Just managed to successfully upgrade AMS - IAD on KLM in November after having to HUCA twice after agents could not see availability in Z -- even though I could see Z3 on Expertflyer. I tried to get the third Diamond desk agent to transfer me to the JV desk, hoping for better results, but she told me the JV desk didn't exist. Like the previous two agents, she could not see any upgrade availability initally, but she put me on hold for 10 minutes to ask a colleague. When she came back on the phone, she told me that she had been able to find availability in Z, apparently by scrolling further down the screen. I'm not sure how to replicate this in the future, but I gathered that at the top of the agent's screen, it can appear that there is no GUC upgrade availability, but if they dig down, there is a second place where they can see inventory that might be reflected in Expertflyer but does not initially show up. Just a data point that may help.

Happy to get the upgrade but between this time and the last RUC I used in July, I've probably had to spend 2-3 hours on the phone each time to apply the certificate. Such a waste of time both for Delta and customers. I understand they are planning to allow certificates to be applied by pax on the website, but imagine that KL/AF will still need to be done manually...