United Airlines grounds all U.S. flights because of a computer problem

United Airlines said all of its domestic flights were grounded Sunday because of a computer problem. Company spokeswoman Maddie King said in a brief statement that it issued a ground stop in the U.S. because of an "IT issue." The company did not provide any more details, and it was not immediately clear how many flights were affected. Chicago-based United Airlines and United Express operate more than 4,500 flights a day to 339 airports across five continents.