February 6, 2017: The United States has agreed to sell $1.45 billion of the latest version of the PAC-3 Patriot anti-missile missile (Advanced Capability-3) to foreign users Qatar, South Korea, Saudi Arabia, Taiwan, and the UAE (United Arab Emirates). This sale includes upgrade kits (MSE or Missile Segment Enhancement) for many of the older PAC-3s these countries have. The PAC-3 and the Patriot air defense system is one of the least expensive, and combat proven, ABMs (anti-ballistic missile) available. As more bad actors (Iran, North Korea, China) develop or expand arsenals of ballistic missiles for use with conventional warheads, more of their neighbors seek an affordable and proven solution to the threat.

Development of the PAC-3 MSE version of was completed in 2013. The new rocket motor and other new or redesigned components boost the PAC-3s range to over 35 kilometers and altitude to over 36,000 meters (112,000 feet, nearly 50 percent more than earlier PAC-3s). The PAC-3 MSE is heavier than previous PAC-3s, and this will reduce the number that can be carried on a launcher from 16 to 12.

March 25, 2003: Patriot was shooting down ballistic missiles before it had a chance to shoot down an aircraft. That happened in March 2003 when a British Tornado fighter was shot down by a Patriot missile over Iraq. That occurred because of a problem with the IFF (Identification, Friend or Foe) beacon every combat aircraft carried. The IFF broadcasts a coded message to friendly aircraft and anti-aircraft systems. Early on it became obvious that 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. Despite this tragic error, Patriot became one of the few air defense systems to endure enough combat zone use to encounter this sort of problem and have it solved. When it comes to weapons, experience is a major factor.

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 (5,000 kilometers/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 experience in the 1990 Persian Gulf War showed that this approach had more promise than performance. In part that was because it was only in 1988 that 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 1990 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 were used in Iraq in 2003.

When it was introduced in 1981 the Patriot missiles originally had a shelf life of 15 years but several rounds of upgrades and refurbishments enable many of the 100,000 missiles built since the 1980s to be kept in service for another decade or more. The refurbishment also includes using new technology to accurately measure age-related decay in many components. This is an important aspect of being able to extend shelf-life in missiles and aircraft. This refurbishment is how many missiles built over two decades ago turned into MSE versions.

The current version of the original Patriot missile design (MIM-104E PAC 2) cost $2 million each and can be used against aircraft and some missiles. The smaller PAC-3 (MIM-104F) anti-missile missile can only be used against missiles and can cost up to $3 million each. PAC-3 entered service in 2002. While each Patriot launcher, loaded with PAC-3 missiles, can only defend against ballistic missiles approaching within its shorter range (20-35 kilometers), the Patriot radar can detect targets out to a hundred kilometers. Two PAC-3 missiles are fired at each incoming ballistic missile, to increase the probability of a hit. The PAC-3 missile has its own radar and uses it to track the incoming warhead and execute a collision course.