Question about Flex tickets. I have a round-trip booking XXX-HEL-XXX, where XXX is an airport in Finland. I wanted to add another leg so the flights would be XXX-HEL-YYY YYY-HEL-XXX, with YYY being outside of Finland. I was told this is not possible since the ticket was originally booked as a domestic ticket. This sounds strange, but is it correct?