is an older model than the Boeing 737 MAX, which has been grounded for nearly 10 months following the two deadly crashes in Indonesia and Ethiopia.

According to flight tracking data from FlightRadar24, the jet which crashed today reached an altitude of 7,925ft before tracking suddenly ended after three minutes.

The plane had been delayed from taking off from Imam Khomeini International Airport in Tehran by almost an hour.

Unverified video appeared to show Ukrainian plane ablaze as it falls from the sky before crashing huge fireball

Mojgan Daneshmand and Pedram Mousavi, pose with their daughters Daria and Dorina Mousavi in an undated family photo in Edmonton, Alberta

A fleet of search and rescue workers at the crash site today after a Boeing 737 crashed near Tehran, sparking fresh alarm in the Middle East

Canadian prime minister Justin Trudeau (pictured) offered his 'deepest condolences' to the victims' families and vowed to 'ensure that this crash is thoroughly investigated, and that Canadians' questions are answered'

The three British victims: dry cleaning firm owner Mohammad Reza Kadkhoda-Zadeh (left), newlywed engineer Saeed Tahmasebi Khademsadi (centre) and BP engineer Sam Zokaei (right)

One of the engines of the plane lies among the wreckage - as its French manufacturer said it was too early to say what caused the crash

Debris at the crash site included English-language books, amid reports that Canadians and Britons were killed in the crash

Part of the Ukrainian Airlines jet lies at the crash site today where rescue workers are recovering more than 170 bodies

Rescue workers in masks retrieve the bodies of passengers from the crash site following the fatal crash near Tehran today

Iranian state media reported the Kiev-bound Ukrainian International Airlines flight PS752 - Boeing 737 -crashed in the early hours of Wednesday morning just three minutes after takeoff from Imam Khomeini International Airport, killing all 167 passengers and nine crew on board

Part of the wreckage from Ukraine International Airlines flight PS752, a Boeing 737-800 plane that crashed after taking off from Tehran's Imam Khomeini airport on January 8

An image from the flight tracker website Flightradar24 showing the path of the Ukranian International Airlines jet which crashed just over two minutes after taking off from Tehran

President Donald Trump says 'all is well' and 'so far so good' as the damage and casualties continue to be assessed after Iran fired more than a dozen ballistic missiles at two Iraqi bases housing American troops

Boeing's safety record: Explosive decompression, mid-air collisions and some of the worst crashes in history Today's crash will pile further pressure on Boeing after two deadly crashes in five months forced the 737 Max 8 aircraft to be grounded worldwide. All 189 people on board a Lion Air flight in Indonesia were killed when the 737 Max 8 jet dived into the sea in October 20108. Five months later in March 2019, 157 passengers and crew were killed when an Ethiopian Airlines plane - another of the Boeing jets - crashed shortly after leaving Addis Ababa. A number of other 737 Next Generation aircraft have also been involved in deadly accidents over the years. September 29, 2006 - There were no survivors when a Gol Transportes Aereos Flight 1907, using a brand new 737-800, collided with another jet in mid-air and split apart, dropping in the Brazilian jungle. May 5, 2007 - 105 passengers and nine crew perished when they plummeted into a swamp on a Kenya Airways flight from Nairobi to Abidjan, Côte d'Ivoire. No one survived the crash. February 25, 2009 - A Boeing 737-800 used on a Turkish Airlines Flight skidded along a field after it tried to land at Amsterdam Schiphol Airport. Nine people died, including both pilots and a pilot-in-training, while 84 were injured. January 25, 2010 - An Ethiopian Airlines flight crashed into the Mediterranean shortly after taking off from Beirut en route to Addis Ababa, killing all 90 passengers. 22 May, 2010 - A 737-800 flight from Dubai, operated by Air India Express, crashed while trying to land in Mangalore, India, the third deadliest accident involving the series, killing more than 150 onboard. 16 August, 2010 - AIRES Flight 8250 departed from Bogota in the dark and crashed on the Colombian island of San Andres, seriously injuring nine. March 19, 2016 - A Flydubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62 onboard. April 17, 2018 - The left engine on a Southwest Airlines 737-700 failed and debris shot out, smashing a cabin window and causing explosive decompression. A woman was partially ejected from the aircraft and later died from her injuries. September 28, 2018 - A 737-800 flying from Pohnpei, Micronesia to Papua New Guinea crashed into a lagoon when it undershot a runway. One person died. Advertisement

The jet was new and had been checked two days ago, the Ukrainian airline said.

