The snow/ice event that hit the northeast this weekend played havoc with airline flight schedules around the country. USAirways appears to have been hit hardest. They were late to cancel flights in advance of the storm and as a result appear to be having more difficulty recovering than other airlines. Lingering issues with a reservations system cutover 2 weeks ago have likely impacted their ability to reacommodate passengers as well.

Here are some links to news articles on the subject:

Washington Post

New York Times