Date: July 3rd, 1988
Type: Airbus A.300B2-203
Registration: EP-IBU
Operator: Iran Air
Where: Srait of Hormuz
Report No.: Not Available
Report Date: -
Pages: -

This is not an accident investigation report.

Flight IR451 arrived at Bandar Abbas from Tehran at 05.10h UTC. At 06.47h the aircraft took off again as flight IR655 bound for Dubai. Two minutes later, the crew reported leaving 3500ft for FL140 on Airway A59, estimating MOBET at 06.53. At 06.54:00 UTC the aircraft passed MOBET out of FL120. Nothing more was heard from IR655. At 06.54:43 two surface-to-air missiles struck the aircraft. The tail and one wing broke off as a result of the explosions, causing the aircraft to crash into the sea out of control. The missiles were fired by the US Navy cruiser USS Vincennes. The Vincennes was operating in the area to protect ships in the area, together with the frigates USS Elmer Montgommery and USS John H. Sides. Due to increasing tension in the area (May 17, 1987 an Iraqi Mirage attacked the USS Stark) all aircraft in the area had to monitor 121.5 Mhz (International Air Defence - IAD radio frequency). At about the time the Airbus took off, the radar picked up a brief IFF mode 2 response, which led to the mistaken identification of the Airbus as a hostile F-14 aircraft. The USS Vincennes issued 7 challenges on the Military Air Distress (MAD) frequency 243 MHz, adressed to 'Iranian aircraft', 'Iranian fighter' or 'Iranian F-14'. These messages were followed by three challenges on the IAD. A number of AEGIS radar operators misread the displays and reported that the incoming plane was descending with an increasing speed. This fact, and the fact that the aircraft didn't respond to the challenges led to the decision to launch two missiles against the perceived hostile target. It remains uncertain whether the IR655 flightcrew (only able to monitor the IAD, not the MAD frequencies) would have been able to rapidly identify their flight as the subject of the challenges made by the USS Vincennes.
Source: ICAO Adrep Summary 3/88 (#1); ICAO Circular 260- AN/154 (27-51); Aviation Disasters / D. Gero (200- 202)