Iran has invited manufacturer Boeing to take part in the investigation into the crash of a Ukrainian Airlines plane minutes after it left Imam Khomeini airport in Tehran.
The country's authorities has so far refused to hand over the plane's black box, which may contain vital details about the plane's final moments, to the plane manufacturer.
It comes as Canada's Prime Minister Justin Trudeau has demanded answers after 63 Canadian citizens lost their lives in the crash.
The intelligence services of several Western nations have declared their belief that Iran accidentally shot down the aircraft, killing all 176 people on board.
