When American replaces its Super 80 fleet, which will have to happen eventually because AA won't allow its fleet to age as much as certain other airlines have, I think it will be with the 737-800. I think this for two reasons. First, they are only about 10 seats larger than the Super 80 (150 vs. 139 in the AA configuration), so it would not be a lot of extra capacity to add. Secondly, American took purchase rights for some 350-400 737-800's... obviously a move intended to be able to buy those to replace the MD-80's, as this is the only aircraft that tehy operate such a large fleet of. One last reason just came to mind... they are currently deciding whether to redo QQ's fleet to AA standards or to leave them as is. If they leave them as they are, they will be returning the planes as their leases expire and replacing them with, you guessed it, brand new 737-800's. It may take a while to replace to 260 Super 80's, but eventually it will happen, and I think the 738 will be the replacement.