The fare war to Hawaii continues. Fares start at $333 round-trip and are available for travel this spring, late summer, fall, and next winter. Airlines that offer the lowest fares will vary by route. Most availability is on American today, but we're also seeing low fares on Delta and United depending on the route.
For most routes, travel is valid on Mondays, Tuesdays, Wednesdays, and Thursdays, in April/May, and again from mid-August through January 2019. Travel to Hawaii appears to be blacked out between December 7, 2018 - January 6, 2019. Not all routes will be available for the entire travel period and some rotues may have more days/week available.
This sale is unadvertised so book quickly if you see something you like. Most third party booking sites will have a 24-hour free cancellation policy so you can think about it for a day.
These prices are what you'll find on the major booking engines. Some third party sites may have slightly lower fares. This is not a complete list. Check flights from your city to see if fares have dropped to Hawaii.