I know that you'll all know but I'm unsure. I have a series of flights with AA which were booked throught BA.com. I have a confirmation from BA and a locator. If ever I want to check or change the seats it takes me to AA.com where the entire booking exists but with another locator of course. My BA Exec card is in the booking.

My question is this - with which airline do I check in? Will it allow me to check in Online with the BA flight code? If it does not allow me to do this - do I go to BA or AA. AA will of course have their security people vetting you before you check in and it would amaze me if I were to be put throught the same procedure. Do I then go directly to AA? This I should add is MAN -ORD.

So if this is a daft question, and it has probably been aired here 673 times, but it passed me by. Any help gratefully received.