D can be very short on the popular business flights. For example, on QF52 SIN-BNE last Friday (which Ihad been watching for several weeks), the load was showing J9 D0 I0 U0 for about 3 weeks. In fact, at one point I was waitlisted for D, but eventually ended up buying K. In the last week before the flight, J steadily dropped to 0. This may have been due to waitlisted D's being cleared, of just more J sales.

Every other day of the week had D availability closely matching J. Just Firday showed D0.