The aircraft went off radar midflight from Tehran to Yasuj, some 20 minutes after take off, local media reported.
The plane disappeared from radar in a mountainous area. The search and rescue operation is hampered by bad weather, preventing helicopters from landing, Iran’s Press TV reports.
Everyone on the flight was killed, Aseman Airlines spokesman Mohammad Taghi Tabatabai told state TV, adding that the plane had crashed into Mount Dena, about 440 meters (1,440 feet) tall. Originally, 66 fatalities were reported, including one child, and six crew members, but IRNA news agency has since reported that one of the passengers did not board the flight.
The missing plane is an ATR 72, a French-Italian short-haul regional airliner, which was introduced in the late 1980s. Iran signed a contract to buy 20 ATR 72s in 2016 with an option for 20 more, and received the first batch last year. The fleet of Iran Aseman Airlines, however, is older, with aircraft delivered between 1993 and 2009, according to a planespotters.net database.
Semirom is located about 80km north of Yasuj, the capital of the southwestern Kohgiluyeh and Boyer-Ahmad Province.