Didn't BA and AA have to give up one of their slot pairs on the DFW rotation? I don't know if anyone ever actually picked up the slot (i recall reading something in the CMA review that they weren't actually sure if any competitors were interested in it, which raises questions on the judgment itself), but assuming they've still had to release it, moving to an A380 might have been sensible if they knew they could maintain market share on the route.