The early experience of the airline industry under deregulation was very much as expected, with increased competition and new entrants offering highly competitive rates. However, there are approximately 130 airlines operating today, and the industry remains more heavily concentrated than it was prior to deregulation. This study reports on concentration in the US airline industry between 1970 and 2009, as measured by the Hcrfindahl-Hirschman Index (HHI) and Concentration Ratio, together with changes in industry costs. The results show a trend of industry-wide reduced costs per available seat mile that is negatively correlated with the increased level of industry output over the last 30 years and increased concentration, which demonstrate the need for more research into the question of scale economies in air transportation.
Johnston, Ahren, & Ozment, John. (2011). Concentration in the airline industry: Evidence of economies of scale? Journal of Transportation Management, 22(2), 59-74. doi: 10.22237/jotm/1317427500