Maybe someone in Delta got smart and figured out that having 8 different companies flying their passengers around providing subpar service is more expensive than actually just flying the airplanes with their own staff. The redundancy in mechanics, management, scheduling, HR and all the other departments means that Delta is paying much more than they would have to if they staffed the plans themselves. Delta is, after all, an airline - in business to fly passengers around in airplanes. I wonder how big of a team Delta has to have internally just to deal with the DCI carriers.