A gateway is a port of entrance or exit for international merchandise trade between the United States and other countries.
Air data for specific airports may include a low (generally less than 2-3 percent of the total value) level of small user-free airports located in the same regional area. In addition, data for nearby individual courier operations are included in certain airport totals to prevent disclosure. Land port totals include trans-shipment data. Port totals reflect the mode of transportation in use at the time the shipment entered or exited a U.S. Customs port.