Any U.S. citizen traveling by air within the continental U.S. is required to carry either a valid passport or a REAL ID in order to comply with the REAL ID Act. Most REAL IDs have a star on the top right corner of its state-issued driver’s license or identification card signifying compliance, however, a few states (Hawaii, Tennessee, Ohio, and Utah) have issued compliant REAL IDs without a star. You can learn more about the REAL ID here.