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Ben Mutzabaugh, USA TODAY

A major winter storm is snarling flights in Chicago and elsewhere in the Midwest this morning, a disruption that comes at beginning of the busy Christmas travel rush.

Flights at Chicago O'Hare - the USA's second-busiest airport - are being delayed by an average of nearly two hours because of strong winds ahead of the storm, according to the Federal Aviation Administration's flight delay map.

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O'Hare is a major hub for both United and American, meaning this morning's disruption could ripple out and affect fliers at other airports.



Chicago's Midway Airport -- a major base for Southwest -- was suffering more sporadic delays and cancellations as of 8:10 a.m. ET.

The problems come ahead of a blizzard that's strengthening as it moves into the Midwest, and conditions are expected to deteriorate for air travelers today across much of the Midwest. That includes Chicago, where heavy rain is expected to switch to ice and snow sometime around 6 p.m. local time.

Already, the storm has snarled flights at several mid-sized Midwest airports. At Des Moines, for example,the airport's online flight information pageshows that all but two of this morning's departures there have been canceled. At Omaha, more than a dozen of the airport's morning departures had been canceled as of 7 a.m. local time,according to FlightStats.

A number of other airports - including those inCedar Rapids(Iowa),Green Bay(Wis.),Madison(Wis.) - have reported at least a handful of cancellations so far this morning.

Unfortunately for fliers, the storm is expected to bring worsening blizzard conditions much of the region today.

In one bright spot, flight schedules at Milwaukee's busy General Mitchell Airport have generally held up, though that could change as conditions worsen throughout the day.

The storm is even bringing problems to the South, where a long line of thunderstorms ahead of the storm could wreak havoc with flight paths in that region.

Hour-long delays at Memphis -- a hub for Delta -- had been reported earlier this morning by flight-tracking service FlightAware, though those problems appear to be easing.

But, in Atlanta, travelers flying through the world's busiest airport should pay attention to a line of thunderstorms that are expected to develop ahead of the winter storm as it moves East.

The greatest risk from those storms is expected to come early to mid-day Thursday. However, the delay threat depends on whether the storms develop into a north-south "line" long and solid enough to block flight paths west of Atlanta.

ORIGINAL STORY: Air travelers getting an early start on Christmas travel could run into turbulence thanks to a major winter storm that is expected to affect several of the USA's busiest air hubs during the next 72 hours.

The storm, strengthening as it begins to move east of the Rockies, has spawned blizzard warnings for at least a half-dozen states and is forecast to bring blustery weather to the Northeast by the weekend.

Most of the nation's big airlines responded to the storm's threat by Wednesday afternoon, enacting flexible rebooking policies for fliers scheduled to fly into the storm's path.

Earlier flight delays have subsided in Denver, where backups from the storm averaged about 70 minutes this afternoon, according tothe Federal Aviation Administration's airport delay map.

Now, as the storm pulls away from Denver, more severe flight disruptions are expected as the storm moves to the east.

Flights in smaller airports -- such as Omaha and Des Moines -- are suffering moderate disruptions this evening.

And, by Thursday, Chicago and its busy O'Hare and Midway airports are predicted to feel the storm's effects. Only a few inches of snow are forecast for the Chicago region, but the bigger concerns are the poor visibility and strong winds forecast to accompany the precipitation.

O'Hare is a major hub for both American and United while Midway is one of the top bases for Southwest. If the forecasts hold, both airports are at risk of having significant delays developing Thursday and lasting into Friday.

Already, flight-tracking companyFlightstats showed minor to moderate delays affecting flights at O'Hareas of 8 p.m. ET Wednesday. A few flights -- mostly to storm-hit airports in Iowa, Wisconsin and elsewhere in the Great Plains -- have been canceled.

Blizzard conditions also could snarl flights in Wisconsin on Thursday, possibly affecting Milwaukee, Madison and Green Bay.

Detroit, one of Delta's busiest hubs, is expected to see rainy, windy conditions starting Thursday, but the biggest threat to that airport comes Friday. That's when the precipitation is forecast to switch to snow, though accumulations are expected to be modest. Detroit's airport typically handles winter weather well, but travelers flying to, from or through the city should monitor conditions and check ahead on the status of their flights.

Similar advice applies to fliers passing through Cleveland, a busy hub for United, which faces a similar forecast for Friday.

With the edge of the storm forecast to move into the Northeast by Friday, the main concern for air travelers will turn to New York. Snow is not yet in the forecast there, but the predicted gusty winds, clouds and occasional rain are a bad mix for the metro area's delay-prone LaGuardia, JFK and Newark airports. Forecast winds also would bring the risk of sporadic delays at those airports on Saturday.

Even ahead of the storm's arrival,the FAA reportedNewark and JFK flights are being delayed by an average of up to 2 hours as of 8 p.m. ET because of strong winds. Winds also could disrupt flights Friday and Saturday in Philadelphia, though any problems that develop there are likely to be more sporadic.

And, in Atlanta, travelers flying through the world's busiest airport on Thursday should pay attention to a line of thunderstorms that are expected to develop ahead of the winter storm as it moves East.

The greatest risk from those storms is expected to come early to mid-day Thursday. However, the delay threat depends on whether the storms develop into a north-south "line" long and solid enough to block flight paths west of Atlanta.

As always, customers flying over the busy Christmas holiday travel period should check ahead on the status of their flight, and keep in mind that fair skies at their destination don't mean that they're immune from weather delays. For example, a flight from St. Louis to Houston could become delayed or canceled if the aircraft or crews scheduled to operate the flight gets stuck in snowy Wisconsin.