While this is a great benefit for those who pay cash for tickets, I'm struggling to see how it makes sense for Amex. At 5x, even if you value MR at 1 cent each, that's 5% back. There's no way their swipe fees are that high, so this is a loss leader for them. The point of a loss leader is to get people to also buy other products that they can make money on, but I don't think this will increase spending in other categories. People will put their airfare on the card and continue to use other cards for everything else. Perhaps a few people who fly often will sign up for the card specifically for this benefit, but they are likely to cost Amex a lot unless the benefit is capped. I'm just not seeing how this is going to be sustainable.