A Spirit Airlines shutdown would ripple through commercial aviation, likely raising higher fares as the budget carrier exits the market, industry experts said.  "Any time you have a reduction in capacity and demand increases, airfares have nowhere to go but up. And that doesn't count the fares that are already rising because of the spike in fuel prices," CBS News travel editor Peter Greenberg told CBS News Boston. With a $500 million federal bailout stalling, Spirit plans to shut down as soon