Carbon Fiber.

Without any hesitation, AA should replace the seat frames w/ Carbon Fiber. It's stronger than steel, lighter than aluminum.

more importantly, they should replace the largest wing panels on every plane w/ carbon fiber. Street racers have known this for years, replace your horribly heavy hood w/ a carbon fiber one and you will go faster because you are so much lighter. At a minimum, they could replace all of the access panels, that would have to save 100lbs on each aircraft. (Also, wouldn't consuming carbon as carbon fiber give them extra "carbon credits"?)

Also, I second the "remove a row of seats" and "charge extra for overwieghts" options. You have to pay for going over 50lbs w/ your checked luggage, already, this is the next logical step.... Stupid litigious society is never going to let that happen, though.

-SF