Whew! Southwest Airlines is shaking things up, and some travelers are not here for it. The airline long praised for its approach to plus-size passengers, is officially ending its "Customer of Size" policy. Starting next month, passengers who need extra space will now have to pay upfront for additional seats, a change that could make flying more expensive and leave many questioning the airline's once "customer-first" reputation.RELATED: No Fly Zone? Flight Cancellations & Delays Worsen Amid Longest Government Shutdown In U.S.