DFW Airport ranked No. 1 on FlightAware's MiseryMap on Wednesday afternoon with the most cancellations and delays in the U.S.

Just before 6 a.m., the Federal Aviation Administration had ordered all American Airlines flights grounded in the U.S. at the airline’s request.

The Federal Aviation Administration said American Airlines requested a ground stop for all of its flights for one hour early Tuesday, Dec. 24 due to a “vendor technological issue.” On top of that, thunderstorms are expected to roll in before noon. The Fort Worth area is already under a flash flood warning until 11:30 a.m.