'The plane was in working order,' UIA company president Yevgeniy Dykhne told a briefing in Kyiv where he choked back tears.

'It was one of our best planes with a wonderful crew.'

It was the Kyiv-based carrier's first fatal accident, and it said it was doing everything possible to establish what had happened.

Just hours before the crash, the US Federal Aviation Administration had banned US airlines from flying over Iran, Iraq and the waters of the Persian Gulf due to the Middle East crisis.

Television footage showed debris and smouldering engine parts strewn across a field, and rescue workers with face masks retrieving bodies of the victims.

After dawn had broken, photos published by Iran's state-run IRNA news agency showed rescue officials in a farm field, with what appeared to be pieces of the aircraft laying nearby.

Rescue workers carried body bags and the passengers' personal items - including cases, clothes, a Santa Claus doll, English-language books and a boxing glove - were lying amidst the debris.

Search-and-rescue teams were combing through the smoking wreckage of the plane from Tehran to Kiev but officials said there was no hope of finding anyone alive.

'The fire is so heavy that we cannot (do) any rescue... we have 22 ambulances, four bus ambulances and a helicopter at the site,' Pirhossein Koulivand, head of Iran's emergency services, told Iranian state television.

The Ukrainian embassy in Iran initially issued a statement saying: 'According to preliminary data the plane crashed due to engine failure for technical reasons. As of now versions of terrorist attack or missile attack are ruled out.'

However, that claim had been deleted from the embassy website by Wednesday lunchtime, with an updated statement saying merely that the causes of the crash were under investigation.

Any previous comments about the cause were 'not official', the embassy said.

Iranian media quoted an aviation official as saying the pilot of the airliner did not declare an emergency.

Qassem Biniaz, a spokesman for Iran's Road and Transportation Ministry, said it appeared a fire struck one of the plane's engines.

The pilot of the aircraft then lost control of the plane, sending it crashing into the ground, Biniaz said, according to the state-run IRNA news agency.

A series of airlines have today announced they will stop flying over Iranian airspace. This map shows how routes might be affected

A British Airways flight from Mumbai to London was diverted to avoid Iraqi airspace, eventually stopping in Athens to refuel

This aerial view of the crash site shows bodies of the crash victims being laid out in bags after the plane came down today

Members of the International Red Crescent collect bodies of victims around the wreckage near Tehran today

Rescue workers search the scene where a Ukrainian plane crashed in Shahedshahr in the early hours of Wednesday

Emergency workers carry the body of one of the victims - with aviation experts divided over the likely cause of the crash

Rescuers carry a body bag at the crash site near Tehran today where 176 people were killed in the Ukrainian Airlines crash

People examine the wreckage of the Boeing 737 plane which came down only a few minutes outside Tehran this morning

Emergency services personnel walk amidst the wreckage after an Ukraine International Airlines Boeing 737-800 carrying 176 people crashed

