A winter storm hitting the mid-Atlantic combined with the pandemic to further frustrate air travelers whose return flights home from the holidays were canceled or delayed in the first few days of the new year. According to tracking service FlightAware more than 3,000 U.S. flights and more than 4,800 worldwide were grounded as of Monday evening. Another 13,000 flights were delayed, including 6,000 in the U.S. That follows Sunday’s cancellations of more than 2,700 U.S. flights, and more than 4,400 worldwide. Travelers could take hope from an improving weather forecast. Airlines had canceled fewer than 400 U.S. flights scheduled for Tuesday.