AA availability is generally the pits these days:

http://www.flyertalk.com/forum/ameri...iscussion.html

I find AS to be pretty good but as always it depends on what you're looking for and with whom. As I think you are aware you have to redeem for some partners online such as LATAM.

I'm confused by what you relayed from AS agents "it's available, but the booking class in economy has to MATCH the booking class available for that flight, so I can't get you there" - don't understand what that means or if you're referring to redemption on AS metal or partners. There is a flame-free Q&A thread at the top of the AS forum on here, you may want to start there.

There sometimes are issues with phantom availability on LATAM when I've looked at redeeming Avios for their flights, not sure but perhaps the same is the case through AA/AS. IME their award availability is poor on some routes in general.