Originally Posted by RobOnLI

EF no longer offers award and upgrade inventory for most *A carriers including UA. AC/TK/A3 still offer some visibility but I don't usually search those so I can't say how good the data is. EF removed this data months ago.

To use TK points on UA you need to look for "X" (Coach) or "I" (Business) for award inventory. I honestly do not know if that translates to being bookable by partners or not but those are the base fare codes needed to book an award ticket. You can create a profile on United.com and enable "Expert Mode" which will give you access to this data on flights you're looking for. Note: you should search segment by segment instead of multiple segments at the same time if you want to see this data reliably.

-RM