Beginning in June 2009, all U.S. citizens who enter the United States by air, need to present a valid U.S. passport or a NEXUS card, a government-issued travel document. Travelers coming into the U.S. by land or sea need to comply with the Western Hemisphere Travel Initiative (WHTI) and present a valid passport or other valid form of traveler identification that includes a NEXUS, SENTRI or FAST card, or an enhanced driver's license, according to the Department of Homeland Security. Also, a passport is valid for 10 years after the date of issue for U.S. citizens 16 years and older. For children ages 15 and under, a U.S. passport is valid for five years after the date of issue.
For U.S. citizens who are 15 and under, a passport is not required for entry into the United States, but what is required is a copy of his or her birth certificate. To obtain a passport for a child who is under 16 years of age, both parents need to consent to it, according to the U.S. Department of State.
The passport card is a less expensive and smaller version of the passport book. This card meets the specific requirements of the Western Hemisphere Travel Initiative (WHTI) that covers travel to Canada, Mexico, the Caribbean and Bermuda. However, the passport card may not be used when flying to and from Mexico and Canada, and is primarily used for those driving into and out of those countries.
