I often make bookings on AA domestic flights with avios and usually use the AA website to check availability before ultimately booking on ba.com For a trip next weekend, the AA website (along with KVS and EF) was showing 0 availability in T class on my preferred dates but had seats in U. I went to ba.com to book the flight in U class but was shown availability in T class too! I clicked through and it ticketed so it wasn't a website error.

Not sure why this happened but am not questioning it. ^