Radio silence and a desperate turn: The final moments of Flight PS752

Ukraine International Airlines Flight PS752 lifted off from Tehran's Imam Khomeini airport at 6:12 a.m. local time Wednesday — almost an hour late.

The regularly scheduled trip to Kyiv was supposed to take just under four hours. But something went disastrously wrong for the Boeing 737-800 within minutes.

Tracking data suggests the flight climbed to just over 2,400 metres and reached a speed of 500 km/h before it plunged back to earth, crashing near a soccer field and irrigation canal outside the town of Parand, about 30 kilometres northwest of the airport.

Video broadcast by Iranian state TV shows what purports to be the final moments of the flight, with flames coming from an aircraft, then a blinding flash lighting up the pre-dawn darkness as the plane carrying nine crew and 167 passengers — 63 Canadians among them —  slams into the ground.

By the time the sun rose, an hour later, the search for survivors had already been abandoned. 

The plane, fully loaded with fuel for a 2,300-kilometre flight, exploded on impact. Footage from the scene shows smoldering piles of debris scattered across a wide area. 

63 Canadians among the dead after a plane crashes after takeoff in Iran 0:29

A full list of the names of passengers and their birth years — ranging from 1950 to 2016 — was made available by authorities in Tehran and Kyiv within hours of the tragedy. And Ukrainian Foreign Minister Vadym Prystaiko sent out a tweet in what was the middle of the night in North America confirming their nationalities: 82 Iranians, the 63 Canadians, 11 Ukrainians including the crew, 10 Swedes, four Afghan nationals, and three citizens each from the U.K. and Germany.

The timing of the tragedy — just four hours after the Iranians launched a barrage of missiles at two bases housing U.S. and other international military personnel in Iraq, an initial reprisal for the Americans' Jan. 3 killing of Gen. Qassem Soleimani — raised fears that the plane might have been shot down, or sabotaged. 

Shortly after the attacks on Tuesday evening (eastern time), the U.S. Federal Aviation Authority issued restrictions prohibiting American commercial carriers from flying over Iran, Iraq and the waters of the Persian Gulf. 

But Iranian officials were quick to attribute the crash to a mechanical failure. On Wednesday, Qassem Biniaz, a spokesperson for Iran's Transportation Ministry, told state-run media that it appeared the pilot had lost control after a fire started in one of the plane's engines.

Whatever occurred, it happened quickly: Hassan Rezaeifar, the chief crash investigator for Iran's Civil Aviation Organization, said the pilot never declared an emergency, and wasn't in communication with air traffic control during the final moments of the flight.

Rescue workers had already recovered both of the Boeing 737's black boxes, Iranian media reported.

Ukrainian officials aren't jumping to any conclusions.

President Volodymyr Zelensky has instructed the country's prosecutor general to set up a commission to investigate the crash, and is also ordering immediate inspections for all passenger planes.

"All possible versions of what occurred must be examined," Zelensky wrote in a Facebook post. 

At a morning news conference at the Boryspil International Airport in Kyiv — Flight PS752's destination — executives from Ukraine International Airlines described the plane's crew as "excellent," "reliable," and highly trained. They said the aircraft underwent routine maintenance on Monday, and there were no reports of problems prior to takeoff. 

Flight logs show the plane, which was delivered to the airline by Boeing in mid-2016, had already made 22 trips since Jan. 1, travelling to and from Tehran, Paris, Milan and London. 

The airline announced an indefinite suspension of its five-day-a-week service to Tehran, pending the outcome of the investigation.

The crash is the first fatal accident for the airline, which was founded in the 1990s and operates a fleet of more than 40 Boeing and Embraer jets.

The 737-800 is an older generation of Boeing, with a different flight control system than the troubled 737 Max, which has been grounded worldwide as a result of crashes in Indonesia and Ethiopia in October 2018 and March 2019. Although, there have been a number of fatal crashes involving 737-800s, including a March 2016 disaster in Rostov-on-Don, Russia, that killed 62 people, and a May 2010 crash in Mangalore, India, that killed more than 150 people.

On Wednesday evening, Tehran time, Iran's Civil Aviation Organization released its initial report on Flight PS752. The document, written in Farsi, says communication with the aircraft was lost at 6:18 a.m., shortly after the pilot had been cleared to ascend to 8,000 metres. Witnesses on the ground — and other flight crews in the air — reported seeing flames coming from the plane.

The report says an emergency signal was activated, but the transmitter antenna became disconnected at some point as the plane was going down. And it also says the aircraft was on a path to return to Imam Khomeini International when it hit the ground.

Iranian authorities say they have reached out to their counterparts in Ukraine, the U.S., Sweden and Canada for help in the investigation and assistance in identifying and repatriating the dead.

The Transportation Safety Board of Canada says it has appointed an expert to receive and review information from the Iranian investigators. 

A team of crash experts from Ukraine is already en route to Tehran, the report from Iran's Civil Aviation Organization says.