Originally Posted by Ocn Vw 1K

Policies and issues will vary from airline to airline. If the airline offers upgrades which can be confirmed in advance, say by using miles or certificates earned as part of the airline frequent flyer program, the airline will usually make a certain number of upgrade seats available to those who wish to confirm their upgrades as soon as they book. This differs from purchasing an upgraded seat in that the frequent traveller is using a well-promoted benefit of the airline's frequent flyer program to book a coach seat but be able to confirm an upgrade as soon as buying the coach ticket. This is a very important benefit for many frequent flyers. Some use their miles mainly for upgrades. Sometimes "confirmable" upgrades may not clear until later or at the gate or not at all. It all varies on the airline, and the likelihood that the flight can sell booked tickets in first or business classes.