A survey of U.S. and foreign travelers departing the U.S. as a means of obtaining data on visitor characteristics, travel patterns and spending habits, and for supplying data on the U.S. international travel dollar accounts as well as to meet balance of payments estimation needs. The IFS covers about 70 percent of U.S. carriers and 35 percent of foreign carriers, who voluntarily choose to participate. Sample results are expanded to universe estimates to account for non response of passengers on each sampled flight, for coverage of all flights on each major airline route, and for all international routes. The basis for the expansion is the number of passengers departing the United States, obtained from the U.S. Citizenship and Immigration Services Bureau (formerly, the Immigration and Naturalization Service).