If you are a U.S. citizen traveling from the mainland, you do not need a passport or "papers" in the international sense, as Hawaii is the 50th state. However, as of May 7, 2025, you must have a REAL ID-compliant government-issued identification (usually indicated by a star in the top right corner of your driver's license) to board a domestic flight. If your license is not REAL ID-compliant, you will need an alternative "paper," such as a U.S. passport book, passport card, or permanent resident card. For non-U.S. citizens or international travelers, you must have a valid passport and, depending on your country of origin, an ESTA or a visa to enter the United States. It is also important to remember that Hawaii has strict agricultural declarations: you will be asked to fill out a form on the plane declaring any plants or animals you are bringing, as the islands have a delicate ecosystem that is heavily protected by state law.