This article surprised me:
Delta Air Lines is considering a plan to eliminate its Song discount-airline unit, but the carrier would draw lessons from its experience with Song to spruce up its primary flights with satellite-television screens and other popular amenities.
later in the article
Song workers already have been told that Delta plans to merge their employee roster and seniority list back into Delta's, which would be one of the first steps toward eliminating Song. Delta executives aren't considering abandoning the two-class service now used on Delta planes, since it helps to lure higher-revenue business travelers and other passengers eager to use frequent-flier miles to upgrade to first-class seats. Song's one-class service has worked mostly because the unit concentrates on leisure routes.