North American airlines last month canceled more than 29,000 flights and delivered only 68 percent of scheduled services on time

as they were "hammered" by winter weather, FlightStats reported. Among the 10 largest U.S. airlines, AirTran Airways, United Airlines and American Airlines posted the best performance with more than 80 percent of flights on time, while JetBlue Airways and Southwest Airlines fell to the bottom of the pack, with 63 percent and 55 percent on-time performance, respectively.