The airlines industry provides air transportation for passengers and cargo by using aircraft such as airplanes and helicopters. The origins of flight date back to 400 B.C., when the Chinese invented the kite, which was used not only for fun but also to test the weather, and for later development of balloons and gliders. In the 1480s, Leonardo da Vinci was fascinated by the thought of flight and drew pictures and designs of his theories of flight and flying machines. The first recorded flight was in 1783, when two French inventors flew the first hot air balloon, and the Wright brothers successfully flew the first airplane in 1903.

The airlines industry is structured into three main components: commercial, general, and military. Commercial aviation includes national carriers such as Delta and American, and regional carriers like GoJet and SkyWest Airlines. Commercial airlines may also focus on other areas of business, such as crop dusting, fighting forest fires, and rescue operations. According to the trade organization Airlines for America, commercial aviation helps drive more than $1.5 trillion per year in U.S. economic activity and more than 10 million U.S. jobs. General aviation includes personal and business or executive flights and flight instruction. The subsectors of the airlines industry include operations, maintenance, marketing, and finance divisions. 

Air transportation may be scheduled or nonscheduled. Most commercial airlines operate according to a schedule, flying regular routes, even if the plane isn't full. Air carriers that don't operate based on a schedule usually fly during offpeak hours, and usually have more flexibility regarding choice of airport, flight times, and load factors. Nonscheduled carriers offer charter flights of passengers, cargo, or specialty flying services. In 2018, Hartsfield-Jackson Atlanta International Airport in Atlanta, Georgia, was ranked the busiest airport in the United States, with nearly...