I was just thinking about something. The Consortium is planning on putting a carbon fibre wing on the 3XX from what I understand. That's pretty dang cool! Its really light, and *very* strong. That would mean serious operating cost reduction. But, I've realized a major drawback while reading another discussion. What happens if it gets a ding?
Singapore Airlines bought 320s. They were doing great until a maintenance mishap caused the fin (which is composite) to be damaged slightly. If it had been an aluminum fin, it could have been repaired for a couple thousand dollars. Instead, it required a whole new fin with a 6 figure cost. That wiped out the fuel savings for the life of the jet.
Imagine a similar ding on a 3XX wing. It would be even more expensive because it would need replacement. That could be the end of that plane!