The airlines today are filling up close to 85% of available seats. Recently, Delta has made a new feature for the people coming on board the plane. The airline has added a new trait that lets people pay an extra to give a spot next to an unsold seat. Delta’s move to get ” money for nothing” addresses a problem for the business. As every seat for an airliner counts as a sum of the total revenue, this new feature Delta proposed is stopping them from getting their potential revenues. To explain, by letting someone buy off another empty seat with such a relatively cheap price compared to another potential buyer for the seat that would pay even more, Delta would not only lose from the money gained by the seats but also on trivial matters. For instance, in an airline, they serve drinks that needs to be paid. When people who board the plane buy off the seats, there would be not as much customers to buy the drinks than when all the seats are full with people.

http://business.time.com/2013/10/07/6-outrageous-fees-the-airlines-havent-though-of-yet/