Was the Ukrainian jet brought down by an Iranian missile - or were the 176 people on board killed by a mechanical failure? Here are the five key theories Theory one: Mechanical failure or pilot error Iranian authorities have said that initial investigations point to either an engine failure - or a catastrophic pilot error. The three-year-old Boeing 737 jet came down just three minutes after take-off from Imam Khomeini International Airport. Iranian officials said the pilot had lost control of the Boeing jet after a fire struck one of the plane's engines, but said the crew had not reported an emergency and did not say what caused the fire. Footage of the crash appears to show the plane streaking downwards with a small blaze on the wing, near its jet engines (pictured above on the ground). But critics have questioned the Iranian account, calling it the 'fastest investigation in aviation history' - and said the Boeing 737 has a largely outstanding safety record with no recent history of an engine failure of this kind. Ukrainian President Volodymyr Zelenskiy has instructed prosecutors to open criminal proceedings - a clear signal that he is unsure about Iran's version of events. His Government also revealed the plane was inspected just two days ago. Theory two: Accidentally hit by an Iranian missile The plane came down shortly after Iran launched its missile attacks Iraq with tens of ballistic weapons fired from the rogue state. Photographs of the downed Ukrainian airlines jet show that the fuselage appears to be peppered with shrapnel damage. Experts have said that an engine fire or pilot error does not explain those holes (pictured). Ilya Kusa, a Ukrainian international affairs expert, said amid the US-Iranian tensions and said: 'It is difficult not to connect the plane crash with the US-Iran confrontation. The situation is very difficult. One must understand that this happened shortly after Iran's missile attacks on US military facilities'. Just hours before the crash, the US Federal Aviation Administration had banned US airlines from flying over Iran, Iraq and the waters of the Persian Gulf due to the Middle East crisis. This was due to the possibility of missiles flying towards Iraq - and airlines are still skirting the region as they head to and from Asia. Theory three: Jet was deliberately brought down by a missile Video footage tweeted by the BBC's Iran correspondent, Ali Hashem, appeared to show the plane already burning in the sky before it crashed in a massive explosion. It sparked speculation that the jet could have been shot down accidentally by nervous Iranian air defence soldiers, hours after Iran fired 22 ballistic missiles at US bases in retaliation for the killing of general Qassem Soleimani. But there is a major question mark over whether Iran would shoot down a plane with so many of its own citizens on board. Many of the world's major airlines have stopped flying through or even near Iranian airspace as they cross the globe amid safety fears after US/Iran tensions boiled over in the past week. Iran is a key ally of Vladimir Putin's Russia, which grabbed Crimea from Ukraine and has been involved in an on-off conflict with its neighbour since 2014. Russia has denied shooting down the ill-fated MH17 jet five years ago - but experts say otherwise with three Russians arrested over the disaster. Theory four: An accidental drone strike Experts have speculated that the Ukrainian aircraft could have collided with a military drone before crashing. The drone may have smashed into the engine - or been sucked in - with the pilot unsighted because it was after dark. This could cause an explosion and the fire seen as the plane hit the ground (pictured). Experts said Iranian were in the air at the time - in case the US decided to fight back - and not always picked up by radar. Russian military pilot Vladimir Popov said: 'It could have been an unmanned reconnaissance aircraft, which are small in size and poorly visible on radars. A plane in a collision could get significant damage and even catch fire in the air.' Theory five: Sabotage or a terror attack Aviation experts have urged investigators to rule out whether the plane was brought down by terrorists or as an act of sabotage. They say that while a flaming engine is highly unusual, the sudden loss of data communications from the plane is even more so. This could be caused by a bomb, that blew up after the 737 took to the air, wrecking its systems. An electronic jammer weapon that knocked out the plane's controls could also explain it. British expert Julian Bray said it 'could be an altitude triggered device set to detonate during take off. Unusual that engine seen to be on fire before crash, points to catastrophic incident' or being 'deliberately brought down'. He added that based on the footage pilot error looks 'unlikely'. Experts had said that if the black box was not recovered by Iranian security officials (pictured) from the wreckage it could point to it being a deliberate act. It has been found, but Iran says it will not share the data with Boeing or Ukraine. After the crash the Ukrainian embassy in Tehran reported that the crash had been caused by an engine failure rather than terrorism - but this was later deleted on social media. Advertisement

An investigation team was at the site of the crash in southwestern outskirts of Tehran, Iran's civil aviation spokesman Reza Jafarzadeh said.

'After taking off from Imam Khomeini international airport it crashed between Parand and Shahriar,' Jafarzadeh said.

'An investigation team from the national aviation department was dispatched to the location after the news was announced.'

Iran's English-language broadcaster Press TV cited the Imam Khomeini International Airport spokesman as saying the crash was caused by 'technical difficulties'.

Critics have questioned the Iranian account, calling it the 'fastest investigation in aviation history' - and said the Boeing 737 has a largely outstanding safety record with no recent history of an engine failure of this kind.

Iran says it has found the plane's black boxes but will not give them to planemaker Boeing or the United States.

Ali Abedzadeh, the head of Tehran's civil aviation organisation, said it was not clear which country Iran would send the box to so that its data could be analysed.

Pictures at the scene appeared to show unexplained holes in the charred fuselage.

State media reported that the plane caught fire after crashing, but a video aired by the state broadcaster appeared to show the plane already on fire as it fell from the night sky.

Another theory is that the plane could have have collided with a military drone before crashing.

Ilya Kusa, a Ukrainian international affairs expert, said amid the US-Iranian tensions 'there were lots of them in the sky' immediately after the rocket attacks.

Russian military pilot Vladimir Popov said: 'It could have been an unmanned reconnaissance aircraft, which are small in size and poorly visible on radars.

'A plane in a collision could get significant damage and even catch fire in the air.'

Aviation experts were divided in their assessments of the crash today.

