This document provides an overview of the airline industry. It discusses how rail transportation was dominant until the early 20th century, and how the development of airplanes in 1903 began the rise of air transportation. The airline industry was launched in the 1920s through government subsidies of air mail routes. Major topics covered include types of carriers (private vs for-hire), market structure/competition, operating characteristics, equipment/facilities, costs, and taxes/fees involved in air transportation.