(Wikipedia) - On January 21, 1980, an Iran Air Boeing 727-86 was making a domestic flight from Mashhad Airport to Tehran Mehrabad Airport in Iran. At 19:11 local time, the aircraft, registered as EP-IRD, collided with the Alborz Mountains, 29 kilometers north of Tehran, during its approach to Tehran-Mehrabad runway 29 in foggy and snowy weather conditions. All 8 crew members and 120 passengers died in the accident, and the plane was destroyed. At the time, it was the deadliest aircraft disaster in the Iranian history.
Investigators concluded that the probable cause of the crash was inoperable landing system and ground radar.
Statistics related to this accident:
32nd loss of a Boeing 727
6th worst accident involving a Boeing 727 (at the time)
16th worst accident involving a Boeing 727 (currently)
worst accident in Iran (at the time)
4th worst accident in Iran (currently)