Stephen Wright, a professor of aircraft systems at Tampere University in Finland: 'There is a lot of speculation at the moment it has been shot down - I think that is not going to be the case at all.

'Planes fly the same routes day in, day out,' he said. 'You don't tend to put... missiles next to international airways for obvious reasons.'

He added: 'It could be a bomb or it could be some sort of catastrophic breakup of the aircraft.'

Against that, one aviation risk group said the first assumption should be that it was a 'shootdown event' like MH17 which was brought down by a suspected Russian missile over Ukraine in 2014.

A statement from OPS suggested there were 'obvious projectile holes in the fuselage and a wing section'.

'Whether that projectile was an engine part, or a missile fragment is still conjecture,' the group said.

'We would recommend the starting assumption to be that this was a shootdown event, similar to MH17 – until there is clear evidence to the contrary.'

Meanwhile, a former pilot and head of flight operations at Britain's Civil Aviation Authority cast doubt on the theory that a mechanical failure was to blame for the crash.

Captain Mike Vivian told Sky News that the Ukrainian Airlines crash was a 'puzzling accident'.

The Boeing aircraft was less than four years old and there was no sign of bad weather or pilot error, making it a 'difficult accident to explain', he said.

'It is a puzzling accident because the normal culprits like weather, like maintenance, like old aircraft or like possibly crew training - I don't believe they're present in this case,' he said.

'Obviously in this case they'll be trying to work out whether it broke up mid-air as indeed it appears to have done or whether it broke up when it hit the ground.

'They'll be looking for evidence of mechanical failure, although I find it difficult, troubling to suggest that engine failure may have caused this.

'Even with a double engine failure, these aircraft are capable of gliding - not far, but they can glide - so I find it very difficult to understand that.'

Today a series of airlines including British Airways and Air France have responded to the crash by routing their flights away from Iranian airspace, while German carrier Lufthansa said it was cancelling its daily route from Frankfurt to Tehran.

The region is a central corridor for flights between Europe and Asia, but aircraft can be rerouted fairly easily.

One British Airways flight from Mumbai to London was diverted to avoid Iraqi airspace, eventually stopping in Athens to refuel.

A BA spokeswoman declined to comment on exact routings, telling MailOnline: 'We are in constant contact with our partners around the world to assess the security of our routes, and will always take action where appropriate.

'We would never operate a flight unless it was safe to do so.'

Malaysia Airlines said that 'due to recent events,' its planes would avoid Iranian airspace, and Singapore Airlines also said that its flights to Europe would be rerouted to avoid Iran.

Ukraine International Airlines said it had indefinitely suspended flights to Tehran after the crash.

The rerouted flights were causing delays of up to an hour for passengers travelling over the Middle East.

The rescue group Red Crescent said teams were assisted by soldiers and firefighters in the effort to recover bodies.

'Obviously it is impossible that passengers' on flight PS-752 are alive, Red Crescent head Morteza Salimi told semi-official news agency ISNA.

Ukrainian president Volodymyr Zelensky voiced his condolences in a message from Oman.

'Terrible news from the Middle East,' he said. 'This morning, after taking off from the Imam Khomeini International Airport (Tehran), a passenger plane of Ukraine International Airlines crashed near the airport.

'According to preliminary data, all passengers and crew members were killed. Our embassy clarifies the information about the circumstances of the tragedy and the lists of casualties.

'My sincere condolences to the families and friends of all passengers and crew members.'

Zelensky ordered the creation of a crisis team to handle the accident including top ministers and managed by the country's national security agency.

His priority was the 'establishment of the truth and those responsible for this terrible catastrophe,' he said.

The agency said it has information about 167 passengers who had checked in for the flight as well as nine crew members, putting the total estimated number of people on the plane at 176.

Breaking down the numbers, officials said there were 82 Iranians, 63 Canadians and three Britons on flight PS752, along with 11 Ukrainians, 10 Swedes, four Afghans and four Germans.

Canada is home to a large Ukrainian and Iranian diaspora.

Prime minister Justin Trudeau said his government would work closely with investigators.

'I join Canadians across the country who are shocked and saddened to see reports that a plane crash outside of Tehran, Iran, has claimed the lives of 176 people, including 63 Canadians,' Trudeau said in a statement.

'I offer our deepest condolences to those who have lost family, friends, and loved ones in this tragedy.

'Our government will continue to work closely with its international partners to ensure that this crash is thoroughly investigated, and that Canadians' questions are answered.'

