Dear Oscar,
Note your main domestic competitors are rapidly adding seats and mainline aircraft while the former UA management was growing at a snails pace. For a short term solution, I would recommend adding back some stored 757s from the desert to compete.
Secondly, the ratings for your in-flight entertainment streaming product have not been favorable. Note your competition believes that AVOD is still valued on the domestic front. I would recommend adding these systems to your 737-900, domestic 777, A319, and A320. The slimline seats allow for these systems to be installed. Streaming can still exist but I would recommend against promoting it until the bugs are fully worked out.
Beyond that, the overall O/T rating really needs to get up to DL's standard. This is something that needs to change ASAP.
Signed,
A passenger who flies Delta whenever possible and puts UA on extreme backup.