Seeking to book a DCA-YUL-YVR trip using United miles on AC metal. The first leg shows J availability but the second does not. This is for a trip in about 2 weeks. I can see from an AC search that there are open seats in J on that second leg, though not a ton (looks like 8 of the 32 J seats are selectable with the rest occupied). Can I expect them to be released for booking via United at some point?