The British Tornado fighter shot down by a Patriot missile on March 24th was the first aircraft ever downed by a Patriot. Development of the Patriot began in the early 1960s as the "SAM-D." The usual bureaucratic delays, and the rapid appearance of new technologies, slowed the system up, and it didn't enter service until 1982. But even then, new electronic capabilities made it possible to adapt the Patriot to anti-missile work. The main requirement here was data processing speed, because a ballistic missile warhead returns to earth at high speed (over 3,000 miles an hour) and you have to be fast to get a shot off.  Why try to make the Patriot an anti-missile missile? For the simple reason that U.S. anti-aircraft have had few targets since World War II. The U.S. Air Force has been supreme in the air, and a more likely foe would be ballistic missiles. The Gulf War showed that this approach had more promise than performance. So in 1988,the first Patriot anti-missile missile (PAC-1) entered service. Work continued on the anti-missile capabilities, and in 1990, PAC-2 missiles entered service. These were used during the 1991 Gulf War. The Iraqi SCUDs, modified (with a lengthened fuselage to accommodate more fuel) broke apart when they reentered the atmosphere and presented the waiting Patriot radars with several objects, only one of which was the warhead. Based on that experience, more improvements in accuracy, discrimination (telling junk from warheads)  and lethality (ability to destroy the warhead), resulted in the PAC-3 missile, which entered service in 1995. Improved PAC-3 missiles entered service in 2001. Both versions are  being used in Iraq in 2003. The problem with shooting down the Tornado was most likely related to IFF (Identification, Friend or Foe). Every warplane carries an IFF beacon, the broadcasts a coded message to friendly aircraft and anti-aircraft systems. Either the IFF beacon in the Tornado, or the IFF equipment with the Patriot fire control system, was faulty. This made rapidly approaching Tornado appear on the radar as a hostile aircraft. The fire control officer had second to either fire at the apparently "hostile" aircraft, or risk an air attack on friendly forces.