The WHTI created the passport card as an alternative for the traditional passport book for land and sea travel only. If you are planning on traveling by air you are required to obtain the traditional passport book.
One exception to the passport requirement is children under 16 years of age. They are only required to have a birth certificate when re-entering the United States. You will need to check with the individual countries you are traveling to to be sure that this is sufficient to enter their country.
The second exception is for U.S. territories, such as Puerto Rico and the Virgin Islands. If your cruise consists solely of U.S. territories a passport is not needed, but documentation such as a birth certificate and driver's license are highly recommended.
The main advantages of the passport card are that it is less expensive and that it will fit in your wallet.
For a new applicant, the passport card will cost a total of $45 in comparison to $100 for a passport book.
There are reasons to consider spending the extra money on a passport book. First and foremost, if you are flying to or from the Caribbean at the beginning or end of your cruise the traditional passport book is required, as this is air travel. Secondly, remember that an adult passport book is valid for 10 years. Although you are only looking at a Caribbean cruise now, your future travel plans may take you farther.
