Guam is served by the Antonio B. Won Pat International Airport, which is a hub for United Airlines. The island is outside the United States customs zone so Guam is responsible for establishing and operating its own customs and quarantine agency and jurisdiction. Therefore, the U.S. Customs and Border Protection only carries immigration (but not customs) functions. Since Guam is under federal immigration jurisdiction, passengers arriving directly from the United States skip immigration and proceed directly to Guam Customs and Quarantine.