What happened
A military transport aircraft, operating under callsign ULF48, was performing a logistics mission traveling from Tehran to McGuire Air Force Base with a scheduled stop in Madrid. The flight included personnel from both the Iranian and United States militaries. After departing Tehran at 08:20 GMT, the aircraft reached an initial cruising altitude of FL330. While navigating toward the CPL VOR via Castejon, the crew requested a descent to FL100, which was granted at 14:25.
During the flight, the crew reported encountering significant thunderstorm activity and requested a deviation to the left to avoid the weather. At 14:32, Madrid control instructed the aircraft to descend to 5,000 feet and contact approach control. The final communication occurred at 14:33, when the crew acknowledged instructions for a 260° heading while descending. Following this contact, the aircraft type crashed into farmland at an altitude of 3,000 feet MSL. The impact resulted in the total destruction of the airframe and 17 fatalities, with no survivors.
Findings
Investigations into the wreckage revealed that the crash was precipitated by a left wing separation. Evidence suggests that the primary trigger for this structural failure was an explosion caused by the ignition of fuel vapors within the number one fuel tank. While investigators considered whether extreme aerodynamic forces from severe turbulence could have caused the initial structural damage, the evidence more strongly supports the conclusion that an internal explosion initiated the catastrophic sequence.