With a major winter storm headed toward the Hudson Valley, travelers are bracing for big headaches this holiday weekend.

The huge storm stretches all across the country, from the Plains and Midwest to the East Coast, and that spells big troubles for travelers - not only in the air but also the roads and rails.

Right now, 215 million people are under some type of winter weather advisory.

Southwest Airlines said it has canceled 500 of its 4,000 scheduled flights on Thursday and Friday. Airlines started canceling flights in and out of Denver Wednesday, with more today.

Hundreds of flights expected to be canceled today at O'Hare and Midway airports in Chicago

Delta, American, United, Frontier, Alaska, Southwest and other airlines have been waiving change fees, and offering travelers the option of choosing new flights to avoid the bad weather.

Bus and train travelers were also bracing for cancellations and delays. As of late Wednesday, Amtrak had canceled train service on around 30 routes, some through Dec. 25. Greyhound canceled bus service on 25 routes for Wednesday and Thursday.

All of the early morning flights out of Westchester were on time, and the biggest worry for these travelers was the long lines. Airport officials say if you are flying for the holidays, you have got to get to the airport at least two hours early, otherwise you risk big problems. Officials are also urging travelers to call their airlines to check on cancellations.