Flight History
The aircraft was conducting a military logistic flight from Tehran, Iran, to McGuire Air Force Base in the United States, with a stop in Madrid, Spain. It carried Iranian and US officers. The flight departed Tehran at 08:20 GMT and climbed to a cruising altitude of FL330. After contacting Madrid control, the crew received clearance to proceed via Castejon to the CPL VOR.
Accident Sequence
At 14:25, the flight was cleared to descend to FL100. Five minutes later, the crew advised Madrid that they were diverting left due to thunderstorm activity. At 14:32, Madrid cleared the aircraft to 5,000 feet and directed it to contact Madrid approach control. The crew contacted approach control at 14:33, reporting significant weather ahead and requesting vectors around it. The last radio communication occurred when the crew acknowledged a heading of 260° and stated they were descending to 5,000 feet. The aircraft subsequently crashed in farmland at an elevation of 3,000 feet msl. The left wing had separated from the aircraft before impact. The aircraft was destroyed entirely, and all 17 occupants were killed.
Investigation and Probable Cause
Investigators analyzed all available evidence and concluded that the most probable sequence of events began with an ignition of fuel vapors in the No. 1 fuel tank. This explosion caused multiple structural failures and ultimately the separation of the wing. Damage to the structure around the tank provided positive indications of an explosion. The possibility that the explosion resulted secondarily from structural failure due to excessive aerodynamic forces during high-velocity gusts and turbulence was considered but deemed less supportable given the evidence and the rarity of such environmental conditions.