Designed in the late 1970s as an anti-aircraft weapon, the Patriot was modified in the mid-1980s to defend against ballistic missiles as well.
According to Gulf War - A Comprehensive Guide to People, Places & Weapons by Col. Walter J. Boyne, U.S. A.F. (RET) Signet, 1991, quoted at Frontline's Gulf War (I) site.
And we come full circle:
The Royal Air Force has confirmed that a U.S. Patriot missile shot down a British Tornado fighter earlier Sunday. It was the first reported incident of friendly fire since the war began. The two-man crew are reported as missing. The plane was returning from an operational mission when it was shot down near the border with Kuwait.
Not sure about that "first reported incident of friendly fire" line, but I haven't been following events as closely as I could.
Last time around, during the wait for "hostilities to begin" as the expression went, it seemed every day brought news of another fatal fuck-up from within our own ranks. The cynic in me said all the Iraqis really needed to do was sit around playing Uno and we'd manage to wipe ourselves out without any assistance from them.
Of course, once hostilities did begin, things got worse. "[F]riendly fire accounted for almost a quarter of the U.S. fatalities in the 1991 Persian Gulf war," according to CNN.com. "45 percent of American fatalities" is the figure given at TechTV, and like the Patriot's success rate, I'm confident you can find any numbers you want, depending on when they were released and who did the analysis.
You know. Lies, damned lies and statistics.
An update of minor note, from Warren Ellis:
It is entirely possible that more Brits have been killed by Americans than by Iraqis in Gulf War 2 thus far.
He was writing of reporter Terry Lloyd, but you get the idea.