I found a way to discover in which booking class the ticket will be booked BEFORE final booking.

Just try to book on the KLM BLUE BIZ sites and then look how many blue biz miles will be earned on the selected flights.

then look at the Blue Biz mileage tables and then you might figure out in which booking class it will be booked.


Though.....pffff what a waste of precious time to find it out in this way....
And they you also have to assume that the blue biz booking tool does not make a mistake !!!!!!!!!!!!!!!!