Originally Posted by
chitownflyer
I called LH MM and the agent told me there is NO method to search for upgrade inventory in advance. One has to make the request and hope for the best, but there seems to be a correlation between award space for free C & F tickets and upgrade award space.
Obviously very small sample sizes, but in my experience if UA shows a free award ticket, that means your upgrade will clear immediately. However, the opposite is not necessarily true. As I've had a C>F upgrade clear immediately when no F award space was available to UA (didn't check *A or MM).
If you're concerned with absolutely clearing at booking, then I would assume you could buy the ticket on UA, and try to upgrade. If not, cancel under the 24 hr free cancellation policy.