United States Department of Defense - MIM-104 Patriot , Patriot friendly fire incidents

Patriot was involved in two friendly fire incidents in Iraq, one against a British RAF Tornado GR4A killing both crew, the other against an F/A-18 Hornet killing the pilot.

The Tornado was engaged because the system mistakenly classified it as an anti-radiation missile (ARM), which is a threat typically engaged automatically by the system. This was a result of mistakes on many different levels. First, the path the Tornado was flying in preparation for landing took it directly over the Patriot firing battery. Second, Patriot planners had made the parameters by which the system classifies ARMs too wide, which allowed for a track appearing like the Tornado to be classified as an ARM by the system. Third, the Patriot firing battery had no communications with any higher echelon unit. Fourth, and probably most significantly, the Tornado did not have its IFF transponder on, which could have been an instant indication of the misclassification.

The other incident, on an F/A-18 Hornet, was a Patriot system and operator error resulting from a misclassified TBM. The system engaged the Hornet automatically after the software, in conjunction with the Patriot radar, incorrectly classified the aircraft as a TBM inbound for the Karbala Gap region, where US Army ground forces were currently operating. The Tactical Control Officer and Tactical Director failed to check if the speed and altitude of the track were commensurate with that of a ballistic missile, and not doing so the aircraft was engaged with a PAC-3 missile shortly after firing battery's launching stations were ordered into operation. The aircraft that was flying with the F/A-18 Hornet was almost engaged by another firing battery, until the order was given to disregard.

A third incident occurred when the Radar Warning Receiver (RWR) of a USAF F-16 Falcon incorrectly identified a Patriot battery as an SA-2 battery. At the time, the Patriot battery was protecting the 101st Airborne Division's Headquarters near the Forward Line of Troops (FLOT). The F-16 fired an AGM-88 HARM missile, which struck directly in front of the Patriot Radar Set, incapacitating the unit. The affected Patriot unit was forced to swap its radar set with another unit's in the immediate area. This replacement radar set had not fully undergone a testing period after receiving its PAC-3 upgrade/enhancements, and later the same battery was responsible for the incident of the F/A-18 mentioned above.

A more recent incident occurred on October 15, 2007. A Patriot unit located in Qatar accidentally fired an interceptor while conducting a training exercise. The missile self-destructed in mid-air and some debris landed on a nearby farm. No injuries were reported as a result of the incident.