You would still be able to go there by boat, of course.  Far more fuel efficient than an airplane, but it also takes a lot longer.

Someone else pointed out that one thing they are missing for sustainable living is that they have too many people.  More than the islands can self-sustain, anyways.  Then again, if you bring the stuff in by boat, the energy cost is far more reasonable than bringing in stuff by air.

But if anything goes wrong - volcano eruption, tsunami, race riots, nuclear attack, whatever - you might not be able to escape.  Hawaii really is in the middle of nowhere.  When the longshoremen go on strike, everyone hoards toilet paper.