Delta Air Lines is a major airline in the United States and a legacy carrier. It is headquartered in Atlanta, Georgia. The airline, along with its subsidiaries and regional affiliates, including Delta Connection, operates over 5,400 flights daily and serves 325 destinations in 52 countries on six continents. Delta is a founding member of the SkyTeam airline alliance. It has nine hubs, with Atlanta being its largest in terms of total passengers and number of departures. It is ranked second among the world's largest airlines by number of scheduled passengers carried, revenue passenger-kilometres flown, and fleet size.