Originally Posted by
jackr27
and the third time (speaking to the Spanish line) I was told that an upgrade isn't possible as business is full (it isn't).
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this may very well be possible. Business Class have around 5-6 RBD (revenue booking designators). „I“ is for upgrades within the LH group. That may be closed, but others (P, Z, C, D, J) may be open for sale.
Also, even if „I“ is open, you may not be able to upgrade, but booking full award may be (based on own experience and confirmed by LX)