Originally Posted by
Splendiz
Ok, I did actually book it. Couldn't reserve seats as I always got an error message saying something like I should check if the ticket is really valid. I had already the eTix so I asked Xiamen on Twitter to reserve the seats for me which they were able to do. Cannot reserve seats on KLM though because the KLM flights are issued in Y and they want to see money for standard seats.
Good catch with reaching out to Xiamen on Twitter. I flew them before though not longhaul, therefore seat didn't really matter in C (737 standard recliner). KLM codeshares however are a pain, you can't reserve seats in advance. You have to rely on OLCI 30 hours prior first departure. However, if your KLM legs are booked with KL flight #, you should be able to reserve seats IF you have a FB elite account and your FB # is attached to the booking.