More than 1,300 flights were canceled Saturday and Sunday

O'Hare & Midway lead the list with the most cancellations & delays, according to FlightAware.com, an Internet-based website which tracks and monitors flight activity.

Accordingly, Southwest and United Airlines had the most delays & cancellations.

Wisconsin Air, a regional carrier for United Airlines, canceled the most flights by percentage out of any U.S. carrier on Sunday.