I was not saying a hard and fast rule .. just an observation for lots of flights in the past. If there are 4 seats (20% of MD80) unassigned before the 100 hours .. then I presume it will be gate upgrade (no EXPs or lower getting upgraded at their normal tier time frame) ...

Last week I was on a 757 with 2 unassigned seats at the under 100 hour mark (my upgrade did not clear) and on the day of the trip my originating ticket counter rep told me that the flight was totally full in First and I would have to standby for a last minute upgrade. [Luckily the flight before this had confirmable upgrade and the AAgent switched me to that flight.]

As far as the 'dumping' at nn hours .. AA in my past experience has always held a few seats for gate assignment/last minute full fare purchase.

Most of my travels are mid-con (vs trans-con) so there may be differences there also ... and I presume DFW vs ORD might have different YM 'formulas' on specific flights. My post was just wondering why this 'rule' that has seemed to work for so long (and continues to work on other flights the same day) is not working on this specific flight....

I also would NOT trust your profile to force aisle seats ... there seems to be a glitch someplace where AA.com changes your preference on you randomly. I too am an aisle seat person. Yet twice in the past 2 weeks I was assigned window seats .. then looking at my profile find yes that is what is listed there. I change it back to aisle and in a week it magically changes back to window.....

Just another confusing part of AA!