General question about airline miles as rewards.

[Anonymous]

Long time lurker and I wanted to ask what seems like a very particular credit card question.

When I get mail advertisements for a United or Delta co-branded credit card, I see a rewards structure of something like 2X or 3X miles per $1 spent on these cards for the respective airline (depending on the card of course). However, I have not found an exact description of how these co-branded credit cards from Delta or United earn miles on top of the miles I would earn from just purchasing tickets without a co-branded card. 

For example, I think I earn something around 5 miles per $1 spent on United airfare when I purchase with one of my non-United credit cards. So if I were to purchase a United flight with a United co-branded card, would I get something like 2 miles per $1 from the credit card on top of the 5 miles per $1 from the purchase?

Any insight would be greatly appreciated! I've tried to find this information but have been unsuccseful. It would be surprising to me if the miles from the credit card rewards did not stack with the miles from a loyalty account, but I just wanted to check. I have a young credit card history and so I am trying to be very careful with which cards I try to add. 

[NRB525]

You get the miles to the airline loyalty program without regard to the payment method, whether debit card, another credit card, or co-brand CC. In fact, you would get the Delta miles on the Delta FF program even if you used a United co-brand card to buy the Delta ticket, and vice-versa. 

Separately, you earn extra miles on a co-brand airline card when you buy tickets on that airline. Those points are routed on a delay through the CC issuer, usually when the statement prints each month.  You would earn 1 United mile on the United card in the example above, even when buying Delta tickets and getting Delta miles on the Delta FF program. 

[Anonymous]

Ok, that makes sense and thanks for explaining the rewards structure. This is what I assumed, but I never saw it spelled out like this which is surprising to me.