Going from Hilo to Kauai on a Sun afternoon. How long before flight would you recommend to arrive at airport check in?

I suspect about the same as any domestic flight these days,in theory at least, give them a call or check website. Have fun.

I just called Aloha airlines this week about my flight from Oahu to Maui. I was told if it is just inter island, then an hour is sufficient.

Depends on the day and the crowd. We flew recently midweek to Maui and an hour was sufficient. We also flew to Kauai in May on a Friday morning and we barely made the flight after arriving two hours early.

A few weeks ago went from Kauai to Oahu on Hawaiian Airlines and it only took us about an hour, but it was an early morning flight (9:00 a.m.).

I booked flights for August on Aloha and for a friend on Hawaiian (flight to Maui leaving from Kauai. I was told 90 minutes for interisland flights on neighbor islands and 2 hours for anything leaving out of Oahu. There are four military bases on Oahu I think this makes them a vulnerable target and airport security is high.