I got called in to do an out 'n back to Syracuse AKA Sarasota, the flight downsized to a 50 seat. As the Capt and I sit there in the plane they changed our planes destination to Palm Beach. We were all ready to go to Sarasota and had the plane preflighted and warmed up when they sent down ready reserves to do the flight to PBI. I guess I'm just not seeing the big picture.