Mokulele Airlines flies the Cessna Grand Caravan with one propeller engine and 9 seats.
Ohana Airlines (a division of Hawaiian Airlines) flies the ATR42-500 which has two propellers and 48 seats.
Hawaiian Airlines flies the Boeing 717 with two jet engines and 118 to 123 seats.
The above information is as of 2017. Airlines and aircraft can change, so call each airline to verify the types of airplanes that they are currently flying.
See photos of these airplanes below.