Last updated: 11:50 ET. Next update: at 4 pm AND.

Airlines passengers have been facing delays and cancellations Sunday in the Midwest, one of the busiest travel days of the year, as crowds of vacationers return home after Thanksgiving.

At the national level, nearly 500 flights were canceled and 700 more delayed at 11:50 am ET, according to the FlightAware Flight Tracker.

Most of them arrived in the Midwest, where a winter storm brought snow, ice and rain over parts of the Great Plains and the Midwest. Blizzard conditions were possible Sunday in parts of Iowa, Illinois, Missouri and Wisconsin.

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Weather conditions resulted in flight cancellations at several airports in the region, including Kansas City, Missouri; Omaha, Nebraska; and Des Moines and Cedar Rapids, Iowa.

But the biggest impact on air travelers was Chicago, where more than 200 combined arrivals and departures were canceled at 11:50 am ET in the busy O'Hare airport.

O'Hare is a major hub for United and the United States, and many cancellations were made by affiliated airlines providing regional flights under the United and American brands. By the FlightAware account. cancellations accounted for more than 7% of the full Sunday schedule at O ​​& # 39; Hare. About 100 O'Hare cancellations were made as a precaution on Saturday night as the storm forecast stabilized.

Cancellations were also held Sunday morning crossing the city at Chicago Midway Airport, the major base of Southwest Airlines. 122 combined arrivals and departures – approximately 15% of the time of day – were canceled at 11:50 am ET.

Many major airlines have removed the change fees.

The details vary from one carrier to the other, but – in general – waivers allow affected customers to make a change to their itinerary without paying any up-to-date fees up to $ 200.

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