A massive winter storm sweeping across the US triggered what is shaping up to be one of the worst air travel meltdowns since the Covid-19 pandemic, forcing some major airlines to cancel more than half of their scheduled flights. More than 16,000 US flights have been canceled from Saturday through Monday, according to data from flight-tracking website FlightAware, as the storm pushed into major population centers and snarled airline networks nationwide. Airlines scrapped more than 10,300 US flights on Sunday alone, according to FlightAware.  Bloomberg's Julie Fine joins Bloomberg Intelligence to report.