Some of the largest and most popular airlines in America are Delta Air Lines, Southwest Airlines, United Airlines, American Airlines and JetBlue. Some other popular American airlines include Alaska, Virgin, Spirit, Frontier and Allegiant Air.
Most of the major airlines that operate in America focus on domestic routes, as they don't have to compete with international airlines in this area. Many of them do offer some international flights, however.
American Airlines was founded in 1928 as American Airways. The company now carries over 100 million passengers annually and has about 3,500 daily departures from 273 locations in the United States. American had a high-profile merger with US Airways that concluded in 2015.
Delta Air Lines began as a crop-dusting company in 1924. The airline now carries over 170 million passengers per year and flies to 334 destinations in 64 countries with a fleet of over 700 aircraft. The largest hub is in Atlanta.
Southwest Airlines is known primarily as a budget domestic carrier, but also has a small amount of international flights. The company operates over 3,600 flights per day to 94 locations. The company boasts the largest fleet of Boeing aircraft in the world and 42 consecutive years of profitability.