The Western Hemisphere Travel Initiative (WHTI) is a program implemented by the U.S. Department of Homeland Security (DHS) to improve the security of travel documents and enhance the security of international travel to and from the United States. The WHTI requires that all travelers, including U.S. citizens, present a passport or other approved document when entering or re-entering the United States by air. The WHTI was implemented in response to the recommendations of the 9/11 Commission, which called for improved security measures for international travel to the United States. The program is administered by the U.S. Customs and Border Protection (CBP) agency within the DHS.