Originally Posted by fromYXU
This is very complex. If NW believed that they could sell all seats as full coach you will only see availabilty for Y. That is rarely the case. They know that some %age will need to be sold at different fares. They constantly review this. For example, if 10% the fares are sold as cheap fares and they sell 6 months before departure but nothing is selling after that point, they may choose to add more cheap fares at later in order to sell out the flight. I suppose it is supply and demand. I doudt that there is anything linear about it!
Exactly. It's about as far from linear as you can get.
In fact, you can sometimes see the inventory shift substantially throughout the day, as a handful of bookings or cancellations can push the flight to a different threshold, which results in shutting down or opening up signifcant inventory in some buckets.