Andriy Shevchenko, Ukraine's ambassador to Canada, also expressed condolences.

'My heart is broken. We will have to go through this terrible pain together with our Canadian brothers and sisters,' he tweeted.

The crash marks one of the worst losses of life for Canadians in an aviation disaster.

In 1985 a bomb exploded and killed 329 people aboard an Air India flight, most of whom were Canadian.

Newlywed Tahmasebi, 35, from Chiswick, west London, was celebrating his marriage to bride Niloofar Ebrahim (pictured) in Iran when the pair perished in the Ukrainian Airlines tragedy

Businessman Mohammad Reza Kadkhoda-Zadeh (left) and engineer Sam Zokaei (right) both died in the crash

Two flight attendants in an experienced crew were Mariia Mykytiuk (left) and Valeriia Ovcharuk (right)

Pilot Vladimir Gaponenko (left) and flight attendant Denis Lykhno (right) were part of the crew on the doomed flight

Julia Solohub (left) and Igor Matkov (right) were also among the crew on board the doomed Ukrainian passenger flight

Canadian family killed in the Boeing plane crash in Iran pictured, left. The family were from Edmonton, capital of Canada's Alberta province, and have been named as father Pedram Mousavi, mother Mojgan Daneshman and daughters Darya Mousavi and Darina Mousavi. Pictured right is the Swedish family who were killed. Raheleh and Mikael Lindberg, 37 and 40, were killed along with their two young sons Erik, nine, and Emil, seven, after the Boeing 737 burst into flames following take-off from Tehran

Canadian victims of the Ukraine International Airlines crash in Iran, University of Alberta professors Mojgan Daneshmand and Pedram Mousavi, pictured in Edmonton, Alberta, Canada

The first of the three British victims was later named as father-of-one Mohammad Reza Kadkhoda-Zadeh, 40, who ran a dry cleaning business in East Sussex.

He is understood to have travelled to Iran to see family over the Christmas period and was returning to the UK via Ukraine.

The second victim, Saeed Tahmasebi Khademsadi, 35, was an engineer at construction firm Laing O'Rourke where he was today hailed as a 'popular and well-respected' colleague.

He had flown to Tehran with new wife Niloofar Ebrahim for the second leg of their wedding with friends and family after tying the knot at Wood Green register office in London last month.

The third, 42-year-old Sam Zokaei, was an engineer at BP where colleagues mourned a 'tragic loss' today.

The pilot was named as Vladimir Gaponenko who had 11,000 hours of experience.

Second pilot Serhiy Khomenko had 7,600 hours flying time - but unusually also on board was airline instructor Alexey Naumkin with 12,000 hours experience.

Flight attendant Maria Mikityuk, 24, was described as 'a very bright, beautiful, cheerful and sincere woman' hailing from Ivano-Frankivsk in Ukraine.

Her colleague Valeriia Ovcharuk was originally from Luhansk in rebel-held eastern Ukraine.

Another flight attendant, Denis Lykhno, was described 'a great guy and a good friend' who was remembered for 'learning everything in theist week' to pass exams.

Officials in Tehran said 15 children were among the passengers. The semi-official news agency ISNA said 13 were students from Tehran's Sharif University, the most prestigious in the country.

A UK Foreign Office spokesman said: 'We are deeply saddened by the loss of life in the plane crash in Iran overnight.

'We are urgently seeking confirmation about how many British nationals were on board and will do all we can to support any families affected.'

Debris of a plane belonging to Ukraine International Airlines which had been checked just days before it crashed

A rescue worker searches the scene where an Ukrainian plane crashed in Shahedshahr, south-west of the capital Tehran

