To add additional complexity, I was taking the LAX-BOS transcon in paid-First yesterday. The check-in agent said I had FL access. I got to the lounge and the desk said no. The reason? My paid First transcon was booked in A class because it was on a OneWorld Explorer ticket.

Of course I was able to whip out my Diamond card and get access on that (the flight was being credited elsewhere), but it was interesting to see that the letter from AA implicitly excluded one category of paid-F transcon.

Interestingly, although people here say the rules are being interpreted quite tightly, I never have any difficulty getting access to AC/FLs on my Diamond card when flying AA even with no adjacent international flights. I'm not sure if this is because I am on a OW Explorer ticket (albeit with stopovers in the US) or because it is just assumed that CX members are always on an international itinerary.