Originally Posted by wijibintheair

Question on this after reading a few of the posts above:
Let's say AA is your primary card - you reach EXP and then decide to reach lets say silver status on BA as a back-up. Now reading the threads above a couple say that you do this to enable lounge access in the US. What is the situation though if I book a flight lets say JFK - MIA on AA metal with an AA number - do I need to have my BA card number entered for that booking to gain access to the AC, or do you still use your AA number - i.e. chance of upgrade, bonus miles etc and just present your BA card at AC for access - surely that would not be allowed? Just curious!