Effective January 22, 2018, air travelers with identification (ID) that does not meet the REAL ID Act requirements or whose state does not have an extension must present an alternative form of ID in order to board a domestic flight. The U.S. passport card and passport book are both acceptable forms of ID.
Check the REAL ID compliance status of your state and review TSA’s list of acceptable forms of identification. You should also check with your state’s licensing agency about how to acquire a REAL ID-compliant identification card.
Examples of acceptable forms of ID after January 22, 2018 include a U.S. passport book or passport card, U.S. military or dependent ID, DHS trusted traveler cards, airline or airport-issued ID, and federally recognized tribal-issued photo ID.
The U.S. passport card and passport book are both U.S. passports. The passport card cannot be used for international air travel, but is great as ID for domestic air travel. Here's why: