Originally Posted by Keter

From what i see if i model on ITA its nowhere an UP fare, its a differential pricing:



This kind of pricing may lead to very interesting results if airline allow it without fully understanding this step. I recently got free J segments on SU (with just higher YQ paid compared to my premium eco fare) - but after this SU prohibited differential pricing for Y and W fares.

The sister AA J fare can also be used for differential pricing but I am not able to to get anything interesting. These construction rules are not even stated in international tariffs/ conditions of carriage. Somewhere else, very deep inside.

This is the reason also why only BA TATL is permitted for the discussed fare. Its a BA fare and TATL must be BA coded flight (the metal may be further restricted by fare rules), otherwise it will not price.