hello and i will try to clarify what i have experienced and been told by the gate personel when asking about being way down the list with lots of empty seats and not getting an upgrade. i am not savy as many on this board when it comes to terminology or even rules of many programs so maybe accidently saying some words wrong. also, my experience with delta is strictly domestic united states.
what i have seen, and been told by Delta employees at the gate is they look at who has paid the most for the economy ticket and from my understanding possibly cummulatively for the year. with Plat status on Delta i assumed it meant i was in front of gold etc. my status helps is true if tickets are equal, not true if i am on a lower cost economy fare from my experience. on the rare occasion i fly Delta (nothing wrong with the airline, they just are not my most flexible option most of the time) i buy some trips way ahead and get a relatively cheap fare price in economy and hoped to get the upgrade. someone who bought economy at a more recent and typically higher price (is this perhaps a y class ticket someone mentioned earlier??, here again not sure of my terminology) with a gold status will get the upgrade. i was kinda surprised and clarified with various people at Delta and with Centurion travel
also one other big surprise is that very few seats were "availble" or whatever they call it for upgrade even x many days out even with a lot of empty seats, because Delta staff told me they were saving them to sell at the gate. basically the upgrade price seems to be seen as extra revenue that would have been "wasted" on a free upgrade that someone with platinum status, as in my case, would have assumed would readily be available.
all the best
This is not correct. For domestic flights, with the exception of Y (full fare economy, which clears at time of ticketing), upgrades clear by medallion status and then fare class. What that means is that all upgrades are awarded first to diamonds, then plats, then gold and then silver. However, within an elite status tier, upgrades clear by fare class (i.e. an expensive B fare will clear before a cheap X fare). So if you are a plat, you should clear before any gold except golds on Y class tickets.
I won't deny that DL holds a lot of inventory for the gate to try to sell, but those seats should all be upgraded to if there are medallions on this list. The only thing to be aware of is that once you board the flight, you lose your chance to get an upgrade.