Airlines have canceled more than 3,500 U.S. flights this weekend and delayed thousands more, citing weather in Florida and other issues. FlightAware, a website that tracks flights, noted major disruptions at several Florida airports, including in Miami, Ft. Lauderdale, Tampa and Orlando, as well as Baltimore, New York, and other airports around the country. JetBlue, Southwest, Alaska Airlines, Frontier, Spirit, and American Airlines were most affected, according to FlightAware, with JetBlue and Spirit canceling one-third of Sunday’s scheduled flights. Local news reported storms in Florida on Saturday. Several airlines said Sunday that operations are returning to normal. The spate of cancellations arrived as air travel is rebounding from the pandemic, with strong demand for spring-break flights. People on social media complained about waiting on hold or in lines for hours to get their canceled flights rescheduled and being stranded for days. “Severe weather in the Southeast and multiple air traffic …