In this photo released by the official website of the office of the Iranian Presidency, President Hassan Rouhani, left, meets family of Iranian Revolutionary Guard Gen. Qassem Soleimani, who was killed in the U.S. airstrike in Iraq, at his home in Tehran, Iran, Saturday, Jan. 4, 2020. Two days before a Ukraine International Airlines plane crashed near Tehran, killing everyone on board, Iranian President Hassan Rouhani invoked the memory of another doomed flight taken out of the sky by a missile. (Iranian Presidency Office via AP)

OTTAWA - Two days before a Ukraine International Airlines plane crashed near Tehran, killing everyone on board, Iranian President Hassan Rouhani invoked the memory of another doomed flight taken out of the sky by a missile.

Part of Rouhani's Jan. 6 tweet read "remember the number 290" — a reference to all those aboard Iran Air flight 655, mistakenly shot down in 1988 by an American missile.

Rouhani ended his message aimed at U.S. President Donald Trump with an ominous warning: "Never threaten the Iranian nation."

The Iran Air incident three decades ago and the 2014 downing of Malaysian Airlines flight MH17 provide lessons for investigators now probing — or confirming — Wednesday's deadly crash.

"It's so deja vu," said Michael Bociurkiw, who was an observer for the MH17 investigation with the Organization for Security and Co-operation in Europe. "They're becoming more similar by the day."

Investigators working the case, guided by international rules, would look into various possibilities despite news Thursday that western intelligence agencies, including in Canada, believe an Iranian surface-to-air missile downed Flight PS752 minutes after takeoff from Tehran's airport.

Iran disputes that theory.

The international team of investigators, headed by Iran's civil aviation authority, would go over every piece of evidence that they find at the crash site to see if there is shrapnel, for instance, from a missile in any piece of the plane or the bodies of the victims.

Bociurkiw said that was something MH17 investigators did, because the missile in that instance was designed to explode outside the target and send shrapnel into the fuselage — the main body of the aircraft — making the plane no longer airworthy.

Even the smallest piece of evidence, he said, may hold clues to verify the cause of the crash.

The site where the Ukrainian jetliner went down has apparently been contaminated, with officials unable to cordon off the area and people walking away with pieces before they can be catalogued.

"The fact that wreckage has moved before the team of investigators that should be there have the opportunity to look at it and examine it and do it all properly, that's entirely outside the norm," said Larry Vance, a former investigator with the Transportation Safety Board.

"It's extremely detrimental to the investigation, to the credibility of the investigation."

Further straining credibility are concerns about Iran's unwillingness to share the plane's flight data recorders, known as the "black boxes," particularly with American officials.

Some of that unease stems from the Iran Air incident.

On July 3, 1988, near the end of the Iran-Iraq war, an American navy ship known as the Vincennes accidentally fired two missiles at Flight IR655 as it took off from Bandar Abbas International Airport in south Iran. All 290 people on board died because officers mistook the Airbus A300 for a fighter jet.

The tragedy created a lingering distrust of the United States in Iran.

The black boxes might not be as central to this latest incident, however, because the Ukrainian airplane would have been sending information to the ground before losing contact.

The area would also have been watched by military radar or overhead satellites while infrared images and footage could also be used, said Richard Aboulafia, an aviation analyst with Teal Group in the Washington, D.C., area.

Pointing to the Vincennes incident, Aboulafia said there wasn't much to learn other than there had been a horrible error.

"I suspect that will be the outcome of this horror," he said.

Much like with MH17, some of the probe could come down to investigating the people involved in firing the missile.

"What's the objective here? It's to make the system safer," Aboulafia said.

"That means, in this case of MH17 and in the case of Vincennes, it's less about the airplane and more about ... the chain of mistakes that happened and what can be avoided."

In MH17, the lesson was to avoid airspace over a conflict zone, he said.

Elaine Parker, vice-president of the Canadian Society of Air Safety Investigators, said while the black boxes and scene are important for investigators trying to rule out possible causes of the crash, the majority of evidence comes from elsewhere, such as maintenance records for the airplane, satellite and air traffic control information.

If the evidence points to a missile strike, then the air-safety investigation comes to a stop.

Air-safety investigators follow guidelines set out by the International Civil Aviation Organization (ICAO) known as Annex 13.

But if investigators conclusively say a missile took down the Ukrainian plane, then another document takes over.

Annex 17, as it's known, is a restricted document that lays out how security experts should probe "an act of unlawful interference," Parker said.

That can mean anything from an unruly passenger, a hijacking, hostage-taking, tampering with a smoke detector — or a missile strike.

And with Annex 17 comes a cone of silence around the investigation because of the sensitive information involved.

"You are about to hit a wall that is really impenetrable," Parker said.

"I've been involved enough in security (investigations) to say you don't get to know everything because that's part of how we protect ourselves."

This report by The Canadian Press was first published Jan. 10, 2020.

News from © The Canadian Press, 2020