DElta tweet regarding GUC availability
 

Me: Could you Check if GUC space opened on DL 89


Delta Tweet: "Currently, there are seats available for sale. All unsold seats will be upgraded on the day of the departure."

Sound like no GUC seats will open up at all in the days/weeks leading up to the flight

RM manages the GUC space. A twitter agent isn’t going to know when or if those seats will be made available.

Wait until a shift change and resend the request.

I had that same message from Delta on twitter but my GUC from LAX-PVG eventually automatically cleared few days ago for a trip less than week and half from now.

People will clear off the waitlist as RM opens up inventory. Unsold seats will go to the gate for clearance of GUCs. I don't even see a point to the OP asking.

That is the theory but in practice I've called in to see that a GUC was correctly applied and was told that upgrade space was available and been upgraded. Maybe it works now, but in the past it was not automatic.

If there are multiple routing options for a specific trip it's prudent to check for GUC space before booking.

For every route, there are busy days of the week and quiet ones. They are not always the same for Y and J. If you have some flexibility and really want to maximize your chances, fly the quiet days. Previously, when my schedule was tight, my upgrade success was less than 50% of waitlisted flights. This year, if I really wanted an upgrade, I booked the flight on Tues or Weds (slowest days between DTW and NRT) and my success rate was 100%. The other plus is that fare can be hundreds less on those days too, making the GUC a super value.