Delta had $4.8B in profit in 2024 but only $1.9B came from "other revenue" which not even all of that revenue is from co branded cards. Also much of that also has a cost associated with it, since its cost money to fly those people around, even if they are being paid the revenue of the ticket from a credit card company instead of the passenger itself. Also its not like the passenger just would not fly without the deal. A large portion of those people would still pay to fly, but instead they are trading miles earned on credit cards for flights.

Actual marginal profit from the CCs is probably $1B so even without the cards Delta is still probably close to $3.8B for the year.