Former pilot doubts mechanical failure theory A former pilot and head of flight operations at Britain's Civil Aviation Authority has cast doubt on the theory that a mechanical failure was to blame for the crash. Captain Mike Vivian told Sky News that the Ukrainian Airlines crash was a 'puzzling accident'. The Boeing aircraft was less than four years old and there was no sign of bad weather or pilot error, making it a 'difficult accident to explain', he said. 'It is a puzzling accident because the normal culprits like weather, like maintenance, like old aircraft or like possibly crew training - I don't believe they're present in this case,' he said. 'Obviously in this case they'll be trying to work out whether it broke up mid-air as indeed it appears to have done or whether it broke up when it hit the ground. 'They'll be looking for evidence of mechanical failure, although I find it difficult, troubling to suggest that engine failure may have caused this. 'Even with a double engine failure, these aircraft are capable of gliding - not far, but they can glide - so I find it very difficult to understand that. 'They'll also be looking obviously for evidence of foul play whether there was possibliy an internal device or whether there was a missile or something fired from the ground at the aircraft. 'The wreckage should reveal that, although clearly there are political sensitivities here bearing in mind the nature of the situation prevailing in Iran.' He added: 'Boeing are reeling at the moment, they've got numerous investigations on them and this would just be another hammer blow for them.' Asked about the safety of travelling over the Middle East, he said: 'If you're above about 30,000 feet, which most airliners travelling to and from India and the Far East are, there isn't a great risk at all. But to be prudent, airlines stay away. 'By and large, the risks are to the lower level. As far as I'm concerned, it's prudent to stay away from these areas. 'There's now a well rehearsed routine for avoiding and rerouting flights. It will take longer in some cases.' Advertisement

Zelensky's office said he had cut his visit to Oman short and was returning to Kyiv because of the crash.

The country's prime minister Oleksiy Honcharuk confirmed the casualty toll.

The Ukrainian nationals included two passengers and nine crew members. Airline officials said most of the passengers were transiting through Kyiv to other destinations.

'Our task is to establish the cause of the crash of the Boeing and provide all necessary help to the families of the victims,' said parliament speaker Dmytro Razumkov in a Facebook statement.

The airline said it was notifying passengers' families and working with aviation authorities 'to do everything possible to find the reasons for the aviation accident'.

'The plane was manufactured in 2016, it was received by the airline directly from the (Boeing) factory,' a Ukrainian International Airlines statement said.

'The plane underwent its last planned technical maintenance on January 6, 2020.'

An airline official said: 'Given the complexity of the flight there was a reinforced crew on this flight. Given the experience of the crew the chance of their making a mistake is minimal. We do not even consider such a chance.'

On a possible missile strike he said: 'There is nothing we have to confirm this yet. 'The information we gave you was a technical failure of the plane. It was one of our best crews.

'There was nothing by late last night suggesting to us that we needed to restrict flights.

'We have a right to make this decision and had there been a single threat we would have stopped the service.'

A number of 737-800 aircraft have been involved in deadly accidents over the years.

In March 2016, a Flydubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62 on board.

Another 737-800 flight from Dubai, operated by Air India Express, crashed in May 2010 while trying to land in Mangalore, India, killing more than 150 onboard.

Boeing, like other airline manufacturers, typically assists in crash investigations.

However, that effort in this case could be affected by the U.S. sanctions campaign in place on Iran since President Donald Trump unilaterally withdrew from Tehran's nuclear deal with world powers in May 2018.

Remains of the plane are seen as search and rescue works are conducted at the site near Tehran today

A handout picture provided by the Iranian Red Crescent shows rescue teams working at the crash site today

Search and rescue works are conducted at the crash site after the Boeing airliner came down in Iran this morning

There were no survivors among the 168 passengers and nine crew, Ukrainian president Volodymyr Zelensky said

Debris of the plane is seen at the crash site today with the cause of the crash yet to be fully established

Iranian President Hassan Rouhani had previously made veiled threats to American airliners after tweeting a reference to the 1988 Lockerbie bombing that killed 270 people.

Rouhani tweeted that America should 'never threaten Iran' after warning the US should 'remember the number 290' in reference to an incident when the US Navy accidentally shot down an Iranian passenger jet in the Persian Gulf in July 1988, killing 290.

Some Middle East experts have taken this as a veiled reference to the Lockerbie terrorist attack, which saw a bomb destroy Pan Am flight 103 over Scotland in December 1988 killing 270 - months after the downing of Iranian flight 655.

Libya has always been blamed for the Lockerbie bombing, and one of their intelligence agents was jailed in Scotland for the terror attack.

But Western spies believe Tehran played a role in the attack and executed it in revenge for the downing of the Iranian passenger jet.

The crash added to jitters in the Middle East just hours after Iran fired at least 15 missiles at US bases in Iraq in an operation called 'Martyr Soleimani'.

A US defence official told Military Times that Iran shot 15 missiles at Iraqi bases housing U.S. troops. Ten missiles hit al-Asad airbase, one missile hit Erbil International Airport in in the north, and four missiles failed in flight.

An Iraqi statement gave different figures, saying that 22 missiles were fired of which 17 hit the base.

