San Diego International Airport (IATA: SAN, ICAO: KSAN, FAA LID: SAN) is the primary international airport serving San Diego and its surrounding metropolitan area, in the U.S. state of California. The airport is located three miles (4.8 km; 2.6 nmi) northwest of downtown San Diego. It is the busiest single-runway airport in the United States and has a relatively small footprint, covering 663 acres (268 ha; 1.036 sq mi) of land. The airport is a hub for Alaska Airlines. The airport is owned and operated by the San Diego County Regional Airport Authority. It operates in controlled airspace served by Southern California TRACON. The airport's landing approach is close to the skyscrapers of downtown San Diego, and can sometimes prove difficult to pilots due to the relatively short usable landing area, steep descent angle over the crest of Bankers Hill, and shifting wind currents just before landing.