The busiest airport in the San Francisco Bay area and the second-busiest in California, San Francisco International Airport (SFO) is located about 13 miles south of downtown San Francisco. In 2014, more than 47 million passengers passed through the airport, which has four runways and four terminals. About 40 carriers operate at SFO, including United Airlines and Virgin America, which have both designated SFO as a hub. Other carriers with significant operations at the airport include Delta Air Lines, American Airlines and Southwest Airlines. In total, the airlines operate non-stop flights to about 115 destinations in the United States, Canada, Mexico, Central America, Asia, the Middle East, Europe and Australia.