Iran Aseman Airlines Flight 3704

Iran Aseman Airlines Flight 3704 was a scheduled Iranian domestic passenger flight from Iranian capital Tehran Mehrabad International Airport to Yasuj in southwest Iran. On 18 February 2018, during its approach to Yasuj, the aircraft serving the flight, an ATR 72-212 operated by Iran Aseman Airlines, crashed into Mount Dena in the Zagros Mountains near Noqol village in Semirom county, Isfahan Province. All 66 people on board, including 60 passengers and 6 crew members, were killed.

According to the final report, which was published on 15 June 2020 by the Iranian Civil Aviation Organization (CAO), the accident was caused by multiple factors, with pilot error considered as the main cause. The investigation showed that the crew decided to continue to Yasuj despite deteriorating weather conditions in the area. During its approach, the crew elected to descend below the minimum altitude. The resulting bad weather caused the aircraft to stall. The crew failed to recover the aircraft from the stall and the aircraft crashed onto the mountain.

The crash highlighted the danger of mountain waves and the aviation industry's lack of awareness of the issue. The Iranian CAO published several recommendations to ICAO and the European Aviation Safety Agency to address the hazard that a mountain wave may pose to the safety of a flight. Subsequently, the crash also led to changes of the weather training programs for airliners in Iran.

Accident

The aircraft was operating a domestic scheduled passenger flight from Iranian capital Tehran Mehrabad International Airport to Yasuj Airport in Yasuj, the capital of Kohgiluyeh and Boyer-Ahmad Province in southwest Iran. The flight was supposed to take about 50 minutes. It took off from Tehran with 60 passengers and 6 crew members on 18 February 2018 at about 04:35 UTC.

At 05:49 UTC, as Flight 3704 approached Yasuj, the flight crew asked the meteorological information in Yasuj. Yasuj Tower later informed Flight 3704 about the weather condition and mentioned that the final approach path was clear. The flight later was cleared to descent to FL170 by Tehran and was handed over to Yasuj on 05:53 UTC.

The crew stated that they would continue the approach with FL150. At 05:55, the crew reported that they were 25 miles from the destination airport. Yasuj Tower then told the pilot about the updated condition in Yasuj, stating that clouds were slowly moving to the south. Four minutes later, Yasuj asked the flight again and the crew responded that they failed to receive the signal of Distance Measuring Equipment (DME) from their navigational device. The crew then checked about the weather condition in the area again.

At 06:04 UTC, Yasuj Tower lost communication contact with Flight 3704. Attempts had been made to re-establish communication with the aircraft but failed.

According to flight tracking website Flightradar24, the last signal from the aircraft was received just before 05:56 UTC, descending from an altitude of 16975 ft.