The right engine had been failing for months. In April 2014 alone, two engine failures were recorded during flights to Bandar Abbas. On April 28, the failure warning light illuminated briefly. Inspection on April 29 found corrosion on the left engine's compressor blade, but the right engine continued to fly. Three days before the crash, on August 7, during a flight from Tabriz to Isfahan, violent shaking was recorded on the right engine. The flight data recorder captured it. A sensor was replaced, but investigators later determined it was improperly installed. The aircraft's electronic engine control system, known as SAY-2000, had a documented history of causing engine failures at rates above acceptable levels. Software modifications had been attempted. They had not worked.

Flight 5915 departed Tehran Mehrabad's Runway 29L at 9:22 a.m. on August 10, 2014, bound for Tabas in South Khorasan province. It carried 42 passengers, including six children, and a crew of six. The investigation would reveal a cascade of configuration errors. The aircraft was overloaded by 2,666 kilograms, partly because the Aircraft Flight Manual was confusing enough that the crew overestimated the maximum takeoff weight by 190 kilograms, and partly because 500 kilograms of excess fuel had been loaded. The stabilizer trim was set incorrectly. The rudder trim was not centered. The flaps were five degrees short of their required setting. The crew attempted takeoff at 219 km/h instead of the required 224 km/h.

During the takeoff roll, the SAY-2000 system malfunctioned, cutting fuel to the right engine's combustion chamber. Two seconds after the engine lost power, the captain pulled the aircraft into the air, even though rotation speed had not been reached. The crew recognized the engine failure within five seconds. They discussed it. Nine seconds after the failure, the captain re-emphasized the problem. But neither pilot pressed the right propeller feather button. Fourteen seconds in, the copilot reported the failure to air traffic control. The aircraft reached a peak speed of 224 km/h, then began to slow. It climbed to a maximum altitude of 40 meters. Then it stalled. By the time the propeller was feathered at the seventeen-second mark, recovery was impossible. The aircraft struck a boulevard 1.6 kilometers from the end of the runway.

The aircraft crashed onto a boulevard near Azadi Stadium in western Tehran. Emergency responders were notified immediately, but miscommunication and poor coordination delayed their arrival at the crash site. Eleven passengers were pulled alive from the wreckage. Three later died in hospital, leaving eight survivors. Thirty-four passengers and all six crew members perished. Three people on the ground suffered burns. The investigation concluded that no single factor caused the crash. An unreliable engine control system, an ambiguous flight manual, an overloaded aircraft, incorrect trim settings, premature rotation, and delayed propeller feathering all converged in those seventeen seconds between engine failure and the point of no return. Each error alone might have been survivable. Together, they were not.