On the plane, the access through which the passengers enter and exit is a particularly egregious mock-up of an airplane door, probably built out of wood and canvas, that patently would not remain airtight during a real flight.
Cheever says he and his companion won't have to pass through customs in Hawaii, which is why he's "glad they made it a state." State or not, Hawaii was always United States territory, and American citizens were never required to use passports or pass through customs checks to enter.