I would just be careful -- it seems to me as if AA may actually be selling a lot of F fares on this route these days (the horror!). Either that, or there are enough people on the waitlist for J-F upgrades that I don't even see the interim step of "A" availability and F ticks down and down as the flight approaches. I had been keeping tabs on this route for a colleague last week. Friday afternoon and evening flights back seem particularly hard, in both F and J (paid!). But if you can be flexible, you should be able to find A on one or two of the flights at least, a few days in advance.