Chicago-based United Airlines suffered another huge computer outage that delayed passengers around the globe for hours.
The outage at the world's largest carrier lasted for about two hours this morning. United tweeted just before 10 a.m. that the system was "back up" and running and operations had resumed for affected flights.
It affected half of all flights on United's main network and was at least the third major outage for the airline since June. Few effects were felt at O'Hare International Airport and no departure delays were noted.
As of 11 a.m. ET, there were ten departing flights delayed “of the 30-minute variety” at San Francisco International Airport, spokesman Doug Yakel told NBC Bay Area.
Passengers said they were being told by pilots and airport agents that computers were down and they didn't know when the system would come back. Some fliers had been waiting nearly 2 hours to depart.
Major delays across the world can easily ripple throughout an airline's network. United runs about 5,500 flights a day worldwide.
A spokesman for United Continental Holdings says the outage didn't affect its regional flights on United Express. Spokesman Rahsaan Johnson says only those airplanes that came from the former United were affected.
United has been struggling with technology problems since March, when it switched to a passenger information computer system that was previously used by Continental. The airlines merged in 2010.