It looks like I may have to go to Spain for a 3 day job, so looking at flight options I can see that both BA and AA have flights that will get me there reasonably (within guidelines of the corporate TA - meaning cheap of course!) It also looks like the AA flights are actually BA flights. So, does it make sense to book the BA flight and not the AA flights to ensure proper/most credit to my AS account? It looks to me that the SEA to LHR with the best connection times is the same flight but is operated by BA (and code shared with AA?) which would mean that it would not be credited to me if I booked it as an AA flight since it is operated by BA, do I understand that correctly?
Also, from what I understand
if I book the flights as normal paid tickets I cannot use my miles to upgrade after purchase?