FlightAware.com said out of 1,223 canceled flights, 986 were within, into or out of the United States. The website said a total of 5,160 flights were delayed Saturday.
The St. Louis Dispatch said the St. Louis area got up to nearly 10 inches of snow and produced poor road conditions that left at least one person dead.
Whitney Gabathuler, 23, of Herman, Mo., was fatally injured Friday and Thomas Whited, 62, of New Haven, Mo., was seriously injured in a head-on crash on an icy bridge in Franklin County, the Missouri State Highway Patrol said.
Three people were seriously hurt in another head-on crash on a snow-slicked road in the county, police said.
Two women died in separate wrong-way accidents on Interstate 44 in St. Louis Friday and early Saturday morning, though it wasn't clear whether the crashes were weather-related. Becky Allmeroth of the state Transportation Department said the storm didn't help matters, but "we think their may have been other contributing circumstances."
Lake St. Louis, Mo., had received 9.7 inches, New Haven 8 and St. Peters, Mo., 7.6.
The snowstorm, which also buffeted the Chicago region overnight, was drawing a bead on the East Coast, forecasters said.
The storm chugged along the southern shore of the Great Lakes and was expected to impact more than 110 million people as it moved into the Northeastern United States, AccuWeather said.
Snow was expected to complicate a major Christmas shopping weekend in a wide swath from St. Louis to Boston and New York City. Air travel was also being impacted Saturday at major airports in Chicago and New York, the Federal Aviation Administration reported.
Transportation officials in New England had their snowplow drivers ready for the storm's arrival. "We are ramping up here," said Connecticut Transportation Department spokesman Kevin Nursick said.
About one-third of the state's fleet of 630 plows was already on the road before noon EST in anticipation of a long night of blowing snow and treacherous travel.
"We typically deploy geographically to meet the storm, so if the storm's rolling in east to west, we deploy east to west, so there's no wasted effort," Nursick told the Hartford (Conn.) Courant.
Chicagoland remain on alert Saturday for additional accumulations after a blustery Friday night. "Our Snow Operations Center is ready with the resources needed to stay on top of anticipated snowfall and windy conditions," Kristi Lafleur, executive director of the Illinois Tollway, told WMAQ-TV, Chicago. "Blowing snow may reduce visibility at times, so we are asking our customers to please slow down and drive defensively."