Delta Air Lines, Inc. (DAL) ("Delta"; NYSE: DAL) is a major American airline, with its headquarters and largest hub at Hartsfield–Jackson Atlanta International Airport in Atlanta, Georgia. The airline along with its subsidiaries operate over 5,400 flights daily and serve an extensive domestic and international network that includes 334 destinations in 64 countries on six continents, as of June 2015. Delta is one of the four founding members of the SkyTeam airline alliance, and operates joint ventures with Air France-KLM and Alitalia, Virgin Atlantic, and Virgin Australia. Regional service is operated under the brand name Delta Connection. Delta is the sixth-oldest operating airline by foundation date, and the oldest airline still operating in the United States. The company's history can be traced back to Huff Daland Dusters, founded in 1924 in Macon, Georgia as a crop dusting operation. The company moved to Monroe, Louisiana, and was later renamed Delta Air Services, in reference to the nearby Mississippi Delta region, and commenced passenger services on June 17, 1929. Among predecessors of today's Delta Air Lines, Western Airlines and Northwest Airlines began flying passengers in 1926 and 1927, respectively. In 2013, Delta Air Lines was the world's largest airline in terms of scheduled passengers carried (120.6 million), and the second-largest in terms of both revenue passenger-kilometers flown (277.6 billion) and capacity (4.4 billion ASM/week; March 2013).