The event that caused U.S. stocks to plunge briefly on 6 May 2010 was the 2010 Flash Crash.
During the afternoon, major U.S. equity indexes fell rapidly and then recovered much of the decline within minutes. The Dow Jones Industrial Average temporarily lost nearly 1,000 points, an unusually large move for such a short interval. Some individual securities traded at bizarrely low or high prices before normal conditions returned.
Investigations identified a combination of factors, including market stress, rapid automated trading, and the withdrawal or reduction of liquidity. The U.S. Securities and Exchange Commission and Commodity Futures Trading Commission later concluded that a large automated sell order contributed to the instability, alongside broader market conditions.
The episode led to safeguards such as circuit breakers and trading controls. It is distinct from the 1987 crash because the defining feature was its speed and partial intraday reversal, not simply the size of a multi-day decline.