Dallas Hail, Tornado Threats Are Grounding Hundreds of Flights

A powerful band of thunderstorms threatening softball-sized hail, tornadoes and dangerous winds are menacing Dallas and the US South, grounding hundreds of flights and knocking out power to thousands.

As of 3:45 p.m. local time, 278 flights were canceled at Dallas Fort Worth International Airport with dozens of others grounded in Chicago and Atlanta as the storms send ripples through US air traffic, according to FlightAware, an airline tracking service.