Luggage weight and fuel saving

I mostly fly American Airlines, which is famous for its finding ways to save on fuel costs. From not painting the planes to removing the olives, they will do anything to save fuel. However, the ways to reduce fuel costs are getting fewer and further between. There one seemingly obvious way that they have over looked. Reducing the weight of the bags people bring on. Sure some people pack by weight, but most bring what they need regardless. So the less the bag weighs the less fuel it takes to transport it.Besides working with luggage companies to reduce the weight of the bags, airlines should consider rewarding people for packing well under-weight. Either with coupons for airline related goods and services or extra frequent flier miles. Positive reinforcement works better in cases like this, since it encourages good behavior and doesn't lead to bad press that results from additional fees. They should also consider luggage trade in programs. By watching for and replacing bags that are very heavy by themselves the fuel savings could be significant. (By working with companies that make carbon fiber products it could be possible to use the scraps to make bags with less metal without reducing strength.Plus the cool factor, your bag was once part of an Indy car or a Dreamliner.) This program would be costly but the fuel savings would be significant. By standardizing the bags the loading of the bags could be greatly simplified. (They would create a thriving after market in bag customization, with "skins" being a way to ensure "many bags do not look alike".) Even with all the savings the airlines would never do something like this on their own. I suggest the government offer them carbon credits or tax incentives, to get them to help themselves.The other thing airlines could do is encourage people to lose weight, but I think helping peoples bags slim down is the more practical option.