The sudden May 6, 2010 plunge and rapid rebound in U.S. financial markets is called the Flash Crash.
During the afternoon of May 6, major U.S. equity indexes dropped extremely quickly, with the Dow Jones Industrial Average losing roughly 1,000 points within minutes before recovering much of the decline. Prices in some individual securities moved to implausible levels as liquidity temporarily disappeared.
Investigations found that automated trading, market fragmentation, and an unusually large sell order contributed to the event. The U.S. Securities and Exchange Commission and the Commodity Futures Trading Commission later described a chain of interactions rather than a single simple cause.
The episode led regulators and exchanges to strengthen safeguards, including circuit breakers and rules for handling clearly erroneous trades. It was not a conventional multi-month bear market like the crash of 1929.