I just read on another St Barts forum that WinAir has told US Air that all WinAir tickets must be issued either through WinAir or a travel agent. WinAir also has an agreement with US Air to check baggage through St Maarten to the U.S. destination. If you already have tickets for WinAir that you purchased through US Air, you might want to confirm your reservations.
www.caribbean-on-line.com/st-barts