Flights that were already airborne at the time of the halt were not diverted but were warned of potential delays and told to prepare for “airborne holding due to excessive demand.”
A spokesperson for United confirmed that the fire alarm led employees to shift to a nearby backup facility as a precaution.
“A fire alarm sounded at our operations center, which caused employees to move to our nearby backup facility and resulted in a brief nationwide ground stop of United aircraft,” the airline said in a statement.
“No flights were diverted, and United Express regional flights were not affected.”
While the emergency stop was short-lived, the scale of the impact was enormous. United Airlines operates the world’s largest fleet, with over 1,000 aircraft—each one briefly held from departure until operations resumed.
Tensions Rise Amid Growing FAA Challenges
The United halt came on the heels of Alaska Airlines’ own travel chaos just five days earlier. That incident involved a system-wide IT failure that prompted Alaska to request the Federal Aviation Administration (FAA) halt all mainline and Horizon Air flights. Planes were grounded for several hours, starting at approximately 8 p.m. Pacific Time and only resumed around 11 p.m.
The dual incidents highlight ongoing vulnerabilities in U.S. aviation infrastructure, which is already under strain amid deep staffing cuts at the FAA. President Trump’s ongoing initiative to streamline the federal workforce reportedly led to the dismissal of as many as 400 FAA employees in recent months.
Fallout from the Alaska Airlines Ground Stop
Alaska Airlines, which operates a fleet of 238 Boeing aircraft and maintains major hubs in Seattle, Portland, Los Angeles, and San Francisco, was forced to extend the ground stop to its regional subsidiary, Horizon Air, which operates 45 additional aircraft.
“At approximately 8 p.m. Pacific on Sunday, Alaska Airlines experienced an IT outage that’s impacting our operations,” the company said.
“We requested a temporary, system-wide ground stop for Alaska and Horizon Air flights until the issue is resolved.”
Although flights resumed that night, the airline warned of “residual impacts” that would ripple across the schedule into the following day.
Passengers across the country shared stories of long waits, frustration, and a complete lack of information.
One Alaska Airlines passenger revealed he and his fiancé were stuck on the tarmac in Denver for two hours before the crew instructed everyone to disembark without any clear update. Another traveler, Riley Davis, recounted being stuck for two and a half hours without food or knowledge of when the plane would be assigned a gate.
“Since they can’t coordinate exact gates, they are manually assigning gates via radio communication,” Davis wrote on social media.
“I would love to know when I can get some dinner—I’m starving.”
Social media lit up with reports of Alaska Airlines jets stranded across the country, parked on tarmacs with nowhere to go.
Looking Ahead
With back-to-back national ground stops from two major carriers in less than a week, passenger confidence is being tested, and pressure is mounting on both airlines and the FAA to ensure systems and contingency protocols are more resilient.
For now, United’s brief operational disruption has been resolved, and no major delays were reported beyond the initial pause—but the fire alarm incident has underscored just how fragile air travel systems can be in moments of crisis.