If you plan to rent a vehicle on the Island we HIGHLY recommend using Turo. We have found many Turo rentals available for pickup directly from Hilo Airport and Kona Airport and they typically are more affordable than renting from rental car agencies. It also help locals make an income which we very much support! Book early as rentals will fill up for January fast
If you are traveling from the west coast, this is the best option for flights to Hawaii. You could potentially get your one of your flights for free if you sign up for a Hawaiian Miles Credit Card and spend $2000 on purchases with it in the first 90 days which would give you an automatic 70,000 miles. Flights from the west coast are on average about 45,000 miles round trip per person.
See Card Details at:
https://cards.barclaycardus.com/banking/credit-card/hawaiian-air/mastercard-mastercard-world-elite/banner/e1dbe7c3-e370-4f62-b2bf-2bdfdce533df/?referrerid=PTRBAHomeMA
If you are coming from the east coast, Southwest is the best option for flights to Hilo or Kona. Unfortunately Hawaiian does not serve the east coast of the United States.