The 2010 event that briefly sent U.S. stock indexes into an extreme intraday plunge was the Flash Crash.
On May 6, 2010, the Dow Jones Industrial Average dropped about 1,000 points, or nearly 9%, within minutes before recovering much of the loss. Some individual securities traded at bizarrely low or high prices during the disruption.
Investigations linked the episode to interactions among high-frequency trading, algorithmic orders, and a large sell order in an already nervous market. The event differed from a conventional crash because its most dramatic movement was exceptionally rapid and partly reversed the same day. Regulators subsequently strengthened market-wide circuit breakers and introduced mechanisms such as single-stock pauses.