American Express thinks so much of the business that it added a fourth Delta consumer card in the latter half of last year, one with no annual fee (unlike most miles cards). And why not, given that the number of new Delta cards it issued in 2017 was up nearly 60 percent from 2014. This week, Citi, clearly feeling the competitive heat, announced plans to add goodies to one of its American Airlines cards, including double miles on all restaurant and gas station purchases. While Citi did not offer up hard numbers like Delta and Amex, the company did tell me that the growth of its American Airlines card portfolio was outpacing the predictions of overall economic metrics. A few years ago, Barclays made an aggressive bid for the JetBlue credit card business and won it. The bank now reports that it has doubled the overall size of the business in two years. So what accounts for the continued appeal of the airline credit card, and who ought to have one? Get the full story at The New York Times Read also "Creating a winning hotel loyalty program"