I've had the unhappy experience of trying to move my mile balance with NWA WorldPerks to KLM Flying Blue. This was a required process after I moved from the United States to Europe. In a nut-shell, my miles were transferred out from WorldPerks, but never arrived into the Flying Blue account. All my efforts to contact Flying Blue led to no result, none of my letters were ever answered. This is a hell of a way to treat a platinum customer. It has been a month now since I "transferred" miles to my KLM account, and there is no end in sight to this saga.