United Grounds US Flights Due to Tech Glitch, and Resumes With Delays

On August 6, 2025, United Airlines was forced to ground all its US mainline flights following a major technology disruption tied to its Unimatic system—a key platform used to calculate aircraft weight and balance, among other flight-critical functions.

The issue, which began around 6:12 p.m. ET, led to a Federal Aviation Administration (FAA)–mandated ground stop across United’s largest hubs, including Chicago O’Hare, Newark, Denver, and Houston. While flights already airborne were allowed to land, departures were paused nationwide. United Express and regional partners were not directly affected, though delays rippled across the network.

By late evening, approximately 1,100 United flights had been delayed—impacting nearly 35 percent of its scheduled operations—while almost 100 were canceled. The disruption caused wider congestion across US airports, delaying flights on other major carriers as well.

United confirmed that the outage was not the result of a cyberattack. The company resumed operations later the same night after resolving the system failure. As of August 7, flights have restarted, though residual delays are expected throughout the day.

The carrier treats the event as a controllable delay and offers compensation for affected travelers, including hotel accommodations and fee waivers. United’s internal investigation is ongoing, and the FAA monitors recovery efforts.

This marks another high-profile technology-related disruption in American aviation. Similar system outages in recent years have underscored the fragility of digital infrastructure in airline operations. For example, on July 20, 2025, Alaska Airlines experienced a system-wide IT failure, grounding all flights for several hours. The disruption caused over 150 cancellations and delays. In the December 2024 holiday season, a widespread IT outage across airline systems crippled operations, resulting in approximately 7,500 flight cancellations across 200 US airports.

Another reason for disruptions is natural disasters. In late July, Hawaiian Airlines and Alaska Airlines halted all flights to and from the Hawaiian Islands due to a tsunami across the Pacific.

Cover photo by David Syphers on Unsplash.