Four countries have called on Iran to submit to arbitration and be held accountable for the downing of Ukrainian Airlines Flight PS752.
The Boeing aircraft was hit by two missiles after leaving Tehran for Kyiv on 8 January 2020, killing all 176 people on board.
Canada, Ukraine, Sweden, and the UK have urged Tehran to settle a dispute, nearly three years after the incident.
The four countries say they are taking "concrete action" against Iran under the 1971 Montreal Convention, which regulates civil aviation offences.
They have accused Iran's Islamic Revolutionary Guard Corps of having "unlawfully and intentionally" downed the plane.
If Iran does not agree to arbitration within six months, the case could be sent to the UN's International Court of Justice in the Hague.
Iranian armed forces only admitted three days later that they had shot down the plane "by mistake" amid heightened tensions with the United States.
Countries have long been negotiating with Iran to obtain compensation for the families of the victims. At least 85 of the people on board PS752 were Canadian citizens or residents
"Those who lost loved ones in the downing of PS752 deserve justice," Canadian foreign minister Melanie Joly wrote on Twitter.
"We have taken an important step to advance our pursuit of that justice at the international level this week and will continue to work together to hold Iran accountable for this tragedy."
In December 2020, Iran said it was prepared to pay "150,000 dollars or the equivalent in euros" to each of the families of the flight victims.