Originally Posted by dkerr

This may be a point-of-sale issue. CX can restrict "sale" of fare buckets based on location of purchase. BA will use UK (LHR) as POS, AA is likely using USA (DFW?). So it could be that CX is controlling availability and making the seats only available for "purchase" in the UK.

I have found and verified this in the past... JAL Mileage Bank provides availability based on the location of your account... as I have both a US and UK address I was able to sign up for two JAL accounts and could compare availability when signed on with my UK account to that when signed on with my US account, and it can be different (this was several years ago, pre-COVID). ExpertFlyer also allows you to set point-of-sale location (but only for regular searches, not for award searches).

There have also been reports in the past that if you called AA reservations overseas, e.g. in Australia or UK, rather than regular USA number, they could find availability that US-based agents could not (time your call to regular working hours in the overseas country). But again, those reports are several years ago.