I'd previously seen Mileage Multiplier offered when looking at itineraries both ticketed and on hold, but despite opting for them, it never took a credit card for them, so I purchased an award ticket for a flight within 24 hours (so I could check in right away), and as soon as it ticketed I pulled it up on the AA web site, thinking I might need to check in for the Mileage Multiplier to take my card, but this time as soon as I opted for Mileage Multiplier it asked for a credit card. Once I saw the charge as pending on the AmEx web site, I cancelled the award ticket. It took a couple of days for the charge to convert from pending to posted, and then another three days, but the Airline Fee credit did post for it. Here's how the Mileage Multiplier charge looks on the AmEx web site (as an add/collect):
