A fire alarm at United Airlines’ Network Operations Center near Chicago forced an about hour-long nationwide ground stop for all mainline flights Thursday evening, temporarily halting one of America’s largest carriers. The alarm sounded at United’s Arlington Heights facility around 6:30 p.m. CDT on July 24, 2025, triggering an evacuation of staff to a nearby backup facility. An FAA Air Traffic Control System Command Center advisory at approximately 23:26 UTC (6:26 p.m. CDT) recorded that United had ground-stopped its mainline fleet nationwide. “Employees have returned to our primary operations center, and the ground stop has been lifted,” United stated in … Continue reading Fire Alarm Grounds United’s Mainline Fleet for an Hour, Express Flights Continue