United Airlines temporarily halted all mainline departures across the United States on Wednesday evening after a technology failure disabled the carrier’s flight-information platform. The Federal Aviation Administration confirmed that United requested a nationwide ground stop at about 8:15 p.m. Eastern time and began releasing flights roughly three hours later. The carrier said the malfunction originated in its Unimatic system, a decades-old database that feeds critical weight-and-balance and scheduling data to other operational tools. United stressed that the problem was not related to cybersecurity and that regional United Express flights continued to operate. The outage rippled through the network’s busiest hubs—Chicago O’Hare, Denver, Houston, Newark and San Francisco—causing widespread delays and cancellations. Flight-tracking firm FlightAware logged about 1,038 United delays, equal to roughly 35 percent of the day’s schedule, and more than 150 cancellations before the ground stop was lifted. The FAA said it offered support to clear the backlog, while Transportation Secretary Sean Duffy noted the disruption was confined to United’s systems and posed no broader risk to U.S. air-traffic control. United is treating the episode as a controllable delay and will cover hotel and other expenses for affected passengers. Although operations resumed overnight, the airline warned of residual delays as aircraft and crews are repositioned—a familiar recovery pattern following a similar technology failure at Alaska Airlines last month.