Verifying whether the Ukrainian passenger plane that crashed in flames near Tehran on Wednesday was hit with a missile should be far more straightforward than the heated rhetoric surrounding the event.
Surface-to-air missiles leave a distinctive trail of evidence after striking an aircraft, such as the pattern of pockmarks in the fuselage, shrapnel wounds in people who were on board – and in the data left behind on flight recorders.
“It looks like a shotgun pattern wherever they hit,” said Robert Swaim, a retired US crash investigator who has been involved in such cases. “There is a concentrated area of sharp little tears.”
The prime ministers of Canada, the UK and Australia all said on Thursday that they had intelligence showing that the Boeing 737-800 that crashed on Wednesday near Tehran was probably brought down by an Iranian missile and called for an international investigation of the disaster.
They did not specify the nature of the intelligence, but a person familiar with the inquiry said a US spy satellite detected two missiles being launched from an Iranian battery near where Ukraine International Airlines Flight 752 was passing overhead.
“We have intelligence from multiple sources, including our allies and our own intelligence. The evidence indicates that the plane was shot down by an Iranian surface-to-air missile,” Canadian Prime Minister Justin Trudeau told reporters in Ottawa.
Iran’s chief civilian aviation regulator, Ali Abedzadeh, on Thursday issued a strong denial that a missile had been involved, saying “it’s not possible”.
But the tell-tale signs should be obvious to experts who have examined previous such instances, such as the Dutch team that issued findings after Malaysian Airlines Flight 17 was shot down over eastern Ukraine in 2014, Mr Swaim said.
The photos of the wreckage near Tehran available so far on the internet do not necessarily indicate a missile, he added. Investigators cataloguing the twisted pieces of metal at the scene should be able to tell within a day or two if there are signs of puncture marks.
A photograph showing what appeared to be the charred head of an SA-15 missile could be an intriguing clue, he said. But investigators would need to verify it was related to the crash.
In some previous instances, the cause was obvious within hours. In others, it took months or years to document what happened.
In 2003 a DHL cargo jet was struck by a surface-fired missile shortly after taking off from Baghdad during the US-led occupation of Iraq, forcing pilots to make an emergency landing. No one was hurt.
In 1988, a US Navy missile cruiser, the USS Vincennes, downed an Iran Air Airbus A300 over the Arabian Gulf, killing 290 passengers and crew. The US military said it mistook the airliner for an Iranian fighter jet, an account disputed by Iran.
A Ukrainian air-defence station accidentally shot down a Siberian Airlines jet over the Black Sea in 2001, killing the 78 passengers and crew on board. Russian investigators concluded that the Ukrainian forces had fired two missiles at a drone as part of a military exercise, and one of them flew about 240 kilometres past its target and detonated near the airliner, causing it to plunge into the sea, the New York Times reported at the time.
The July 2014 episode involving the Malaysian Airlines plane has been one of the most well documented cases. The Boeing 777 carrying 298 people was shot down by a Russian-made Buk surface-to-air missile fired from rebel-controlled territory in eastern Ukraine. The region is the site of a conflict between pro-Russia separatists and Ukrainian military forces and two military aircraft had been downed just days earlier, an international team concluded.
Three Russians and a Ukrainian were charged with murder over the attack and a trial in the Netherlands is scheduled for March.
The final report by Dutch investigators was able to rule out actions by the pilots and other possible sources, such as a lightning strike.
The evidence of a missile was overwhelming, the investigation concluded.
An analysis of sound waves captured by the jet’s crash-proof cockpit recorder revealed that a powerful sound wave consistent with an explosion occurred milliseconds before the recording stopped as the plane broke apart.
Measuring the minute differences in when the sound wave hit different microphones in the cockpit, investigators concluded it was centred just to the left of the nose of the aircraft.
That corresponded to an analysis of puncture marks around the left side of the cockpit, investigators concluded.
Investigators found distinctively shaped pieces of shrapnel in three crew members’ bodies and tied them to the Buk missile system used in the attack, the report said.
In the latest case in Iran, the outlines of what happened should emerge soon, particularly if there is the shotgun pattern of shrapnel, Mr Swaim said.
“If there is some physical evidence in the wreckage like this, you’ll see it pretty quick,” he said. “Within the first day or two.”