I actually ran into this myself last month after forgetting to add my Miles & More number when booking a Lufthansa flight. I first tried updating it online under “Manage Booking,” but it didn’t sync properly. What ended up working was calling their support line at 877-764-3622—super quick. The agent added both my frequent flyer number and my KTN in a couple minutes, and I could see it updated in my reservation right away. I’ve also used the same number when I had to cancel a flight at the last minute, and it saved me a ton of stress compared to waiting on hold through the main airline channel. If you like step-by-step: log into your booking → check passenger details → try adding it there → if it doesn’t stick, just call that number. Honestly, calling was the fastest fix for me.
