You would think that the airlines would want to sell unsold seats on a flight that's about to leave. After all, $50 for a seat is better than no revenue at all if it goes empty. But, it seems that it never works that way. I suppose that airlines are afraid that leisure travellers would stop booking in advance for higher fares if the flexible traveller thought they could get a dirt cheap fare minutes before boarding. It may cost money in the long run.