Ukrainian authorities submitted dozens of comments to Iranian investigators, many highly critical, regarding multiple aspects of the inquiry into last year’s fatal missile attack on a Boeing 737-800 shortly after take-off from Tehran.

The Iranian Civil Aviation Organisation has formally attributed the destruction of flight PS752 to the misidentification of the jet as a hostile target by an air defence unit.

This unit had been locally relocated “according to the tactics” of such mobile air defence systems, says the inquiry, and had been placed on standby until it was made operational at 06:07 on the morning of 8 January 2020, about 5min before the 737 took off from Imam Khomeini airport.

But during the relocation the unit’s heading changed, owing to the operator’s “failure in conducting north realignment properly”, introducing a 105° error in the calculated bearing of detected targets.

When the unit detected the 737 the operator transmitted the details over a co-ordination centre communication network, but the message was not relayed to the centre, says the inquiry.

“It had not been recorded in the recorded messages of the co-ordination centre,” it adds. “Without receiving a response from the co-ordination centre, the operator came to the conclusion that the observed target was a threat and fired a missile.”

Although the radar-guided Tor-M1 surface-to-air weapon launched by the unit detonated and caused “cascading” damage to the aircraft, the air defence unit “observed the continuity of the detected target trajectory” and fired a second missile 30s after the first.

Recorded data in the unit indicated this second missile strike failed, but the aircraft subsequently crashed with the loss of all occupants – including the three cockpit crew who had survived the initial missile detonation.

UIA 737 wreckage-c-Iranian CAO

Source: Iran Civil Aviation Organisation

Wreckage of the UIA 737 after it was shot down by surface-to-air missiles

“Mitigating measures and defence layers in risk management proved to be ineffective due to the occurrence of an unanticipated error in threat identification,” says the inquiry, adding that this meant the flight’s safety was not protected from the alerted defence forces.

Ukrainian investigation authority NBAAI submitted dozens of comments about the draft report to the Civil Aviation Organisation, requesting that they be appended to the final one.

The inquiry says any comments which enhanced the accuracy and effectiveness of the final report have been included, but it has also listed some 100 comments from NBAAI which were not adopted.

These include critical remarks arguing that the cause was not the detonation of the missile but the attack on the aircraft, and that the inquiry “ignores” systemic failure on the part of the Iranian state – including lack of control of defence systems and non-observance of duties by officials.

Ukraine’s comments dismiss as “incorrect, and certainly not accurate” the statements that the inquiry was conducted in accordance with ICAO’s Annex 13 procedures.

“The accident scene and all the evidence were not preserved, the on-board recorders were not decoded at the first opportunity and the decoding thereof was unreasonably delayed for more than six months,” the NBAAI’s remarks add.

UIA 737 winglet debris-c-Iran CAO

Winglet debris located at the crash site

Its comments even describe some of the factual information in the report as “incorrect and far-fetched” and says they “do not correspond with the evidence available”.

The authority is also not satisfied with the finding that the second missile did not strike the 737.

NBAAI accuses the inquiry of failing to investigate a number of aspects fully, particularly in regard to the operation of the air defence system and attempts to identify the aircraft before the missiles were fired, and points out that the conclusions do not reference any violation in the Iranian civil-military air traffic management system.