Since 2007, there have been four major airline mergers. As a result of this consolidation, about 85 percent of passengers in the U.S. flew on four domestic airlines in 2013. Certain industry observers have raised concerns that consolidation could have adverse effects on airline competition, such as higher airfares and reduced service. Others argue that consumers stand to benefit from recent changes in the industry as profitable airlines reinvest in new planes and expand their networks. This book addresses changes to the financial health of the U.S. airline industry since 2007; changes to the structure of the market since 2007; how consumers have been affected by these changes; and views of stakeholders on the key challenges to airline competition and actions the federal government could take to address these challenges. This book also presents the results of analyses of the relationship between competition, measured at the individual route level, and airline service quality, also measured at the individual route level.