Last time I checked the 10% discount was only possible if all the sectors were operated by BA. I was refused it last month as I had 2 AA sectors (even though they were codeshare with BA flight numbers) booked on BA.com as part of a single PNR 6 sector booking. Come to think of it that doesn't sound right even as I write it.

(A bit more explanation in case you're wondering. I made a booking online in June for travel in July and forgot to put in the Chase discount code. I realised pretty much straight away and called BA. They said even if I'd remembered to put in the promo code it still wouldn't have worked as not all the sectors were operated by BA).