What we know so far about Boeing plane that crashed in Iran

On Wednesday morning, a Ukraine International Airlines flight carrying 167 passengers and nine crew en route to Kyiv crashed minutes after takeoff from Tehran's main airport. Here's what we know so far about the aircraft.

What do we know about the flight?

The flight number was PS752. 

It was scheduled to take off from Imam Khomeini International Airport at 5:15 a.m. local time, but was delayed about an hour.

It took off from Tehran at 6:12 a.m., heading west, but never made it above 2,400 metres in the air, according to data from the flight-tracking website FlightRadar24.

It had been expected to arrive in Kyiv about 4 hours and 15 minutes after takeoff.

According to Ukrainian Airlines, 168 people purchased tickets for the flight. That suggests one person did not board the flight.

All passengers were killed, including 63 Canadians.

What model was the plane?

It was an American-made Boeing 737-800, a twin-jet aircraft with CFM-56 engines. 

The original 737 launched in 1965. 

As of March 2018, more than 10,000 Boeing 737s had been assembled in Renton, Wash., breaking the Guinness World Record for "highest production large commercial jet," Boeing says. 

The 737-800 — one of the planes billed as "next-generation" 737s —  launched in Sept. 5, 1994. 

It carries 162 to 189 passengers.

What Canadian airlines fly this plane?

Canadian airlines that fly the 737-800 include:

• Air Transat.
• Flair Airlines.​
• ​​​​​​Sunwing.
• WestJet.

What do we know about the engine?

The CFM-56 engine is made by CFM International, a partnership between General Electric and Safran Aircraft engines. CFM says it is the main worldwide engine supplier for commercial aviation, with more than 33,000 CFM-56s delivered since 1974.

Two versions of the engines power the Boeing 737 next-generation family and the Airbus 320 family of planes, respectively.

In Paris on Wednesday, a spokesperson for the company said speculation regarding the cause of the crash was premature. 

How safe is the Boeing 737-800?

According to aviation expert John Cox, chief executive officer of Washington, D.C.-based Safety Operating Systems, the plane is a "workhorse airplane" that has been in service for many years with a "very, very good safety record." That's unlike the Boeing 737 Max, a newer plane that has been grounded after two fatal crashes in Indonesia and Ethiopia that killed 346 people within five months in 2018 and 2019.

Cox called the crash in Tehran "very unusual" for 737-800.

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In a statement on Wednesday, Boeing said: "We are in contact with our airline customers and stand by them in this difficult time. We are ready to assist in any way needed." It declined further comment. The company's shares fell 1.1 per cent on Wednesday.

Are there any known problems with this Boeing model?

As of November, about 50 737-800 planes around the world had been grounded after being found with cracks between the wings and fuselage. The U.S. Federal Aviation Administration had ordered inspections for the defect on all Boeing 737 next generation aircraft with more than 30,000 takeoff and landing cycles.

Has the plane been involved in any crashes?

Yes, this is the seventh fatal crash of a Boeing 737-800 since 2006. There have also been 10 incidents since in which passengers were injured but not killed.

How safe is the airline?

Ukraine International Airlines says this is its first crash since it was founded in 1992.

The plane involved in the crash was purchased in 2016 and inspected on Monday of this week.

What about this crash?

According to the plane's radar data, the plane took off and climbed normally during the first two minutes of the flight. Then it stopped transmitting data.

Cox says that indicates something probably interrupted the power to the transmitters. Typically, he says, when that happens, a second generator will supply power. That does not appear to have happened in this case. He called it "very unusual."

Larry Vance, a former pilot and Transportation Safety Board accident investigator, told CBC News Network that losing the signal like that indicates that something "catastrophic" had to have happened. He noted that the plane has "lots of sources and lots of backups" for power.

Do we know anything about the cause?

Iranian officials said they suspect a mechanical issue brought down the 3½-year-old Boeing 737-800 aircraft. Ukrainian officials initially agreed, but later backed away and declined to offer a cause while the investigation is ongoing.

Keith Mackey, president of Mackey International, an aviation consulting firm specializing in safety and risk management, suggested that, given the plane's recorded speed and altitude during takeoff, which were normal, and the fact that it landed very close to its last recorded location, the cause was probably not an engine failure.

Mackey, a former pilot and aircraft accident investigator, said an engine problem would have made the plane unable to climb that quickly. He added that in the case of an engine fire or similar problem, the pilots would likely have been able to steer the plane and land it safely.

"We know the the aircraft very suddenly and inexplicably descended," he told CBC News Network Wednesday morning.

"What happened is consistent with what we would expect to happen if there was a bomb blast or some sort of explosion on the aircraft."

Vance said the type of catastrophic event that downed the plane could include a missile, a bomb or a catastrophic engine failure in which pieces of the engine broke apart and flew into the plane.

Gen. Abolfazl Shekarchi, a spokesperson for the Iranian armed forces, was quoted by the semiofficial Fars news agency as denying the plane has been brought down by a missile, The Associated Press reported.

Meanwhile, Ukraine International Airlines president Yevhen Dykhne said the aircraft "was one of the best planes we had, with an amazing, reliable crew."

In a statement, the airline went further, saying: "Given the crew's experience, error probability is minimal. We do not even consider such a chance."

Five security sources — three Americans, one European and one Canadian — who asked not to be named, told Reuters the initial assessment of Western intelligence agencies was that the plane had suffered a technical malfunction and had not been brought down by a missile. There was evidence one of the jet's engines had overheated, the Canadian source said.

How is the investigation proceeding?

The two black boxes and the flight data recorder have been recovered, report officials in Iran. However, they say the data will not be handed over to U.S.-based Boeing. 

Under international rules, responsibility for investigating the crash lies with Iran. 

Tensions are high between Iran and the U.S. following a drone strike ordered by U.S. President Donald Trump that killed Iranian Gen. Qassem Soleimani in Baghdad on Friday. Iran fired missiles at U.S. military bases in Iraq Wednesday morning local time in response to the killing, just hours before the plane crash.

Cox said if the Iranian government is uncomfortable sending the flight data to Boeing, then it should be sent to a third-party investigative agency to read and publish.

"We need answers to make sure that something like this doesn't occur, and the families of these victims deserve the answers," he said. "The politics between two governments has no place — no place at all in an accident investigation."

Canadian Transport Minister Marc Garneau tweeted Wednesday that the government has reached out to Iranian officials to offer technical assistance.

In the meantime, Cox said investigators need to get on-site and download and analyze the data, which will take some time: "The hardest part right now is patience."