The policy change comes just months after Southwest tightened the policy for plus-sized passengers who may require an extra seat. WASHINGTON — Southwest Airlines has updated its policy for plus-sized travelers to allow for gate agents to give customers extra seats free of charge if needed. “On flights where adjacent seats are available, our Agents at the airport are empowered to provide an additional seat at no extra cost to Customers who require one,” an airline spokesperson confirmed on Friday. “If another seat is not available, we will work to accommodate the Customer on a later flight. We continue to…