Originally Posted by
ISTFlyer
Yes, you could.
Even if you are connecting within separate tickets, TK also allows through checking baggage on separate tickets so you could also ask them to check through your baggage to Barcelona, at your first point of departure.
Thank you very much for your prompt reply. My first point of departure is a domestic airport in Denmark and the ticket is issued by KLM AAL-AMS-OTP-IST so a little doubtful groundstaff in AAL will be able to tag the bag all the way to BCN - but I’ll give it a try 😀