Originally Posted by GUWonder

Some airlines have a benefit, negotiated or otherwise, to allow some people to get booked into rather expensive full fare economy class fares on sold-out flights with otherwise no space available for sale to the general public.

I have had some carriers book me onto flights that weren't available for sale to the general public (i.e. all available inventory on the sold-out flight was zero in the systems used by the airlines and travel agencies), and I think we were required to put in such requests at least 2-72 hours in advance of scheduled flight time.

SkyTeam, for example, has as benefit for ElitePlus members a supposedly guaranteed benefit to book economy class seats on sold-out SkyTeam carrier flights as long as the request is made 24 hours in advance of scheduled departure. It's booked as full-fare tickets with fare basis such as Y, YO2, YD, and Y2, and so it tends to be anything but cheap.