Effective October 1, 2007, U.S. citizens traveling by air to Canada, Mexico, the Caribbean and Bermuda must present a passport or other Western Hemisphere Travel Initiative (WHTI) compliant document to enter or depart from the United States. The previous exception, where U.S. citizens could travel by air without a passport upon providing proof that a U.S. passport application had been made, is no longer applicable. As of January 1, 2008, all adult travelers are required to present proof of citizenship, such as a birth certifi cate, and proof of identity, such as a driver’s license, when entering the U.S. through land and sea ports of entry.