San Francisco International Airport (IATA: SFO, ICAO: KSFO, FAA LID: SFO) is an international airport located in an unincorporated area of San Mateo County, California, United States, about 13 miles (21 km) south of San Francisco. It has flights to points throughout North America and is a major gateway to Europe, the Middle East, Asia, and Oceania. SFO is the largest airport in the San Francisco Bay Area and the second-busiest in California, after Los Angeles International Airport (LAX). In 2017, it was the seventh-busiest airport in the United States and the 24th-busiest in the world by passenger count. It is the fifth-largest hub for United Airlines, functioning as the airline's primary transpacific gateway, and is a major maintenance hub. It also serves as a hub for Alaska Airlines. The airport is owned and operated by the City and County of San Francisco and lies in a ZIP code assigned to San Francisco. However, it is located outside of San Francisco in unincorporated San Mateo County. Between 1999 and 2004, the San Francisco Airport Commission operated city-owned SFO Enterprises, Inc., to oversee its business purchases and operations of ventures.