To make things even more complicated, I've learnt another new fact today.
Arrived into ZRH on LX in F together with a colleague, with another 2 colleagues on the same flight in C.
Apparently, F-customers can only take a guest into the lounge on departing flights, not on arriving flights. And as the 'regular' lounge in A is currently closed, we went to get a voucher at its front desk, which was handed to us by a lady who clearly would have liked to have spent her sunday elsewhere.
Interesting, LX, interesting.
