Hi
I have a dining plan with United Air.

I always get emails from other airlines asking me to sign up my credit cards with their dining plans.

If I did do that, would the credit card folks automatically switch everything over to the new airline?

I'm wondering if anyone has ever gotten miles credited to their account on two or more airlines for the same expenditure, whether it be a dining plan, car rental, hotel stay, etc.

Thank you in advance for any response.