United Airlines resumes operations after brief nationwide mainline ground stop

1. United Airlines issued a nationwide ground stop due to a fire alarm. 2. Employees temporarily relocated to a backup facility but returned soon. 3. No flights were diverted, and United Express operations remained unaffected. 4. The incident resulted in a brief operational disruption, but operations resumed quickly. 5. United operates the largest U.S. airline fleet with 1,023 aircraft.