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.

Yasuj Tower later informed Flight 3704 about the weather condition and mentioned that the final approach path was clear.

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.

[2] According to flight tracking website Flightradar24, the last signal from the aircraft was received just before 05:56 UTC, descending from an altitude of 16,975 feet (5,174 m).

[13] Iranian authorities in neighboring Shiraz and Isfahan province had deployed two of their helicopters to the crash site.

Spokesman from Iran Aseman Airlines initially stated that all 66 passengers and crews on board had been killed in the accident.

[8] Weather conditions at the crash site, including snow and strong winds, were hampering search and rescue services.

[6] The Red Crescent Society announced that a drone would be flown to the area due to the severe weather condition which prevented helicopters to reach the crash site.

The aircraft was obliterated, with large portion of the tail cone, the vertical stabilizer, the rudder and the empennage were found.

[22][23] The head of the country's emergency services said that the recovery of the victims would be challenging due to the adverse weather.

[26] President of Iran Hassan Rouhani ordered Iranian Minister of Roads and Urban Development Abbas Ahmad Akhoundi to lead the investigation.

The French Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) also sent 7 delegations to investigate the crash.

As the aircraft was flying at the altitude, it encountered a series of updraft and downdraft, its airspeed decayed and it then entered a dangerous stall condition.

[2] Data on the weather condition in the area were collected from the Iranian Meteorological Agency and from the airport dispatcher.

The report further stated that the condition in Yasuj would later deteriorate as cumulonimbus clouds were observed in the area, with thunderstorm, rain and hail would also occur.

As the weather condition didn't meet the criteria, the crews of Flight 3704 should have diverted the aircraft to Isfahan in the north or Shiraz in the south.

Mountain wave may pose threat to the safety of a flight as it can lead to severe turbulence, icing, strong windshear, and updraft and downdraft motion to the aircraft.

[2] Further analysis by Iran Meteorological Report stated that an unstable layer, turbulence and freezing level at an altitude of 11,000 ft were predicted.

The lack of communication between the Captain and the First Officer indicated a steep authority gradient phenomenon in aviation, which may be caused due to difference in flying experience.

It was presumed that the crew didn't expect to encounter a mountain wave phenomenon in the area and thus this might have decreased their situational awareness.

[2] The Iranian Civil Aviation Organization published the interim report, with the following:[2][failed verification] The accident was happened due to many chains of considered causes but the human factor had main roll for the conclusion of the scenario.

[30] The search and rescue operation was viewed as too long by some family members, some were angered due to the incompetent handling of the disaster.

On 19 February, more than 100 people reportedly protested outside a government building in Dena Kooh, demanding Iranian officials to step down due to the response on the disaster.

[31] Journalists have speculated that the economic sanctions against Iran which have prevented Iranian airlines from obtaining new planes and spare parts and forced them to operate aging aircraft may have contributed to the cause of the crash.

[32] Iranian judicial authorities and the special committee of the Islamic Consultative Assembly believed that the flight should not have been allowed in the first place, and blamed the Iran Aseman Airlines for the accident.