As a shiny new industry with huge growth potential, airlines initially made many investors excited. Over time, however, they became wary, as financial returns fell far short of expectations. A few investment professionals, most notably Warren Buffett, considered airlines difficult to invest in, claiming they have historically operated irrationally and have always been at the mercy of oil prices, unions and new competition.

But now, if you were not aware of their past and looked just at the current numbers, you would find airlines very intriguing.

Since 2013, airline stock prices have soared. Profitability and free cash flow have grown substantially. With more than a decade’s worth of restructuring and consolidation, the airline industry became lean and efficient. New airline management has addressed most legacy problems by focusing on what some refer to as the four Cs. Cowen Securities airline analyst Helane Becker sums up the bullish case when she cites the four Cs