If you booked the BA flight with AA (which happens on award or TATL flights even when trying to avoid YQ) you will want to try and select your seats on the BA flight segments but most of the time the AA website won’t let you do that part. Some times on codeshares, Operated by British Airways, all you need to do is add your British Airways Executive Club number to the booking. After a few minutes, log into your BAEC account, and look at your upcoming bookings. You’ll find in there your BA booking reference for the BA legs, and will be able to select your seat, see avios to be earned etc.
if you booked the BA flight under the BA flight number, eg British Airways flight BA 345, then for some reason your BAEC details won’t get passed over. What you need to do is, bizarrely, go to the Qantas “Manage My Booking” page, and enter your American Airlines reference. Scroll down to the Seats section of the page, and you’ll see something like:
Seat selection is only available for flights operated by Qantas. To select seats and manage your booking, visit British Airways site with your booking reference #12ABCD
Then take that booking reference shown there, go to the BA website, use that with Manage My Booking, then enter your BAEC details + pick seats + see avios details + etc
The advantage (pardon the pun) is that you don’t have to call AA to get your BA record locator. Normally this isn’t a big deal. I researched this because I’ve tried to set aside time to call AA for the last couple weeks only to find myself ready to call on a bad IROPs days or Christmas eve which didn’t seem like a good idea.
Here are a few screen shots.
Enter your AA record locator and last name
Then scroll down to seat selection and you should see the above. I wouldn’t worry about the AA flights that show “Not Selected” if you know you did this with AA already. Your just accessing this page to get the “booking reference”# shown above so you can go plug that into the BA website.