The sudden U.S. stock-market plunge on May 6, 2010, was the Flash Crash.
During the afternoon, major U.S. indexes fell extremely quickly before recovering much of the decline. The Dow Jones Industrial Average briefly lost nearly 1,000 points, an unusually large move for a single session at that time. Individual securities also traded at wildly different prices, including some transactions far below their surrounding market levels.
Investigations found that high-frequency trading and algorithmic order interactions amplified an existing period of market stress. A large automated sell order in E-mini S&P 500 futures was identified as an important contributor, although the event resulted from several interacting conditions rather than one simple cause.
The episode led exchanges and regulators to improve safeguards, including single-stock circuit breakers and later market-wide mechanisms. It was not the same as the 1987 crash: the 2010 event unfolded and largely reversed within minutes, while 1987 produced a lasting one-day collapse.