Suppose ITN gives the following (made up numbers):
F4 I3 A2 G1

Does that mean there are *actually* four seats in first available, of which one is reserved for full first fare, one is designated for either full first fare or an upgrade from full coach fare, one is designated as for either full or discount first fare or upgrade from full coach, and the last seat will go to anybody who pays or gets an upgrade from any fare? In other words, do the fare codes correspond to concentric venn diagrams?

*If* the above is true, then what happens immediately before departure, supposing that none of the above seats were taken by anyone earlier? Would the codes suddenly become F4 I4 A4 G4, since *just* before departure there would no longer be any reason to reserve seats for higher fare codes?

As a lowly silver, this question interests me because I am wondering whether if a flight is G0 I could still (theoretically) get upgraded at the gate even if there aren't any no-shows, if it is F(number>0). Obviously golds and CPs take precedence, but I am trying to figure out if those F/I/A seats eventually become available as G, or whether when I am put on a waitlist I am only hoping for someone with a G seat to be a no show.

At the gate or 1 hr prior to departure, those seats, whether F/I/A/G/D, get dumped into one pool. Then the gate agent clears the standby list based on status from highest(CP) to lowest (SP/non pref).

F4 I3 A2 G1
There are 4 first class seats. The G seat is for upgrade from restricted fare under the 7/3/1 day in advance rules. The 2 A seats are the automatic bump from a y fare (like a a4coach fare) The 3 I's are for immediate upgrades for CHP, Gold and Silver who have a B or Y fare basis, no time restriction. F can be bought by anyone. As the G and I seat inventory reduces, the F will reduce accordingly. The inventory doesn't really change just prior to departure. The airport can upgrade you using the applicable code class for your fare. If there is a seat and you clear the wait list at the airport (based upon the stand-by time at the airport within the tier status i.e. CHP's, Golds, Silvers) you can have the seat regardless of what may have been left in inventory.

Wasn't my post that clear? Same-Same !

Let's take this one step further. With the F4 I3 A2 G1 example what if the seat map shows 6 seats unassigned in FC? I know it is possible to be confirmed in FC and not have a seat assigned. But does this REALLY happen? Isn't it more likely Yield Management's way of blocking 2 seats for whatever reason they choose - oversold coach, flexibility, air marshall, etc...???? What is the real reason behind the difference between the seat map and ITN?

BWI2MCO97
As it happens, while I was typing my response I got called away from the computer and you posted yours. Take a look at the time stamp and then take a prozac.

mileshound
Yes. Yes. Never seen ITN. Strange things also happen with seat maps when the aircraft type may be changing.