Total revenue was $2.9 billion. So no, it was not the "majority" of their revenue. Also, don't know where that $430 million is coming from (10Q lists $174 million in Mileage Plan revenue for 2Q). The bulk of revenue was passenger revenue at $2.65 billion. My guess is that the payment is being accounted for over several quarters. Further, these CC company payments are not actually pure profit (there is a substantial mileage liability that goes with them). Are they profitable for the airlines? Sure. Are they the "only" reason airlines are profitable? That's a big stretch. Without the ability to actually use and redeem miles, there would be no revenue from the CC companies in the first place.