American Airlines is the my favorite airline out of the big 3, some of this may be bias on my behalf as one of my local airports is one of their biggest hubs but that aside. They have an amazing livery that works well on their aircraft especially the Boeing 787 Dreamliners, B777-300ER and the very cute Boeing 737MAX8.
Not to mention that their biggest and my favorite strength against United and Delta is their big Latin America presence. While DL and UA manage to have a few services, AA completely DOMINATES the region with their only true US competitor being Spirit Airlines of all things.
American Airlines Boeing 737MAX8s in Miami with the one in the background taking off for Cali, Colombia with one in the foreground resting at gate D42.