I use itn to see what fare class to expect on a ticket that I book thru my corporate travel agent. As a Silver, I assumed I was better off to wait until closer to my travel date for a higher class, increasing my chances for an upgrade.

However, on my upcoming March trip, a week ago I saw only Bs, and now there are Qs again this morning. Do fare classes become available in "chunks" - 10 this month, another 10 next month? If so, my theory that booking closer to departure gets me a higher fare class is incorrect.

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.

In November The Zipper and I met in Eagan, MN with the VP of Domestic Pricing/Yield management. They have a complex database of information about historical sales of tickets by fare class and release seats periodically up until the time of departure to get the best yield (price per revenue mile/seat)

It seemed to me that they have a "blended mix" of fares, based on historical data and competitive pressure (what other airlines are selling -- and at pricing competitive w/ other airlines that are competing on the same routes)

This is a very complex process, also award seats are released in small amounts (I wouldn't say "chunks") from 11 months prior to departure date, right up to date of departure (based on unsold inventory and historical sales data)

RC

The above answer is correct. If you have specific questions about how Yield/Revenue Management works, just PM me and I will try to answer them. Typically, as the departure date of the flight gets closer, the lower fare buckets fill up and you would end up with a higher fare buckets. However, if the flight is booking more slowly than expected, the YM system is going to open up more lower bucket availability.

Another key variable is pricing. In very competitive markets, there are some little or no advance purchase fares in relatively low fare buckets. So, theoretically, you could wait, pay more, and still be in a relatively low fare bucket.