Beginning on January 23, 2007, citizens of the United States, Canada, Mexico and Bermuda will be required to present a passport to enter the U.S. when arriving by air from any part of the Western Hemisphere. (These countries were previously exempted from the passport requirement in place for the rest of the world.) This is the first phase of the requirements imposed by the Departments of State and Homeland Security as part of the Western Hemisphere Travel Initiative (WHTI). All citizens of the United States, Canada, Mexico and Bermuda must have a passport that establishes the bearer's identity and nationality to enter or re-enter the U.S.
The next phase under the WHTI will address land and sea travel and may be implemented as early as January 1, 2008.