Southwest Airlines, the largest carrier at BWI Marshall Airport, is ending its popular free checked bag policy for flights booked on or after May 28. The airline, which controls 70 percent of the market and passenger share at BWI, will soon require most passengers to pay for checked luggage – a significant shift from its long-standing "bags fly free" policy that set it apart from competitors. "Instead of two bags fly free, it's now two bags fly for a fee, and we're still unclear as to how much these bags are going to cost," said Katy Nastro, a travel expert and spokesperson for the Going Travel app. See more: www.wmar2news.com/matterformallory/southwests-free…