Key Metrics
18.38
Heat Index-
Impact LevelMedium
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Scope LevelNational
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Last Update2025-08-07
Key Impacts
Negative Impacts (4)
Event Overview
Airlines' dependence on critical computer systems for flight safety and load management is underscored as a technical failure disrupts nationwide operations. The incident highlights vulnerabilities in operational infrastructure and the cascading effects of system outages on scheduling, passenger management, and regulatory compliance. Distinctions between impacted mainline and unaffected regional services reveal tiered resilience in aviation networks.
Collect Records
United Airlines Grounds Mainline Flights Nationwide Due to Weight and Balance System Outage
On Wednesday, United Airlines temporarily grounded all its mainline flights across the United States due to a widespread technology issue affecting the airline's weight and balance computer system, known as Unimatic. The issue began at approximately 6:12 p.m. Eastern Time and was resolved within a few hours. The outage did not affect United Express flights, and aircraft already airborne were allowed to continue to their destinations.
According to United Airlines and the Federal Aviation Administration (FAA), the problem caused significant disruption, with more than 1,000 flights delayed and over 40 flights canceled, according to flight tracking data from FlightAware. Passengers across major hubs, including Newark, San Francisco, Chicago, Denver, and Houston, experienced lengthy delays. At Chicago O'Hare Airport, some passengers were stranded on planes on the tarmac for extended periods.
United Airlines confirmed the issue was unrelated to recent industry cybersecurity events and stated it was not caused by a cyberattack. The company explained, "Due to a technology issue, we are holding United mainline flights at their departure airports. We expect additional flight delays this evening as we work through this issue. Safety is our top priority, and we'll work with our customers to get them to their destinations." The FAA acknowledged, "We're aware United experienced a technology issue disrupting their operations. Some delays may continue as they work through the recovery process."
Passengers were notified of the outage and given updates as operations resumed. In some cases, United offered to pay for overnight hotel stays and rebook tickets for travelers whose flights were delayed or canceled. The specific technical cause of the Unimatic weight and balance system failure was not disclosed. United Airlines reported that normal operations were being restored, but residual delays were expected as they worked through the backlog.