Unlike DL fares, I believe AF booking class will always be first letter of the 8-character fare basis code. This shows up on website when booking (see below). Not sure if fare basis code shows in app or email receipt. ITA Matrix will show booking class if you can price out your itin there. I have a receipt from a CDG-TXL itin in 2017 I booked on AF site and there's an Electronic_ticket.pdf file attached to email receipt with booking class in it. One direction booked in AF X class which earns nothing.