<P> Since February 1 , 2008 , U.S. citizens may apply for passport cards , in addition to the usual passport books . Although their main purpose is for land and sea travel within North America , the passport card may also be accepted by federal authorities ( such as for domestic air travel or entering federal buildings ) , which may make it an attractive option for people residing where state driver 's licenses and I.D. cards are not REAL ID - compliant , should those requirements go into effect . TSA regulations list the passport card as an acceptable identity document at airport security checkpoints . </P>
what can be used as proof of identity
passport cards passport books for land and sea I.D. cards