I thought about this a bit too. I researched the fall of Comair and from what it seems, the situations are completely different. While yes both Comair and Endeavor were/are wholly owned by Delta, the approach by Delta is completely different.

Comair was a successful company for many years and was able to turn large profits. However, post 9/11, things went sour everywhere. Delta's approach to running Comair was mostly laissez-faire, or hands off. They used an aging computer system which caused a crash during Christmas eve, which crippled the Delta network for days. Things just got worse from there and finally they pulled the plug.

Pinnacle, Mesaba, Colgan etc., had a similar fate, but the bankruptcy restructuring allowed them to emerge as a Delta WO'd, but this time, Delta took over everything, from checklists to uniforms, etc.

Correct me if I'm wrong, but the current fate of Endeavor looks a lot brighter than that of Comair's, simply because of Delta's involvement with the company, which is the opposite of how they ran Comair.