The U.S. Passport Book and the U.S. Passport Card are the premiere documents that denote both citizenship and identity.  The Passport Card, a wallet-sized document, is valid only for entry to the United States at land border crossings and sea ports of entry when traveling from Mexico, Canada, the Caribbean region, and Bermuda.  It is not valid for international air travel.  As of January 23, 2007, citizens of the United States, Canada, Mexico, and the British Overseas Territory of Bermuda have been required to present a passport when entering or departing the United States by air. 

For more information, visit http://www.getyouhome.gov

Tags: Department of State