Aloha Airlines.... or.... Hawaiian Airlines... Both are good, but if I had to choose, 'Aloha' ;-)
Best way to get around would be to hire a Convertible or A Harley ;-) There are also buses, if you prefer not to hire your own transport.
On the island we don't have ferrys...so the only way to go is fliing, you can buy a cupon book from hawaiian with 6 one way ticket for arround 360$ and can be parchase at the airport
No bus system like oahu...young kids hitchaike...but the best way is on 4 wheel drives, Baget rent a car have good deals in the inter net for a truck for only 19$ a day...it is best to get it at the airport, a taxi to town is very expensive.
I flew AA.... This is a loooonggg flight!!! I flew from Philly to Dallas to Oahu to Kona. 12+ hours!! It was worse than my trip to Brazil.
I was also sick so that didn't help any!!
Rent a car!!! It's an island with one highway!! you can't get lost... If you do, ask!! Very helpful people!!