I'll bump this thread for a related question rather than start a new one.

What are the odds of such an upgrade clearing in people's experience? Is there any way to determine in advance which flights are most likely to clear -- like some airlines having certain fare codes for upgrade availability. If there are any Z fare availability does that mean the upgrade is likely to clear?

Are certain days of week easier to clear? Certain equipment? Certain times of year?


The routes I might be interested in would be FRA-YUL, FRA-NYC, and FRA-SFO. If I had to guess I would guess YUL would be easier than the other two but have people had success to SFO? Is it harder to get the red-eye upgrade than the daytime?