On DL0175 (A330-200) from AMS-ATL yesterday and was trying to improve my seat from 29J to an EC seat. 24hrs out I check my trusty DL app on my iPhone to see that 10C, 10G (both 1st EC seats after bulkhead) and 11G (great seat without anyone in front of you) are all available. I try to select one of these seats but the selection never takes so I call DL. The agent informed me that I was unable to change seats because KLM has control of it within a 48 hour window before departure.

When I arrived at AMS I proceeded directly to the KLM agent at the gate and made the same request. Was then told that those seats are no longer available. Thinking I missed out and they went to someone else, I pulled up the seat map on the DL app again to see those seats are still listed as available. I showed the agent my phone and she was shocked and called over all of the other agents. No one knew why it was showing that way.

Ended up taking a 150 Euro upgrade (after making a mad dash to the lounge to pay for it) and everything worked out quite ok. Just wondering if it was an unusual glitch or this is standard.