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Release of Iran’s final safety investigation report into the downing of PS752

Associated links (A20F0002)

Kathy Fox, TSB Chair
Natacha Van Themsche, Director of Investigations (Air)
18 March 2021

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On January 8, 2020, Ukraine International Airlines flight 752 was shot down shortly after taking off from Tehran’s international airport, killing all 176 people on board, including 55 Canadians, 30 permanent residents and dozens of others with ties to Canada. Within a few short hours following this tragedy, the TSB advised Iran’s Aircraft Accident Investigation Board (or AAIB) that we would appoint an Expert in accordance with Annex 13 to the Convention on International Civil Aviation and we accepted Iran’s invitation to visit the accident site. From that day forward, we have been fully engaged in doing as much as possible to find out what happened, why it happened and what needs to change to prevent such a tragedy from happening again.

As a matter of practice, the TSB does not comment on reports from other agencies. However, given this unprecedented situation, where the state whose military was implicated in the event led the investigation, and given its impact within Canada, we feel that it is important to publicly convey our independent assessment of the final report. 

But before I discuss the contents of Iran’s final investigation report, I will speak briefly about the investigation process itself.

First, I’d like to remind everyone that a safety investigation is not intended to attribute blame or determine civil or criminal liability. Other processes are better suited for that. Experience has shown that an independent and thorough safety-focused investigation usually offers the best chance of finding out what really happened and why, providing the answers that everyone is asking for, particularly the families who lost so much.

ICAO Annex 13 prescribes the roles of participating countries, including which state has the right to lead the investigation, and which other states may participate and to what extent. It should be noted that, in the case of PS752, the Transportation Safety Board of Canada had no jurisdiction to lead or conduct a parallel investigation.

From the very beginning, Iran offered the TSB more access to the investigation activities than we were technically entitled to, but less than what we asked for. For example, two TSB investigators spent six days in Tehran following the crash, visiting the accident site, examining the wreckage, and meeting with Iranian safety investigators to review information gathered by their team. Later, they also met with Iranian, Ukrainian, and French investigators in Kiev before returning to Canada.

In July of last year, our Expert and a TSB recorder specialist attended the readout of the aircraft’s flight recorders in Paris. Throughout the course of the investigation, we were in direct contact with Iran’s AAIB and attended many discussions with the other participating countries. However, in spite of multiple requests, we were never formally accorded the higher status of accredited representative and hence were not allowed to listen to the cockpit voice recorders or directly access the flight data recordings.

At Ukraine’s request, in early February of this year, we were invited to provide them technical assistance, and Ukraine gave us access to the draft safety report for review and comments, something we would not otherwise have been entitled to.

Throughout this process, we have specifically asked Iran’s AAIB to answer 3 important questions –

In addition, we submitted dozens more detailed questions related to these 3 main lines of inquiry, that we believed the final investigation report needed to address in order for it to be seen as thorough and credible.

Since receiving Iran’s draft investigation report, our team has carefully reviewed and analyzed its contents and has now compared it to the final report.  Today we want to share our perspective discussing how the report answers the 3 main questions.

Sequence/factors leading to the shootdown by the Islamic Revolutionary Guard Corps (IRGC)

Iran’s final report concludes that PS752 was shot down because an air defense unit mistook the B737 aircraft as a threat. This misidentification reportedly occurred because of a misalignment of the missile launcher’s radar. Furthermore, the operator did not receive permission to shoot from senior officers, as he should have. To date, Iran has provided no evidence to support this scenario; however, it is a plausible explanation for what happened. The report does not provide detailed information regarding how the misalignment occurred, nor what steps were taken to ensure it was properly calibrated, the missile operator’s training, experience, or proficiency, nor about how or why the required communications with central command were either not followed or were unsuccessful. The report frames this action in the context of the heightened military alert given their expectation of retaliation following Iran’s earlier launch of missiles against Iraqi air bases housing U.S. military personnel but does not discuss what supervision or oversight was provided of field operations by Iran’s command and control system. The AAIB says that military activities fall outside of the scope of an Annex 13 investigation– we do not agree.

Nor does the report discuss what steps the Islamic Revolutionary Guard Corps has taken since then to identify the underlying safety deficiencies that allowed such an error to occur, nor what safety action has been taken to prevent such a mistake from happening again. Without this, how can the international civil aviation community be reassured that such a tragic error won’t happen again?

Why did the airspace remain open?

Iran’s final report generally explains the risk assessment process and mitigations that its civilian authorities took in coordination with the military, given the uncertainty of a retaliatory strike following their launch of missiles into Iraq. For example, the report says that Iran gradually cleared air traffic from using certain air routes to the west, from which direction they thought a retaliatory strike might come, and required military approval for each aircraft’s departure from civil airports such as Tehran’s International airport. However, Iran did not completely close its airspace to civilian aircraft.

Why did commercial airlines continue to operate?

In spite of being in a state of heightened military alert, Iran did not publish any notices to warn aircraft operators of these hazards, as recommended by ICAO, until after PS752 was shot down. The U.S. Federal Aviation Administration did post a warning; however, this notice would not have been readily available to Ukraine International Airlines, nor other foreign operators outside of the U.S. Furthermore, Ukraine International Airlines was not the only airline to continue operating after Iran launched missiles against Iraq; eight other aircraft departed Tehran, before the shootdown of PS752.


This report only partially explains why the airspace remained open and why operators continued to fly after Iran had launched missiles into Iraq. It does not explain any of the underlying factors behind why the missiles were launched at PS752, the stated cause of this tragedy. In short, the report says what happened, but doesn’t address the why.

The report indicates that some unspecified safety actions have since been taken to reduce the risk of this happening again. However, the lack of detail means we can’t confirm that these actions will actually reduce the risks to civil aviation operations within Iran’s airspace.

Furthermore, although the AAIB has issued some recommendations, these don’t specifically address the stated cause of this tragic event - the launching of the missiles. 

We know that this has been very difficult for the families. In the end, no safety investigation report can ever bring back those who were lost. And so we must look to what has been learned and what can be done to reduce the risk so that other families don’t have to suffer through this in the future.

We know that states will continue to engage in hostilities with other states, or within their state. And in such a hostile environment, there will always be a risk to civilian aircraft. Innocent lives can be lost. It is the responsibility of the state to reduce those risks.

So the best way to reduce the risk of such tragedies in the future is to firmly apply the lessons learned first, from the downing of Malaysia Airlines Flight 17 and now, from this tragedy.

More needs to be done to protect international civil aviation from operating in conflict zones. In a follow-up report to its investigation into the 2014 downing of Malaysia Airlines flight 17 over Ukraine, the Dutch Safety Board warned (and I quote): “Practice shows that States in which there is an ongoing armed conflict will not implement restrictions for their airspace on their own initiative.”

While ICAO has taken some action it wasn’t enough to prevent this occurrence. Transport Canada is now leading an initiative – Safer Skies – to improve the safety of air travel worldwide by addressing gaps in the way the civil aviation sector deals with conflict zones. Such initiatives offer the best hope for the future to avoid another PS752.

In closing, I know much concern has been expressed about the international protocols that govern the conduct of these very unique types of safety investigations involving military activities, specifically the issue of the state of occurrence investigating itself. Additionally, when a state’s accident investigation agency is not independent of the state aviation authority as required by ICAO, such as Iran’s AAIB, it can affect the credibility of the final report findings and the uptake of resulting recommendations intended to prevent future accidents.

Now that this safety investigation has concluded, the TSB is committed to advocating for a review of the provisions of ICAO Annex 13 to improve the credibility and transparency of such future safety investigations so that families and the public can have confidence in their findings and recommendations.