This OH shift to DTW has 2 things written all over it:

1. Pinnacle strike mitigation through the increase of regional carrier overlap and redundancy.
2. Staging Comair for an eventual merger with Mesaba.

I have been wracking my brain trying to figure out why, in the name of God, Mother Delta would shuffle all the carriers around like this. And these are only plausible explanations I can come up with.