Well, my dad is ticketed to go TPA-STL-IAD-LHR-SOF in November on a 40k BA off-peak award.

AA cancelled many of the STL flights, and as a result he has been switched to later flights on TPA-STL (AA), STL-IAD (AA) and IAD-LHR (BA). Problem is, the IAD-LHR flight lands in London at 10:00, while the SOF flight leaves at 08:40

Whom should I contact to fix this - BA or AA? He has a couple of options, the best being TPA-ORD (AA) ORD-LHR (BA) and then connecting to the SOF flight. The BA flight has award seats avail, but the TPA-ORD does not (it is wide open but no 'T' class). Should I press BA or AA to put him on that itinerary, given that the schedule changes were AA's fault?

Thanks for the advice!