Originally Posted by acjflyer

I think as long as your Delta Amex is linked to the Skymiles account that is linked to the ticket you should be fine - no matter what card you used to pay for the flight. At least that's how I interpret the rules, but I have not had any personal experience, as I get two free bags anyway as a PM.

Originally Posted by mtkeller

You should be good. As long as you can see that you have the card when you log into your SkyMiles account, you'll get the bag free. Doesn't matter what card you use to buy the ticket or you use to pay for the second bag.