Yes, while AA flys out of a different section of Terminal A, it's an easy walk to the mid section where CO's PC is located. You'll just show your AA boarding pass and tell them you're going to the PC. You will have to go through security there, but if you use the far right line you'll end up right at the door to the PC. I often have to fly UA and prefer CO's PC to UA's RCC (free drinks ), I've never had a problem in gaining access and unlike UA or US you don't have to be flying their carrier to use the club.