<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by SkyTeam777:
If so, what fare code must your ticket be booked in on a Delta-coded flight in order to upgrade using miles at the gate/counter.</font>
IIRC, same as if you were on a DL-operated flight - you must be ticketed on DL in Y/B/M.