Whoa. AA interlines with TK?
I had no idea - I always assumed they only interlined with only OneWorld partners.
But because of you I discovered
http://www.aa.com/i18n/urls/partnerb...partnerbag#t-w
Wow, they interline with a ton of other carriers!
How does interlining work from a passenger perspective? Who do I talk to when I check in?
BA also has an interlining agreement with TK (and many other non-OneWorld/partner airlines), but their policy is that they will not interline unless it is on one ticket.
You will find that most airlines have interline agreements with most other airlines, that does not mean to say that they will interline baggage for separate tickets though.
You just need to inform AA at checkin, and have a copy of your e-ticket and itinerary for LHR-IST.