Donald Trump tweeted that 'all is well' and 'so far so good' after the attack, with no early reports of casualties.

State television claimed that the missile strikes killed 80 Americans, but did not provide evidence and there was no such claim in US media.

Bodies of passengers are being carried from the site by search and rescue team members at the crash site

Rescue teams work amidst debris after a Ukrainian Airlines plane crashed just minutes into its journey

Rescue workers search the scene where an Ukrainian plane crashed in Shahedshahr this morning

Members of the Iranian Red Crescent group work at the crash site after the sun rose this morning following the crash

The head of Iran's emergency services initially said they may be able to save a few on board

Images show a helicopter and emergency vehicles at the scene of the crash as first responders worked to find any survivors

Ukrainian International Airlines flight PS752 carrying 176 people and heading to Kiev crashed near Tehran Wednesday

The UK's Ministry of Defence confirmed that no British military personnel were injured in the barrage, while Iraq and France also said they sustained no casualties.

Iran's foreign minister Mohammad Javad Zarif said Iran 'took and concluded proportionate measures in self-defence', but it is unclear whether the strikes will satisfy many Iranians' demands for retaliation against the US.

Supreme leader Ayatollah Ali Khamenei declared that 'military action like this is not sufficient' and demanded America's withdrawal from the region.

'Last night, a slap in the face was delivered,' Khamenei said in a speech broadcast live on state television.

Iran's Revolutionary Guards, which controls the country's missile program, confirmed that they fired the rockets just hours after the slain general's funeral, and reported the operation's name was 'Martyr Soleimani'.

Britain condemned the missile strikes, urging Iran 'not to repeat these reckless and dangerous attacks, and instead to pursue urgent de-escalation'.

'A war in the Middle East would only benefit Daesh and other terrorist groups,' said foreign secretary Dominic Raab, using an alternative term for ISIS.

German defence minister Annegret Kramp-Karrenbauer said the government in Berlin 'rejects this aggression in the sharpest possible terms.'

Debris is seen from a Ukrainian plane which crashed as authorities work at the scene in Shahedshahr

Authorities are seen carrying bodies away from the scene after the crash on Wednesday

Iranian Red Crescent's Relief and Rescue Organization said it was impossible for there to be any survivors

Later emergency responders said the fire was too heavy at the scene and they could do no rescue

Search and rescue works are conducted at site after a Boeing 737 plane belonging to a Ukrainian airline crashed near Imam Khomeini Airport in Iran just after takeoff with 180 passengers on board in Parand, Iran on January 08, 2020

The two-engine plane crashed between the cities of Parand and Shahriar. Debris is seen from a plane crash on the outskirts of Tehran, Iran

About 10 ambulances were on the scene after the crash as emergency responders tried to gather bodies

Search and rescue works were being conducted at site on Wednesday after a Boeing 737 plane crash

The airliner, said to be a Boeing 737, went down around Parand 60 kilometres south-west of the Iranian city Tehran. The aircraft took off 2.44am UTC (6:14am local time) on Wednesday and had reached 7,925ft

The Boeing 737, Ukrainian International Airlines flight PS752, went down near Tehran Imam Khomeini International Airport

According to the flight record, the plane was doing 275kts when it was downed. Flight data shows the three-year-old Boeing 737-800 reached an altitude of 2.4 km and then suddenly disappeared three minutes after take-off in Tehran

The burial for Revolutionary Guard Gen. Qassem Soleimani has taken place in his hometown earlier

Trump: 'So far, so good' as casualties and damage are assessed after Iran ballistic missile strike

President Donald Trump says 'all is well' and 'so far so good' as the damage and casualties continue to be assessed after Iran fired more than a dozen ballistic missiles at two Iraqi bases housing American troops in a revenge attack for the U.S. drone strike that killed a top Iranian general.

'All is well! Missiles launched from Iran at two military bases located in Iraq. Assessment of casualties & damages taking place now. So far, so good! We have the most powerful and well equipped military anywhere in the world, by far,' Trump tweeted late Tuesday as he broke his silence on the missile attack.

Trump said he would be making an official statement on Wednesday morning regarding the attacks.

The Ain al-Asad airbase in western Iraq that Trump visited in December 2018 and the Erbil base in Iraqi Kurdistan were both struck by the missiles on Tuesday at about 5.30pm (EST).

