A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
I assume you don't have status on AA.
What do you see as fare class and booking class on the ticket, segment by asegment? My guess is that if space in FC opens (or opens in the fare class that you purchased, more precisely), it would be a matter of contacting BA and asking them to change the ticket, assuming that it's BA ticket stock and purchased directly from BA.
You might get more expertise if you ask in the BA forum, so I think you should ask a mod to move this thread there.