Since I am not a student of economics, sometimes reading other people's analysis on market situations is enlightening for me.
Say for instance, AD's analysis on the AirAsia 2,000,000 free tickets. I didn't think of the, not so popular, yet unoccupied seats, but since the customers are paying for the airport tax (which is about 40 % of total charges), the operational costs are covered (or less for Air Asia to cover in this aspect, that is).
A way to lower the marginal cost of operations for Air Asia. Well, it works both ways. The same way where cinemas give the vouchers for buy one, free one tickets for the less popular movies, or charge less for matinee shows or in the morning, so that more people would come and watch. Of course, at night it does not make sense to do that as it will lower the margin of profit for the company, as everyone is flocking to the cinema. Comprende?