Another intense winter storm system stretching from the upper Midwest to the Northeast will once again test US airlines during the busy holiday travel period.Service is still trying to recover from days of disruption that led to more than 3,600 cancelled flights between Dec. 26 and Dec. 28. Another 30,000 flights failed to depart or arrive on schedule over that timeframe, FlightAware data shows. As of 10:00 a.m. New York time Monday, more than 500 US flights on Monday are canceled and another 2,000-plus are ...