A couple of years ago I was just short of making platinum. After reviewing my account I discovered enough missed segments/miles to make the difference up. I first called and then emailed them the info. They credited my account right away and I made my Platinum status again. Ever since then I'm anal about checking my account. Every time I do a flight itinerary I check my account online to be sure everything is credited. Usually NW credits within a couple of days of the flight. On codeshares or other airlines sometimes it takes a couple of weeks. Another thing I've learned is that if your original itinerary is changed by them and results in less credited segments/miles then if you call and show them, they will give give you what you would have been credited on the original itinerary. If you're like me and are always sweating making Platinum, then ever mile adds up!

Tracy