Originally Posted by
r2d2
But the official rule for check-through on separate tickets is that both flights need to be Finnair-operated and on Finnair ticket stock, so a ticket booked on the BA website doesn't qualify. Be prepared for a no.
I asked about this a while ago and the plat customer service said "it also depends on the first airport" without being able to clarify why or how or which airports can or cannot do it.