Originally Posted by kuroko

I guess first saver is a companion A class fare or a special promo fare in A. The normal A class fare should always be a flex.

However it looks for me like a little mess. Before it was pretty clear I and higher was flex (i.e. for Business). Now sometimes I is a saver or a flex, C is sometimes a flex or a flex plus, depends always from the o/d (and those are not booking classes for promotional fares. I can understand that a O class is sometimes a special/saver fare as they are diff promos running under O class).
The only indicator is the farebase for the level and no longer the booking class.