The air transport industry has high economic impact; it supports more than 60 million jobs worldwide. Since the early years of commercial air travel, passenger numbers have grown tremendously. However, for decades airlines' financial results have been swinging between profits and losses. The airline industry's aggregate net average profit between 1970 and 2010 was close to zero, which implies bankruptcies and layoffs in downturns. The profit cycle's amplitude has been rising over time, which means that problems have become increasingly severe and also shows that the industry may not have...