Last week, I flew to/from Istanbul via FRA. I wanted to change (both going and coming back) on an AC flight to/from MUC. On the days I was interested in, there was (less than 1 week in advance of the departure) no I inventory in the MUC flights, but a fair amount of I inventory with the FRA flights. All of the FRA flights had C inventory, but many of the MUC flights had C=0 inventory. What is the reason for increased bookings in the business class of AC (and also LH?) flights between YYZ or YUL and MUC over FRA (of course, I do realize that there are more flights to/from FRA each day, compared to those to/from MUC).