March 9, 2020, marked the first major U.S. stock-market circuit-breaker halt during the COVID-19 crash.
The S&P 500 fell more than 7% shortly after trading opened on March 9, 2020. That decline triggered a Level 1 circuit breaker, which halted trading on major U.S. exchanges for 15 minutes. The mechanism was designed to give investors time to assess rapidly changing information rather than react continuously to panic.
The immediate shock included the spread of COVID-19, growing expectations of economic shutdowns, and a collapse in oil prices after a dispute between Saudi Arabia and Russia. U.S. markets experienced additional circuit-breaker halts on March 12, March 16, and March 18.
The halt was not the same as the temporary plunge known as the Flash Crash of May 6, 2010. That earlier event involved a rapid intraday collapse and recovery, while the 2020 halts occurred during a prolonged global pandemic-related sell-off.