i would tell them thanks on the 10k but no thanks, and file 261

it doesn’t matter where your ticket originated-261 applies to EU departures

any number of shenanigans could have happened - doesn’t really matter - this was a clear downgrade and you should be eligible for cash and your GUC returned. Assuming I’m reading the code correctly which is never a guarantee.

I’d encourage you to file for EC261 downgrade compensation, mostly because receiving the claim will force KLM to answer for what they have done in this situation.

In the future, I probably would have focused my attention on talking to the gate agents dispatching the flight rather than the lounge folks, and I would have been pretty quick to demand that a DL red coat (who does exist in AMS) get involved...

Since the OP purchased a economy ticket and used a GUC to get into another class -no money, good luck with the EU261.

2.If an operating air carrier places a passenger in a classlower than that for which the ticket was purchased, it shallwithin seven days, by the means provided for in Article 7(3),reimburse

sounds like some sort of shenanigans on the part of Klm. Most passengers wouldn’t know enough or be persistent enough to make an issue of it to the point of investigation so good job forcing the issue so that Delta can call out klm and hopefully it stops happening. On comp 10,000 miles is low.

I'd file for EC261 downgrade compensation if the ticket was reissued into D1. You had a business class ticket. However, a problem will be 75% of what to determine compensation. There's been a lot of discussion in the BA forum about EC261 downgrade compensation calculation when people have upgraded with instruments or used 2 for 1 certs as well as for tickets paid with points/miles.

My guess is that KLM was selling cheap upgrades at the airport on the day of departure, as they do in AMS. However, it could have been shenanigans too.

How close to departure were you upgraded? By this, I mean do you know when the upgrade cleared? It sounds like the ticket was reissued into D1 during your (first?) phone call to the DM line from AMS airport, which I guess would have been about three and a half hours before departure. IIRC there's language in the T&Cs for using GUCs exAMS, so I wonder whether it was really too close to departure and perhaps the DL DM agents should not have processed the upgrade.

It might have been useful to look at the seat map on EF. You might want to read the thread here about buying cheap upgrades at the airport from KLM for D1 flights exAMS to get a sense to the typical timing, as my impression is that while it's better to ask earlier of course, such cheap upgrades tend to still be available about two hours before departure (assuming it's not a day when D1 is fully booked by passengers with confirmed D1 tickets).

However, since zsmith2 (welcome back!) says that DL was right and KLM was wrong, I will 100% go with that opinion as a statement of fact and insist that DL pursue this as well as compensating you appropriately (and hopefully making KLM pay the cost).

BTW, DL has a "station chief" or some similar reasonably high level manager at KLM. The guy seems to be Dutch (and perfectly bilingual of course) but apparently works for DL rather than KLM. In similar situations, one could try to ask to speak to this person.

How do we handle this? I had a GUC applied weeks ago and I showed as waitlisted with the traditional twin itineraries listed in the app.

2-3 days out, there was still plenty of availability in J. Like J12 or something. I could still book tix in D1 at T-3 hours.

I asked KLM if I could pay cash or miles to UG at 9:30 AM for a 1:00 PM flight, but was told that D1 was now J0.

What’s a guy gotta do?

Something else that seems wrong here is that if we take the statement that D1 was oversold by one, there should have been some criterion used to select the downgrade victim. DL rules would seem to say look at status, then fare class, etc. I wonder whether KLM applied their own rules to this DL flight (or ignored any rules whatsoever and just put who they wanted into D1) and if so whether their rules say that the person without a seat assignment is the loser. I suspect this violates DOT rules which require USA carriers to have published rules for IDB and downgrade priority and to follow those rules. AFAIK having the flight ground handled by a partner or flying from a foreign location to the USA would not create an "anything goes" exception. As I see it, OP had a confirmed D1 reservation and a matching (reissued) ticket but flew in a lower cabin class than what had been purchased (in terms of money + GUC).

Look at the T&Cs for using GUCs on DL operated flights exAMS. The usual gate waitlist rules for using GUCs that clear at the gate for flights exUSA don't apply in this case. You were right to ask KLM about using miles and/or money (depending on your fare class), but I'm suspicious about there being no availability for someone asking four and a half hours before the flight as most people wouldn't have arrived at the airport so early.

It's too bad you didn't check J availability closer to departure, but how do you know it was J12? The most inventory that EF ever shows is 9 and counting empty seats on a seat map is meaningless. Note that fare class availability isn't additive, so seeing C9 and D3 doesn't imply J12.

To me, it looks like KLM decided to give the remaining D1 seats to their own nonrevs or friends and family.