"So long, Oahu!"

ALOHA

This common Hawaiian greeting can also mean "goodbye" and is often heard at the start or end of a visit to the islands.

This clue plays on the double meaning of "aloha," which is both a Hawaiian greeting and a farewell. "So long" hints at saying goodbye, while "Oahu" points to Hawaii, where "aloha" is commonly used. The wordplay cleverly combines the farewell sense with the Hawaiian setting to lead to the answer.