If the 717's aren't flying they would be in for maintenance. As I fly them quite often I think they are fully justified in having 19. There are 4 islands they hop around to and as I've said before, they are usually pretty full of passengers and as mentioned they do a lot of interisland cargo. Remember, if you are in Honolulu and need to go to Wailuku on Maui you can't just jump in a car and drive even though it is less than 100 miles away.