What was the name of the 1989 crash in which U.S. program trading intensified a late-session sell-off?

The 1989 crash in which U.S. program trading intensified a late-session sell-off was the Friday the 13th mini-crash.

It occurred on Friday, October 13, 1989, when the proposed leveraged buyout of United Airlines' parent company failed. The news triggered heavy selling, particularly in shares connected to the deal, and broader U.S. markets fell sharply during the session. The Dow Jones Industrial Average declined 190.58 points, or about 6.91%, in one of its largest one-day percentage losses at that time.

Program trading and portfolio-insurance strategies were widely discussed as forces that could amplify declines by generating automatic or rules-based selling. The event was smaller and shorter than the 1987 crash, so it became known as a mini-crash rather than another Black Monday.

The episode is sometimes confused with the October 1987 crash because both involved computerized trading and sudden market stress. They were separate events, occurring nearly two years apart and involving different immediate triggers.