You have to look at the aa operated flight which is at about 840 pm, in the end what you want to do is going to be very tough this far out, the flight from Bos to Lhr is only 545 minutes or so not the end of the world if the upgrade doesn’t clear, but finding inventory for a heavy travel month like sep is going to be tough going yet your chances of clearing are decent but you won’t know until much closer to the flight,