The passport card is an alternative to an ordinary U.S. passport booklet for land and sea travel within North America (Canada, Mexico, the Caribbean, and Bermuda). Like the passport book, the passport card is issued only to U.S. citizens and nationals. However, the passport card cannot currently be used for international air travel.
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The passport card is being issued by the United States Department of State in response to border community residents' needs for a less expensive and more portable alternative to the conventional booklet since the Western Hemisphere Travel Initiative's requirements for travelers to carry a single document verifying both identification and citizenship have come into effect. In an effort to improve efficiency at land crossings, the passport card also includes a vicinity-read radio frequency identification chip with a unique identifying number tied to government databases; unlike the passport book, the RFID chip in the passport card is designed to be readable at a greater distance and will not contain any information from the MRZ of the passport card beyond the identifying number. To prevent the RFID chip from being read when the card is not being used, the passport card comes with a sleeve designed to block RFID while inside.[3]
Under the REAL ID Act, the passport card will also be accepted for federal purposes (such as domestic air travel or entering federal buildings), which may make it an attractive option for people living in states whose driver's licenses and ID cards are not REAL ID-compliant when those requirements go into effect. TSA regulations list the passport card as an acceptable identity document at airport security checkpoints.[4]