There are suspicions in the west, denials in Tehran, grim echoes for Ukraine, and grief spread far and wide
It was still dark when Ukraine International Airlines flight 752 took off on Wednesday from Tehrans Imam Khomeini airport. Onboard were 176 people. Most were returning home after holidays spent with families and friends in Iran. They were couples, newlyweds, students.
A mother and a daughter Sahar Hagjjoo and her eight-year-old child Elsa posed for a photograph together after taking their seats. A sweet one, with the pair relaxed, smiling, a little tired from the early start. Everyone on the plane would have known of the strained diplomatic circumstances swirling before them.
Three days earlier the Trump administration had assassinated the Iranian general Qassem Suleimani in a devastating drone strike, soon after he landed in Baghdad. His killing provoked national mourning in Iran, defiance from the regime and threats of fiery revenge.
Retaliation arrived in the shape of Iranian missiles launched against US military bases in Iraq. Rockets crashed into a joint US-Iraqi facility in Erbil, in Kurdish northern Iraq, and at a US airbase in Anbar province. By design or accident, no one was hurt.
In the immediate aftermath of these strikes Irans armed garrisons must have been in a state of jittery high alert, wondering what the volatile Donald Trump might do next. Another US attack against domestic Iranian targets? A pause? Something else?
It was against this war-like backdrop that the plane took off at 6.12am. It climbed rapidly, reaching almost 8,000ft (2,400 metres). Its destination was Ukraines capital, Kyiv. From there most passengers were heading off elsewhere. More than a third were Iranian Canadians, going to Toronto or Edmonton.
Four British nationals were connecting to London. They included Mohammad Reza Kadkhoda-Zadeh, who ran a dry cleaning business in Hassocks, West Sussex; Sam Zokaei, a BP employee and Saeed Tahmabessi, an engineer.
The plane would have appeared on the radar screen of Irans Mehrabad air traffic control centre, which cleared the crew to ascend to 26,000ft. Staff should have identified the Boeing 737-800 plane as a regular civilian jet.
Also tracking the skies over Tehran were American satellites. If further missiles were hurled at US targets in Iraq the USs Space-Based Infrared System would immediately detect them.
At 6.15am the system picked up something ominous: the unmistakable heat signature of missiles freshly launched.
An Iranian garrison on the ground, due west of the airport, appears to have mistaken the plane for a hostile American object. According to US officials, an Iranian anti-aircraft battery unleashed two Russian-made missiles. The US satellites recorded an infrared blip: an explosion.
The results were immediate and catastrophic.
Mobile phone footage captures the moment of impact: a white flash, flaring across the inky heavens. Twenty four seconds later the sound arrives a boom and martial roar. Down on earth a dog barks. Further footage shot from a different standpoint shows the stricken plane hitting the ground, a burst of orange.
The missiles would have exploded adjacent to the plane, sending a deadly hail of shrapnel into the fuselage. The pilots made a doomed attempt to turn back, judging from the position of wreckage strewn across Tehrans outskirts. Take-off to crash landing was five minutes. The journeys last moments must have been ones of terror.
As dawn broke, rescuers found an awful scene. Bodies, personal belongings, parts of the wing, oxygen masks were scattered over farmland. The dead were put into plastic sacks. As Washington, Ottawa, Kyiv and London demanded answers, and relatives began to grieve, the Iranian authorities said the incident was a tragic case of mechanical mishap.
There were early hints, however, that this version of events might not be quite true. Ukrainian investigators and western journalists reported seeing men in uniform remove fragments of the plane. A bulldozer began to clear the site. Iran said it would not hand over the black box to foreign experts. This was damaged but intact.
Meanwhile, photographs circulated on social media showing what looked like a missile head with cone and fins lying in a nearby drainage ditch. A compelling clue or fake news? Initially, Ukraines president, Volodymyr Zelenskiy, said the plane had crashed as a result of an accident. Within hours, his government deleted this statement.
Behind the scenes, western governments were carefully picking over the satellite record. It confirmed that the Revolutionary Guards Parandak garrison had used a short-range Tor-M1 missile system to bring down the plane. Seemingly, its nervous operators had confused it with a US military jet. Or a reconnaissance drone.
In 2005 Tehran bought 29 Tor-M1s from Moscow. They consist of a missile launcher and radar in a single tracked vehicle. The weapon system is highly effective against short-range targets, with a range of 7.5 miles (12km), up to an altitude of 20,000ft.
For Ukraine, these details were a grim echo of six years ago. In summer 2014, as part of a covert invasion, the Russian military smuggled a Buk missile launcher into rebel-held eastern Ukraine. Its Russian crew accidentally shot down an overflying civilian plane, Malaysian airlines flight MH17, killing all 298 people onboard.
Dutch and international investigators subsequently confirmed Russias role. Moscow rejected this. Ever since it has offered implausible counter-versions.