Here’s a new one for me:

T-72, purchase SFO-JFK, H class, basically the typical close-in full fare (~$500).

T-24, check in, still no upgrade, looks like 2-3 seats free in F. 4 people ahead of me on the waitlist which is unusual (75k and used to being first, especially with close-in fares).

T-1.5, nobody has moved on the waitlist. On a lark I check availability by booking and see a 75k U fare is available, for the same price as my original fare. So I cancel original ticket, book a new one, and boom, instantly upgraded.

So how did I get away with this? Given the fare costs were the same, shouldn’t I have just been moved up when U space was released? Is this just a regular kind of upgrade processor goof?