With ice on the runways in Dallas and a blizzard expected in Chicago, U.S. airlines are canceling thousands of flights and erasing much of their service in the middle of the country.

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Flight tracking service FlightAware has logged almost 6,000 cancellations for the day. More are expected on Wednesday.

Ice shut down Dallas-Fort Worth International Airport for two hours on Tuesday morning. One runway later re-opened. But American Airlines spokesman Tim Smith says the airline is hardly operating at Dallas because high winds make it unsafe for de-icing employees to work in the bucket trucks.

Chicago O'Hare was seeing delays of more than two hours. A United Airlines spokeswoman says about 300 departures will be canceled in Chicago starting in the afternoon, when the snow is expected to pick up.