Issue Limited To UAL, No Effect On Other Airlines Or Flights

United Airlines said it had resumed operations after all of its mainline flights were grounded for several hours in the evening of August 6, 2025. The technical issues was limited to the carrier’s mainline flights, those operated directly by United, and there was no stoppage of any other airline, charter, or private flights.

Ground stops were issued at all major United hubs including Newark, Denver, Houston, and Chicago, and San Francisco. The problem was related to its Unimatic system that houses information about each flight and feeds it to other systems such as those that calculate weight and balance and track flight times.

United Airlines wrote in a post on its Instagram account, "We are working with customers to get them to their destinations after a technology disruption on Wednesday evening. The underlying technology issue has been resolved, and, while we expect residual delays, our team is working to restore our normal operations."

U.S. Secretary of Transportation Sean P. Duffy said that United CEO Scott Kirby briefed him and said the technical issues was “specific to United's operations" and was "unrelated to the broader air traffic control system."

Mainline flights are those operated by United using its own aircraft and crews, and include Boeing 737, 757, 767, 777, and 787 aircraft as well as Airbus A319 and A320 models.

United responded to travelers posting on social media by acknowledging the issue saying, "We're aware of the system error at this time and are working on a fix to have you on your way as soon as possible. We understand that this disruption has caused frustrations during your travel and appreciate your continued patience."

United said it would pay or compensate customers for any expenses incurred such as hotels, where applicable.

FMI:  www.united.com/