It's completely unacceptable for an airline to do this. If the route doesn't make money, cancel it. Airlines fly empty planes for the same reason the Dennys in East Jesus, Alabama stays open 24 hours, even during the times nobody is around. You have a certain expectation the airline will keep its word at all times - not just when it's profitable. Delta has really missed the boat with this one. Pure leisure flyers may not mind too much, but when I'm flying, I usually have a time certain I have to be at my destination...