The automated-trading plunge in U.S. markets on May 6, 2010, is commonly called the Flash Crash.
During the afternoon of May 6, major U.S. equity indexes fell rapidly and then recovered much of the loss within minutes. The Dow Jones Industrial Average briefly dropped by nearly 1,000 points, at that time its largest intraday point decline, before rebounding. Many individual securities also experienced extreme temporary price movements.
Investigations concluded that high-frequency trading and the interaction of automated orders contributed to the sudden instability. The U.S. Securities and Exchange Commission and Commodity Futures Trading Commission later described a large sell order in E-mini S&P 500 futures as an important trigger within a market already under stress.
The Flash Crash is distinct from a conventional prolonged bear market: its defining feature was the speed of the fall and recovery. The event led U.S. regulators and exchanges to introduce or strengthen safeguards, including circuit breakers and rules for handling clearly erroneous trades.