Didn't find an answer when I searched this forum but I'm curious so I'll put it out there to the gurus.

I realize that being waitlisted is based on the surface on availability...but what else is it based on?

I usually upgrade at the minute I can, so last night YVR-YYZ, lots of space, no issues got it right away. This morning I had my alarm set to upgrade YYZ-MIA...I didn't figure in the time difference!!! So I was late by 2 hours. Waiiitttt Listtttttt . But checking the seat map I noticed 5 of 8 J seats are still open and I thought they'd at least auto upgrade to 50% of capacity no?

I've only ever failed one other time when jumping on the opening window of upgrade which was last week YVR-YEG I immediately got waitlisted, then at the gate got it anyway, so fingers are crossed for MIA (since it isn't charging me any extra credits) but I'm wondering if there's a magic algorithm or certain routes, or any light to be shed on when you get waitlisted.