First,
I think it is WAY too early to argue that AA can't successfully restructure, esp. in light of their financial performance for the quarter just announced. What is most important in those announcements is that they are growing revenue, something you cannot expect BK to fix. BK fixes costs and AA has enormous capacity to do that in BK. If AA can continue to build revenue - which it likely can do if it no longer has to keep capacity in the system which cannot produce good revenues, then it can build a profitable business plan.
Notably, the reason why US underperforms the rest of the industry is that they cut their presence in so many key markets so deep that they cannot now compete with the larger network carriers. AA mgmt surely realizes they still have access to alot of premium revenue and it is entirely possible for AA to compete with DL and UA even with a smaller size. AA's RASM growth was better than average of what is expected for the industry and undoubtedly superior to UA's. If UA stumbles for several months in revenue production as a result perhaps of the new res system (perhaps the revenue mgmt system is new too, I don't know), then AA has a very good chance of having a good foundation on which to restructure.
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As such I see no reason to believe that AA cannot successfully restructure.
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Discussions about what AA's future might look like if it can't restructure make little sense in light of the reality that it likely will successfully restructure.