I bought the FCM "upgrade" DCA-CVG-SEA for $266.00 on 9/21/17. This turned out to be an exceptional operational performance by both GoJet and the Big D, as we got to CVG 20 minutes early and to SEA 30 minutes early.
On the way back, SEA-JFK-DCA, I got upgraded JFK-DCA about 4 days out; Delta offered me 5 hours up front in a flat bed seat (757) for $337.00. I passed. I was
#2 for 5 open seats 3 hours out; 60 minutes later, I was
#3 for 1 open seat, and an hour after that it was gone. Also, the flight went from 60 open seats in the back to 0.
Also, whenever I miss an upgrade like this, Delta always (and I mean always) puts a very large man in the middle seat.