Originally Posted by
YouGoGlenCoco
Standby is only an option for Pualani PLT, GLD, Corporate Ticket Holders, and those who purchased Hawaiian Coach Plus.
Any changes must be made via UA, since you booked your ticket through them. Also - they have control of your ticket, the HA agents won't be able to make any changes to it.
While the earlier flights are there, it's quite possible that they were not available for sale via UA Codeshare.
Interesting that they don't mention standby options for pax on biz/first class fares. Intuition tells me that those fares would bring some flexibility, of course intuition rarely matters with airline rules.