Convention code on *A
 

I am attending a convention in BNA, for which I have a promo code for travel on CO. The cheapest flights are on US and that's where I want to credit my miles. Is there a way within *A that I can use the CO code, but fly on US metal? I know once before I booked a US award ticket from the CO website and using CO miles. But when I search CO, they only give me their flights, not those in *A.

Any help is appreciated.