On MH (Malaysia Airlines), most Delta reps (for me happened three times in a row) seem to think that for Business award ticket the fare class is D (same as on MU and some other airlines, and DL itself). Wrong! It is actually I.

I had an mis-informed (clearly DL) agent put it as D and waitlist it. It took some 72 hours and still it was "waitlisted" and not coming back as confirmed. Each time I called to check, I was told that D is correct and that it will take "just a little longer" to get the response from MH.

Fourth time I called I got a well-informed pm-NW agent who immediately saw the fare class D was wrong, changed it to I, and it was confirmed by MH instantly and booked accordingly.