Originally Posted by
MSPeconomist
O = BE award, so this is correct.
Z = deep discount BE fare class should also appear on the list, I believe.
Both S and X are coach fares on DL, although S is fairly expensive (just below Y B M).
Right, I forgot O is an award bucket. S used to be a discount BE fare... maybe X was a typo for Z? Didn't X used to be the upgrade bucket for flights sold as business (now OU)? Or was that V?