And B6 isn't a serious threat to AA at BOS?
Both AA and DL used to have this route. AA used to have a mini-hub at BOS. Heck TW used to have a mini-hub at BOS before AA.
AA operations at BOS were a mess for most of July because of East Cost weather. I don't think I have had one round trip on AA this year where every flight was close to on-time. I'd be happy with 15 minutes late and OK with 30 minutes late. But, every round trip I've had on AA this year has had at least one flight over an hour late. AA needs to fix things. I'm not sure that adding another flight that is going to be late is what AA should be doing.
B6 is not a threat to AA at BOS. AA does not care about BOS like US Airways did. AA has JFK, LGA, DCA, and PHL in the Northeast. BOS is not a priority. Honestly, I would not be surprised if AA dropped BOS-BUF/PIT where they have competition with B6, and seasonal BOS-CDG service with weaker European demand and DL/AF competition (maybe they shift it to LHR because of the BA JV).