Millions of travelers were affected on Monday as widespread storms continue to sweep through the country following the Thanksgiving holiday weekend, disrupting one of the busiest travel days of the year and causing chaos on roads and runways.

As of Monday morning, CNBC reported that 172 flights were canceled and 450 were delayed. That follows more than 950 flight cancellations and about 8,400 delayed flights on Sunday.

The wintry conditions got so dangerous, they caused several accidents, including a plane that slipped off the runway at Buffalo Niagara International Airport on Sunday, CNN reported. On Saturday, nine people were killed in a plane crash in blizzard-like conditions in Chamberlain, South Dakota.

And on the roads, a 25-vehicle pile up in Garrett County, Maryland, snarled traffic, CNN reported, with state police saying heavy fog had created limited visibility there.

Heading into the week, more disruptions are possible as snow continues to sweep across the East Coast. More than a foot of snow had already fallen in Albany, New York, on Monday with cities like Boston, New York City and Philadelphia under a winter weather advisory, according to The Weather Channel.

Planes in snow
Credit: Stephen Maturen/Getty Images

"We're seeing values upwards of 8 to 12 inches and even along the Catskills and higher terrain, we're seeing values upwards of towards 15 inches in that area," Lara Pagano, a meteorologist for the National Weather Service, told NPR about snowfall in New York and Maine.

The havoc comes as a record 31.6 million travelers had been predicted to fly during the Thanksgiving holiday period, according to CNN.

Several airlines moved to mitigate cancellations and delays, easing the way for customers to change their flights. According to CNBC, American Airlines waived change-fees for travelers flying Monday and Tuesday to or from more than a dozen Northeast airports with Delta, JetBlue and United offering similar waivers.