Changes to upgrade list between T4 and boarding time
 

When new people are added to the airport upgrade list in real time, is that because they are checking into the flight for the first time, or is it necessarily because they’ve newly requested the upgrade just hours before departure?

Could be either but yes ppl are added to the list as they check in. Also as they change flights onto your flight whether by SDC or otherwise

+1

Most likely they are moving from other flights onto yours.... IRROPS, SDC.

Rare that people who have been on the flight for days/weeks/months and decide to upgrade @t-4. and at the top of the list, you have EXPs who are auto-upgraded at time of ticketing.

for whatever reasons AA and the TSA are convinced I'm sketchy, so 90% of the time OLCI doesnt work on international flights. As a result i can only do so on arrival, at which point I get added to the list and jump up somewhere near the top (for the domestic segment if I'm in Y and didnt clear the upgrade)

More than likely, it is people checking in for the flight for the first time. I usually check in about 1 to 2 hours before the flight and if I'm not already flying F or J, only at that point do I show up on the upgrade list, usually im somewhere between 1 and 3 in the list. So regardless of when anyone requests the upgrade (automatically at booking for EXPs and PPs,) they only show up on the list when they actually check in for it.

good point

This.

I usually check in around 90 minutes prior to departure and my name pops up on the upgrade list - usually near the top. I assume that the pax I jump ahead of on the list are a little dismayed when it happens. Then again, it happens to me too...

I was that guy a few weeks ago, and then someone else was that guy to me. (Spoiler: It all worked out anyway.)

I SDC to an earlier ORD-PHL (foregoing that upgrade) and was added to the list in the AC at T-90 or so. Went right to #1 on a list with >15 names for J1 availability.

When I checked at T-50 as I was preparing to leave the club, I saw that I was #2 on the list.

Of course, #1 clears at the gate (I even heard them page by name before boarding). I go ahead and board with Group 3, and then get the battlefield upgrade before departure as #1 never showed.

I check-in from the security line - so I'm obviously not doing it right!