During the 2010 Flash Crash, about how long did the sharpest market plunge last?

The sharpest plunge of the 2010 Flash Crash lasted about 36 minutes.

On May 6, 2010, major U.S. stock indexes suddenly dropped and then recovered much of the loss within minutes. The Dow Jones Industrial Average fell nearly 1,000 points, roughly 9%, before rebounding. The extraordinary speed distinguished the event from a conventional bear market.

Investigations concluded that high-frequency trading and a large sell order in E-mini S&P 500 futures interacted in destabilizing ways. The U.S. Securities and Exchange Commission and Commodity Futures Trading Commission described a feedback loop in which liquidity vanished and automated orders intensified price movements.

The crash exposed weaknesses in market safeguards and in the links among exchanges, futures markets and electronic trading systems. Regulators later introduced or strengthened mechanisms such as single-stock circuit breakers and market-wide trading pauses.