The Pentagon says the missiles were 'clearly launched from Iran' to target U.S. military and coalition forces in Iraq. A U.S. official said there were no immediate reports of American casualties, though buildings were still being searched.

A military official has revealed the U.S. had early warnings of the Iranian missile launches and were able to the sound the alarms at at least one of the two targeted bases. Those in harm's way were able to scramble to safety and hide in bunkers during the attack, the official told USA Today. U.S. troops at the base had been practicing safety drills for some time.

Iran's Revolutionary Guards, which controls the country's missile program, confirmed that they fired the rockets in retaliation for last week's killing of Iranian general Qassem Soleimani, according to state TV.

They reported the operation's name was 'Martyr Soleimani' and it took place just hours after the slain general's funeral.

Iran's foreign minister Javad Zarif called the attacks 'self-defense' but said they did 'not seek escalation' but would defend itself against further aggression.

Iran has fired more than a dozen ballistic missiles at two Iraqi bases housing American troops in a revenge attack for the U.S. drone strike that killed a top Iranian general

The Ain al-Asad airbase in western Iraq that was visited by Donald Trump in December 2018 and the Erbil base in Iraqi Kurdistan were both struck by the missiles on Tuesday at about 5.30pm (EST)

The Pentagon says the missiles were 'clearly launched from Iran' to target U.S. military and coalition forces in Iraq

The rockets used in the attack, according to Iranian TV, were Fatteh-110 ballistic missiles, which have a range of 186 miles or 300km.

The Iranian air force has since deployed multiple fighter jets to patrol it airspace, according to reports - as Iran warned the U.S. and its allies in the region not to retaliate.

Iranian missiles that blitzed Iraqi airbases can deliver a precision-guided 500lb warhead over a range of more than 180 miles Two types of ballistic missiles were reportedly used to hit U.S. Military bases in Ain al-Asad in western Iraq and also around Erbil in Iraqi Kurdistan. The majority of those used are believed to be the Fateh-110, which can travel 180 miles or 300km and have a payload of around 500lb. Reports also suggest the Qiam-1 was also used, a short range ballistic missile produced by Iran which can travel 500 miles and carry 750lb warheads. The Fateh-110 is an Iranian-designed, short-range, surface-to-surface ballistic missile that can be launched from any location. While the Qiam-1 was specifically built to target U.S. bases in the Middle East, which have 'encircled Iran', according to Iranian sources. When it was launched the Fateh-110 was described by Iranian defence minister Brigadier General Amir Hatami as '100-percent domestically made - agile, stealth, tactical (and) precision-guided'. Both missiles are reported to have been fired from Tabriz and Kermanshah provinces in Iran. Advertisement

The Pentagon said it was still working to assess the damage.

'In recent days and in response to Iranian threats and actions, the Department of Defense has taken all appropriate measures to safeguard our personnel and partners. These bases have been on high alert due to indications that the Iranian regime planned to attack our forces,' a statement from the Pentagon read.

'It is clear that these missiles were launched from Iran and targeted at least two Iraqi military bases hosting U.S. military and coalition personnel at al-Assad and Irbil. We are working on initial battle damage assessments.

'As we evaluate the situation and our response, we will take all necessary measures to protect and defend U.S. personnel, partners, and allies in the region.'

The Islamic Revolutionary Guard Corps, a branch of the Iranian Armed Forces, reportedly said Iran's supreme leader Ayatollah Khamenei was personally in the control center coordinating the attacks.

They also warned U.S. allies in the Middle East that they would face retaliation if America strikes back against any Iranian targets from their bases.

'We are warning all American allies, who gave their bases to its terrorist army, that any territory that is the starting point of aggressive acts against Iran will be targeted,' they said. It also threatened Israel.

Defense Secretary Mark Esper and Secretary of State Mike Pompeo were spotted arriving at the White House soon after news of the strikes broke.

South Carolina Senator Lindsey Graham said on Tuesday night that the missile strikes were an 'act of war' and said Trump had all the power he needed to act.

'This is an act of war by any reasonable definition,' Graham told Fox News' Sean Hannity. 'The President has all the authority he needs under Article II to respond.'

House Speaker Nancy Pelosi tweeted that the U.S., as well as the rest of the world, 'cannot afford war'.

'Closely monitoring the situation following bombings targeting U.S. troops in Iraq. We must ensure the safety of our servicemembers, including ending needless provocations from the Administration and demanding that Iran cease its violence. America & world cannot afford war,' she tweeted.