Yes, there are time when the flights are just plain full. Last summer I was flying DTW-LAX as part of an East Coast to HNL itinerary flying on a full Y itinerary using the SWU, Million Miler, Delta Reserve Card. The dXXX corporate travel agent would not issue the ticket until a day before the travel. The DTW flight was a prime time for morning arrivals from Europe in business class to connect to the West Coast. I never did make the upgrade despite the DM status, the Y fare and cashing in an SWU for the itinerary because the ticket was issued after all the other medallions had upgraded. I guess that's why the flight attendant from first class came to me a couple times in economy class and kindly asked if I wanted anything.