Iran said the misalignment of an air defence unit's radar system was the key "human error" that led to the accidental shooting down of a Ukrainian airliner in January, killing 176 people.
"A failure occurred due to a human error in following the procedure" for aligning the radar, causing a "107-degree error" in the system, the Iranian Civil Aviation authority said in a report late on Saturday.
The National has contacted the Canadian and Ukrainian foreign ministries for comment.
The shooting happened on the same night Iran launched a ballistic missile attack against US soldiers in Iraq after the American drone strike that killed Islamic Republican Guard Corps commander Qassem Suleimani in Baghdad.
At the time Iranian troops were bracing for a US counter-strike and appear to have mistaken the plane for a missile.
The report detailed moments when the shooting of Ukraine International Airlines Flight 752 could have been avoided.
The report said the surface-to-air missile battery that hit the Boeing 737-800 had been relocated and was not properly reoriented.
Those manning the missile battery could not communicate with their command centre, misidentified the civilian flight as a threat and opened fire twice without approval from ranking officials, the report said.
"If each had not arisen the aircraft would not have been targeted," the report said.
Canada and Ukraine have demanded for months that Iran, which does not have the technical means to decode the plane's black boxes, send them abroad so their contents can be analysed.
In late June, France's Accident Investigation Bureau said Iran had "officially requested technical assistance" to retrieve the data.
Work on the cockpit voice and flight data recorders "should begin on July 20", the French agency said.
In early July, Canada announced it had reached an agreement in principle with Iran to launch negotiations on compensation for the families of foreign victims of the accident.
