I have been platinum for several years and always had great difficulty getting any upgrades on international flights. On my next trip, I am settling for one on the way back from AMS to MSP on a DC 10, then reversing directions to get home to CMH! No upgrade (yet) on the way over - but I will keep calling. It is hard to imagine it being worse for Silver and Gold. This is a (very) weak link in the NW "brand loyalty" program compared to other airlines, in my opinion.