By Michael Conlon

CHICAGO (Reuters) - A storm that slugged parts of the central United States, dumping more than a foot of snow, mangled air travel from coast-to-coast on Tuesday as fierce winds carried bitter Arctic cold to the eastern two-thirds of the country.

O'Hare International Airport, all but shut down by blizzard-like conditions on Monday, may not return to normal operations until Wednesday, city aviation officials said.

United Airlines, the world's largest air carrier, canceled 175 flights there on Tuesday. Flights arriving at O'Hare from some destinations were delayed by as much as two hours because of blowing snow.

High winds on the East Coast were also blowing away airline schedules. Passengers from across the country headed to New York's LaGuardia were facing delays of up to seven hours, with flights into Newark International on hold for nearly that long. Travelers trying to fly into Boston faced four-hour delays, according to the Federal Aviation Administration's airport condition Web site.

Overnight, more than 80 percent of flights at Toronto's Pearson International Airport were canceled as the storm from the U.S. Midwest hit Canada's biggest city. And at Montreal's Dorval Airport, more than half of the flights were canceled to Toronto, Chicago and Detroit.

Nearly 15 inches of snow was recorded at Midway Airport in Chicago. Blizzard-like conditions forced police to close a section of Chicago's Lake Shore Drive on the city's Lake Michigan waterfront during the night.

Chicago commuters -- some of whom encountered several hours of delays because of ice-related rail line switching problems on Monday evening -- were sidelined again trying to get into work on Tuesday by equipment and other troubles triggered by minus 7 degree Fahrenheit cold.

In Minneapolis at midday on Tuesday, temperatures were minus 5 degrees Fahrenheit.

Schools were also closed across much of the upper Midwest for a second day.

Storm Takes Northeast Track

After causing mayhem in the Midwest, the storm took a northeasterly track, slamming into parts of western Pennsylvania and New York, where the city of Buffalo was again the target of winter's fury. Schools there were closed and some power outages were reported.

With the official start of winter still 10 days away, forecasters warned that the entire eastern two-thirds of the United States would feel the bite of the invading Arctic cold that triggered the storm, with the exception of the Florida peninsula.

Frigid temperatures were also reported as far west as Colorado. The temperature in Denver reached its lowest level in nearly two years on Monday night at minus 2 degrees Fahrenheit, according to the U.S. Weather Service there.

In Missoula, Montana, temperatures on Tuesday were 3 degrees above zero Fahrenheit.

Dallas-Fort Worth and much of north and central Texas were under a sleet and freezing rain warning. The mercury had already sunk well below freezing in West Texas and hit a low of 20 degrees Fahrenheit in Dallas overnight.

Dallas and other Texas cities were mobilizing sand and salt trucks.

The West Coast was spared the brunt of the cold snap. The Pacific Northwest was expected to have temperatures on the cool side, while inland the southwestern United States was expected to see temperatures as high as 60 degrees Fahrenheit.