I see U space all the times on the transcons with the exception of SEA-EWR and to a lessor extent, SEA-FLL....with that said, when I do see U space on SEA-EWR, it tends to be on what I consider the less popular times, like the AM flight from EWR-SEA instead of the PM flight. Honestly, as much as I would like to visit New York, this is partly why I haven't ever flown this route....PHL/BWI/DCA are WAY easier for upgrades and they are pretty fun cities to visit in their own right