Interestingly, learned about Aeromexico’s classic fare when I was booking an Atlanta to Leon Mexico first class fare this week. I booked it on Delta.com, Delta to Mexico City, Aeromexico to Leon. Same carriers returning. Clicked on Delta First Class column that said First Class/Classic. At time of booking figured “Classic” was Aeromexico’s First Class within Mexico. We’d booked first class through Mexico City DL/AM in the past to Puerto Vallarta and was first on both carriers. It appears now on these connections, only Delta portion is first class and you are in coach “classic” on Aeromexico. In order to get Aeromexico’s “Premier” or first class seating, you now have to pay to upgrade on the connecting Aeromexico flight and have to do so on the Aeromexico website . Checked several itineraries and seems to be the case on all itineraries where Delta to Aeromexico is the connection through a Mexico City.