What happened
On the evening of the accident, an Iran Air flight, service IR2CL, departed Mashhad Airport for Tehran-Mehrabad Airport. The aircraft was carrying 120 passengers and a crew of eight. The flight schedule followed a period of significant disruption in Iranian airspace caused by an air traffic controller strike that had ended only hours prior to the departure.
At approximately 18:52LT, controllers at Tehran-Mehrabad Airport provided clearance for a direct approach toward runway 29. During the descent, the flight crew was directed to perform a 360-degree turn to intercept the Varamin non-directional beacon. As the aircraft progressed through its approach, the co-pilot noted that the VORTAC was providing an incorrect radial course; however, no corrective action was taken following this observation.
While descending in darkness amidst heavy snow and fog, the Airbus A300 (implied by context of IR291/type) struck a slope within the Alborz Mountain Range. The impact caused the aircraft to disintegrate. Search teams located the wreckage in snow-covered terrain roughly 29 km north of Tehran several hours later. There were 128 fatalities and no survivors.
Findings
Investigations into the crash identified that the accident was a result of controlled flight into terrain. This was exacerbated by the fact that the ground radar was not functioning and the instrument landing system (ILS) for runway 29 was inoperable. Additionally, the flight was operating under challenging meteorological conditions characterized by low visibility, night, and active snowfall.