I always plan ahead but in this case I may be a little short of miles for an upgrade in advance. It's like this: I have a transpacific and transatlantic flight within 48 hours of each other and I'm trying to figure out how to maximize the upgrades. I can use miles to upgrade on the CO flight SPN-GUM-HNL-IAH-ORD. (At least I hope so - some threads make a note of the difficulty upgrading on this flight!) 48 hours later I fly NW ORD-DTW-AMS. But I won't have enough miles for a transatlantic upgrade until I complete the transpacific flight 48 hours prior. Hence the question about upgrading at the gate. Does NW charge a fee for this like AA does?

I've been spoiled living out here. 75% of my CO flights were elite upgraded (even for a NW silver) for SPN to Bali, Hong Kong, Japan, and Manila. Never had to use miles for an upgrade before!