United Airlines experienced a nationwide departure halt due to a software glitch triggered by a recent software update. The glitch temporarily disrupted one of the largest carriers in the United States on a busy travel day. Federal officials noted that United crews were unable to contact airline dispatchers using normal communication channels, but they emphasized that this was not a cybersecurity issue.

The Federal Aviation Administration (FAA), responsible for managing the nation’s airspace, confirmed that United Airlines had requested a nationwide departure stop. However, the FAA clarified that the issue was specific to United Airlines and its subsidiaries. Fortunately, the ground stop did not affect planes already in the air, limiting its impact.

The interruption lasted slightly over an hour, and by late afternoon on the East Coast, United Airlines had canceled only seven flights, a relatively low number compared to its average of around 16 cancellations per day during the busy Labor Day weekend. However, more than 350 United flights experienced delays, amounting to 13% of the carrier’s schedule, significantly higher than its competitors American, Delta, and Southwest.

It’s worth noting that Southwest Airlines had faced a similar outage in April, grounding all departing flights for an hour and causing over 2,000 flight delays. The FAA had also briefly halted all U.S. departures in January due to a system failure that alerted pilots to safety hazards, attributing the issue to a contractor’s accidental deletion of files during synchronization with the backup system.

Transportation Secretary Pete Buttigieg, who has previously criticized airlines for flight-related problems, said that the FAA was investigating the cause and scope of the issue.

As news of the ground stop spread, shares of United Airlines Holdings Inc. fell by 2.5%. The incident serves as a reminder of the critical role technology plays in modern air travel and the potential impact of software-related issues on airline operations.