In addition to the plethora of threads found scattered throughout the airline forums pertaining to voluntary and involuntary bumps, be sure to read what’s the secret to booking on oversold flights?, which started as a question by this FlyerTalk member with an appropriate name for this topic: I love the bump.
I can tell you from personal experience that there is nothing like finding yourself having some extra time to reach your destination, only to be offered the opportunity to be voluntarily “bumped” to a later flight, especially if that flight is not much later than the original flight on which you were originally scheduled to be a passenger.
Airlines sometimes overbook flights for various reasons and request volunteers to take a later flight in exchange for some compensation. That compensation can be in the form of a cash voucher, meals, lodging, a credit of an amount of miles or points, an upgrade on your next flight, a free flight, or a combination thereof. The best — and weirdest — thing of all is that when you thank the airline official who gave you the compensation, more often than not that person will thank you because you actually did the airline a favor!
For example, I had received a $300.00 voucher on Northwest Airlines due to volunteering to be “bumped” from an oversold flight. I used that voucher to pay for another flight, from which I again volunteered to be “bumped” due to weight restrictions. I received another $300.00 good for a future Northwest Airlines flight!
With a little planning and a lot of luck, one can actually profit from being “bumped” if one knows which flights at which times stand the greatest chance of being oversold or being restricted due to a weight limit.