Originally Posted by
Dover2Golf
I think the account has to be open before the flight, opening it afterwards does not work IME.
It used to work retrospectively, I did so back in 2014 when I opened my M&M account after actually having flown two LH legs.
anyway, might have changed since then and the language on the website can be read as in different ways:
Originally Posted by Miles-and-more.com
Mileage credits up to six months retrospectively.
Even if you were not yet a member at the time of purchase or booking
could mean retrospective credit works if you signed up after the flights or only if you’d honed up between the booking and before the first flight. But the later doesn’t make much sense... because then you could also just add the FFP# at time of check-in