I love the feature. I just wish CO would put zeroes in for fare buckets instead of just leaving them off the list.

I have two CO flights in a reservation and the fare availability looks like this:

F9, FN9, FE9, C9, D9, Z9, ZN9, ZE9, Y9, YN9, B9, M9, E9, U9, H9, HN9, Q9, V9, W9, S9, T9, L9, K9, G9, N9, XN9, X3

and

F9, FN9, FE9, C9, D9, Z9, ZN9, ZE9, R5, Y9, YN9, B9, M9, E9, U9, H9, HN9, Q6

So the first flight has no upgrade availability in "R" right now. I'm a little surprised as there are still 8 open seats out of 16 but ok. The second flight has 5 upgrades available.

-RM