I haven't booked tickets with Alaska or NW and tried the interisland booking, but that is the way most airlines book tickets and that is the way United did it. Except United always used Aloha and other airlines used Hawaiian. Aloha was exclusive to United and could not code share with other airlines. United and Aloha backed each other up if a flight was late, the other airline covered it and waited for passenger or if the delay was too long, one of the airlines had to pay to fly the passengers later. I think that most code share agreements cover things like that. You need to ask the airline when buying the ticket. Sometimes you could buy tickets from Untied and later buy tickets from Aloha and they would still back each other up. However, they would never backup GO and I don't know how things were handled if the interisland flight ran late and the passenger missed their NW, Alaska, or American flight. I would see people flying interisland three hours early just so they didn't' have to worry about it. However, when you have to check out of your hotel in Maui at noon and the flight from HNL to SFO departs at 5:00 p.m., you might as well travel early.