A United Airlines outage has prompted a ground stop across the country, including at major airport hubs in Newark, Chicago, San Francisco and Houston.
The airline said in a statement it was facing a "technology issue," causing mainline flights to be held at their origin airports. It does not affect United's regional flights.
Flights that are already in the air will be allowed to continue to their destinations.
"We expect additional flight delays this evening as we work through this issue," United said. "Safety is our top priority, and we'll work with our customers to get them to their destinations."
Further details about the problem and what caused it were not available. It was not clear how quickly the ground stop would last, but ground stops can last anywhere from a few minutes to a few hours.
Responding to frustrated flyers who reached out on social media, United said it was aware of the system issue and was working to resolve it as soon as possible.
United had the most delays of any domestic airline Wednesday, according to tracking statistics from FlightAware.com. It was not clear if the number of delays listed included the ground stop flights.
