The history of inspecting U.S.-bound passengers in foreign countries began in 1894, when American immigration inspectors were deployed to sea ports in Canada. Modern preclearance facilities were first introduced in 1952 at Malton Airport (now Toronto Pearson International Airport) and Calgary International Airport under an informal arrangement with the government of Canada and are now available at eight major Canadian airports and one seaport, while several other seaports and one rail station in British Columbia have "pre-inspection" facilities for screening immigration admissibility only. Preclearance facilities also exist in airports in Aruba, the Bahamas, Bermuda, Ireland, and the United Arab Emirates.
多伦多机场数千人滞留 乘客被“蹊跷“引导跨过美国海关