JetBlue Airways ( JBLU 2.38% ) posted a string of incredible earnings results following the rollout of its Mint premium transcontinental service in 2014. More recently, the popular low-fare carrier fell into a bit of a rut, with slowing revenue growth and rising costs combining to pinch profits. As a result, adjusted pre-tax income -- which peaked at $1.2 billion in 2016 -- receded to just $654 million last year.