(MEREDITH/CNN) United Airlines has lifted its ground stop after a computer glitch halted airlines for more than two hours Sunday.
United Airlines tweeted: "The ground stop has been lifted. We’re working to get flights on their way. We apologize for the inconvenience to our customers."
International flights were not affected. U.S. officials say the ACARS (Aircraft Communications Addressing and Reporting System) was buffering due to low bandwidth - which led to the groundings.
Chicago-based United Airlines and United Express operate more than 4,500 flights a day to 339 airports across five continents.
Other computer glitches have hit airlines.
In October, United flights were delayed for hours because of a computer problem, causing a social media firestorm.
United said it experienced an issue with its weight reporting system that was later resolved.
In September, British Airways suffered a computer problem that caused delays and long lines at airports in the United States and Europe.
In August, Delta was forced to cancel around 2,000 flights after a major system failure. That came only a few weeks after an outage caused more than 1,000 cancellations at Southwest Airlines.
UPDATE: The ground stop has been lifted. We’re working to get flights on their way. We apologize for the inconvenience to our customers.— United (@united) January 23, 2017