Not all MR worthy, but if you are headed south, DL looks to be going hard at AS on premium cabin US west coast to Mexico.
In addition to the CUN fares posted, SEA-PVR is about 1/2 the price on DL (mid $700 range) as it is on AS ($1350).
Edited to add: looks like these DL fares are all UP fares, so they are selling eco tix with upgrades to front cabin, maybe because they have poor sales for front cabin?