I don't know enough about UA to answer that. It's usually available though. OGG and LIH on the 752 seems a little sporadic (seasonality of international routes would explain it -- they refer to that config as the "international configuration", though, really with a range of under 4500 miles they are probably limited to shorter TATL flights, unless they have premium routes to central or south america too?)

HNL on the 772 seems consistently available though.

Honestly, from the West coast, the east coast and Hawaii are more or less equidistant. I'm not sure why Hawaii is not considered premium. It's not like there is any shortage of rich retirees scooting back and forth between Hawaii and the mainland... you'd think that they could sell those seats. At the nicer resorts in Hawaii your hotel folio can make your first class airfare look like a drop in the bucket. Those $16 frozen drinks really add up...