I know I've seen posts here from AMS regulars who have had success at getting UGs processed at AMS, but, on DL.com, it actually says this under Global UG Certificates:

10. Airport Standby: If an upgrade for the SkyMiles member and companion (if applicable) is not confirmed from the reservation waitlist at least three hours prior to departure, then the SkyMiles member and companion may request to be placed on the Airport Standby List, provided that request is made no less than 60 minutes prior to flight departure. Passengers on the Airport Standby List will be accommodated according to Delta's priority rules, which Delta reserves the right to change at any time. Airport standby is not available on Air France or KLM operated flights as well as Delta operated flights originating from AMS, BOM and CDG.

http://www.delta.com/content/www/en_...tificates.html