The extreme U.S. market plunge on May 6, 2010, was commonly called the Flash Crash.
In a matter of minutes, major U.S. equity indexes dropped sharply before recovering much of the loss. The Dow Jones Industrial Average fell nearly 1,000 points, or about 9%, during the session. Many individual securities briefly traded at implausibly low or high prices before normal trading returned.
Investigations linked the event to a combination of market conditions, automated trading, and a large sell order in E-mini S&P 500 futures. High-frequency traders and other systems reacted rapidly, reducing liquidity and amplifying the downward move. Regulators later introduced measures including market-wide circuit breakers and controls for clearly erroneous trades.
The Flash Crash was not a conventional multi-month bear market like 1929 or 2008. Its defining feature was speed: a huge fall and partial rebound within one trading day. The event demonstrated how electronic markets can transmit shocks almost instantaneously.