I have a similar question or actually 2 questions:
1. I am considering doing BKK-HEL-TLL // TLL-HEL-LHR but I don't know if it will be possible to turn around on the same plane in TLL with checked luggage.
I wonder if AY can just check my luggage for BKK-HEL-LHR... I will fly the full tickets to TLL and back (otherwise the HEL-LHR would get cancelled), but it would be easier without luggage.
2. This would be the return portion of the trip. On the outbound, I will take the ferry to TLL and then fly TLL-HEL-BKK. I wonder if AY can check my luggage in HEL, before I have actually gone to TLL and flown back?
1/ I you don't take same plane turnaround, totally possible to do. I'd build my itinerary on the presumption that AY WON'T check BKK-HEL-LHR and therefore taking one later TLL-HEL and accordingly the HEL-LHR
2/ I have a gut feeling that it won't happen, but no harm in trying. Would be interesting in hearing back, how you fared.