AeroMexico
I went to Cancun in April on DL/AM :
BOS - CVG Delta
CVG - CUN AeroMexico
It was a morning flight in Economy in AM and let me tell you the inflight service (food) is better than what you can get in Delta FC. Even enjoyed a movie (Spanglish), on a TV monitor that is actually sharp and focused. The 737 was clean and new. Service was also attentive and efficient.
Have fun.