Upgrade To First Class Hawaiian Airlines
Those Passengers who have already booked Economy or Premium Economy tickets may be eligible for an upgrade to First Class based on availability, fare rules, and frequent flyer status. Upgrade to First Class on Hawaiian Airlines -

By bidding for Hawaiian upgrade
By purchasing an upgrade with miles/points or cash.

You can also upgrade to First Class during check-in or at the gate. For more info about Upgrade To First Class Hawaiian Airlines, visit their website or call them. Or For more, you can read the blog at the link-

https://www.airlinesgrouptravel.com/blog/how-to-get-hawaiian-airlines-seat-upgrade