One thing that must be a constant though, comes in the form of air travel - we all enjoy being upgraded. Whether you normally travel in economy, or business class, it is always something that comes as a pleasurable surprise when we learn that we have been upgraded, at no cost to ourselves. Although pleasurable, and not something that most of us would turn down, upgrades can be a rather damaging thing. The same applies to a certain extent from business to first. The upgrades are also used as a loyalty bonus and a way to say thank you for your business, or if you want the truth - a way to get the airlines out of a spot of trouble because of over booking.
Most airlines upgrade passengers because they overbook their flights.
This happens because the airlines have to count into their figures a certain amount of cancellations and a few no shows, when the passengers do turn up then the airline needs space, especially at the back of the plane and this is when the upgrading begins. The first thing you need to do is join the airlines frequent flyer programme. Joining the club is free and normally will mean points for each mile of travel earned, and lots of other bonuses that can be used towards free flights and other goodies. Regarding upgrades, then the holders of the airlines frequent flyer club will have priority. That is to say if the airline needs to upgrade, then they will check who is a member and then upgrade them subject to their status.