Dumb Little Man reports: "Airlines like money and it turns out that the best way for airlines to make money is to ensure that there are as few empty seats on a plane as possible.
When a person doesn’t show up for a flight, the seat is left empty and an empty seat is a lost opportunity for revenue. As a result of this conundrum, airlines employ fancy statisticians to figure out how many seats the airline needs to overbook just to make up for the no-shows."
Interesting uses of a common airline practice of overbooking flights to get free travel and other perks. Although, you have to be careful using this advice because it can create other conflicts in your travel.