Originally Posted by
MSPeconomist
AFAIK additional APD isn't owed for OPUPs (nor for nonrevs given premium cabin seats). If people use instruments to "upgrade" in advance to C+, I would expect DL to charge APD, just like they do for upgrades into D1, with payment required before the ticket can be reissued (and also for the French luxury tax on upgrades into D1 exCDG). However, for upgrades at the gate, I'm not sure that GAs have the time to charge credit cards.
I thought it was still owed, but for OPUPs DL paid it and nonrevs had to pay it to fly in D1. Of course the rules have changed over the years, so no way tp be certain.