Hope this helps
D CLASS= FULL PAYING TICKET WITH 1 YRS VALIDITY TO TRAVEL(THIS IS THE COMMERICAL CLASS BUT IT IS ALLOWED TO USE FOR REDEMPTION BUT U CANNOT EARN MILES)
SAME AS Y CLASS WHICH IS THE FULL ECON CLASS COMPARED TO THE ECON SAVER WHICH IS THE X CLASS
THESE COSTS 50% MORE THAN THE ECON SAVER ANS BUSINESS SAVER TKTS