The 2010 event when US stocks briefly plunged nearly 1,000 Dow points was the Flash Crash.
On May 6, 2010, the Dow Jones Industrial Average fell about 1,000 points, roughly 9 percent, within minutes before recovering much of the loss. Several major US indexes and individual securities experienced extraordinary short-lived price movements.
Investigations identified a combination of factors, including stressed markets, automated trading, high-frequency trading, and a large sell order. The US Commodity Futures Trading Commission and Securities and Exchange Commission concluded that a single trader’s algorithmic activity helped trigger the rapid decline, although market structure amplified it.
The Flash Crash differed from a conventional bear market because its most dramatic losses and recovery occurred within one trading session. It prompted new safeguards, including circuit breakers and clearer procedures for reviewing extreme trades.