New York Times
The airlines share little publicly about their loyalty programs, but American and Delta each received about $7 billion from frequent-flier programs last year and United about $6 billion, according to an analysis of financial filings by Jay Sorensen, who runs IdeaWorksCompany, a consulting firm that works for airlines and other aviation businesses.
Those programs are supported in part by the millions of people who use airline credit cards and then earn airline points for spending. The banks that issue those cards buy those points from the airlines in bulk, typically spending many billions of dollars every year.
“What really changed the dynamics of these programs is the arrival of credit cards,” Mr. Sorensen said.