On Wednesday evening (August 6), United Airlines temporarily grounded all of its commercial flights across the United States. The company blamed a system outage.
The disruption delayed or canceled more than 150 flights out of San Francisco International Airport (SFO), one of United’s hubs.
The Federal Aviation Administration (FAA) identified the cause of the interruption as a failure in United’s “weight and balance” calculation system.
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The weight and balance system is a critical component in aircraft operations that ensures proper loading for safe takeoff. Without reliable output from this system, aircraft cannot be cleared for departure.
A technology malfunction delayed or canceled more than 150 United Airlines flights.
Image source: Shutterstock
Delays affect United Airlines but not United Express
According to the FAA, the outage triggered a nationwide ground stop that affected United’s mainline flights but not its regional United Express flights.
While aircraft already in the air continued operating as scheduled, departures from major hubs — including Chicago O’Hare, Newark, Denver, and Houston — were held on the ground.
At SFO, flight tracking data indicated seven outbound United flights were canceled, while 152 were delayed.
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As for inbound flights, four arrivals were canceled and 136 were delayed. Nationwide, United delayed more than 820 flights and canceled 23, according to FlightAware, representing approximately 28% of its daily operations.
United Airlines responds to flight delays
In a public statement, United Airlines said:
“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 system returned to normal within approximately 60 minutes, but operational disruptions continued into the evening due to aircraft and crew displacements, gate congestion, and backlog clearance.
United says disruption not related to a cybersecurity breach
United confirmed that the outage was not the result of a cybersecurity breach, but rather an internal system malfunction.
This event marks the second major technology-related grounding in the U.S. airline industry within a matter of weeks.
In July, Alaska Airlines halted all operations for several hours due to a similar malfunction in its weight and balance system — a repeat of an incident it experienced the previous year.
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While often overlooked outside technical circles, the weight and balance system is mission-critical. It ensures an airplane is safely loaded and properly balanced for flight by calculating the total weight and how it’s distributed throughout the aircraft.
Since United has a tightly scheduled network, a failure of this magnitude can easily cause a widespread disruption.
What United Airlines passengers can do
United is waiving fees for any passenger whose flights have been delayed or canceled due to the outage. The airline also noted that its operations team is actively working to reposition aircraft and flight crews to normalize service, though full recovery may extend into Thursday.
The FAA has not announced any investigations or enforcement actions as of this writing and is monitoring the situation.
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