Patriot's Fatal Error

Sometimes, the cost of a software glitch can't be measured in dollars. In February of 1991, a U.S. Patriot missile defense system in Dhahran, Saudi Arabia, failed to detect an attack on an Army barracks. A government report found that a software problem led to an "inaccurate tracking calculation that became worse the longer the system operated." On the day of the incident, the system had been operating for more than 100 hours, and the inaccuracy "was serious enough to cause the system to look in the wrong place for the incoming Scud," said the General Accounting Office report. The attack killed 28 American soldiers.

Prior to the incident, Army officials had fixed the software to improve the Patriot system's accuracy. That modified software reached Dhahran the day after the attack.

Shown here is a Scud missile that got through the defenses near Tel Aviv, Israel on February 9, 1991.