Question: can a passport card be used for domestic air travel

Answer: Yes, The U.S. Passport Card is the de facto national identification card of the United States and a limited travel document issued by the federal government of the United States in the size of a credit card. Like a U.S. passport book, the passport card is only issued to U.S. citizens and U.S. nationals exclusively by the U.S. Department of State and is compliant to the standards for identity documents set by the REAL ID Act and can be used as proof of U.S. citizenship. The passport card's intended primary purpose is for identification and to allow cardholders to travel by domestic air flights within the United States and to enter and exit the United States via land and sea between member states of the Western Hemisphere Travel Initiative (WHTI). However, the passport card cannot be used for international air travel.