United Airlines grounded all mainline flights across the U.S. on August 6, 2025, after its Unimatic system failed, snarling travel at major hubs. The tech glitch left passengers facing long waits and forced the airline to offer free rebookings through August 16, with the company stressing there was no cybersecurity breach.
United Airlines halted mainline flights nationwide after a tech system outage on Wednesday evening, leaving passengers stranded at hubs like O'Hare, Denver, and Newark. The issue, not related to a cyberattack, affected over 1,000 flights. Operations slowly resumed, but delays lingered into the night.