It is possible, but you (obviously) need to be flexible and lucky.

I went to Kona last week. Everything else on United has been nearly or totally full all summer for all the islands, with the possible exception of midweek travel to Honolulu.

I tried to fly United on Sunday 7/1 back to the west coast and would have been stranded. I had to fly SA on Hawaiian to get back, and I was lucky to do that.