United Airlines ground stop has been lifted after IT problems

HOUSTON (KTRK) -- United Airlines' confirms that all domestic flights that were grounded Sunday have been told to proceed.

Earlier Sunday evening, flights were grounded due to IT issues.

"We have issued a ground stop for all domestic mainline flights due to an IT issue. We are working as quickly as possible to resolve this issue and get out customers to their final destinations. We apologize for the inconvenience to our customers."

ABC13's Tim Heller was on a plane in Chicago experiencing delays and tweeted from a United plane.

Heller reported at 7pm that his pilot announced it would be at least another hour.