If it is A0 F0 Y9 H9 K9 B9 then you will not be able to buy a first class ticket no matter how much you are willing to pay. But in my experience, some funky things happen to the A bucket as flight time approaches.

Last Thursday I was contemplating a change from my 3:55pm departure for EWR from LAX to the 12:45pm but when I checked at 10am and again at 10:45am there were no A seats available (I was on a full Y fare and did not want to move to the earlier flight if it meant sitting in the back).
I had resigned myself to taking the later flight but then thought I'd check the fare buckets throughout the 2 hour pre-flight window for kicks to see if things shifted around at all. Since I am 38 miles from LAX once 10:45am passed, I figured that the earlier flight was no longer an option so I did my on-line check in (I was already in first for the late flight but like to use on-line check-in since I sometimes cut it a little close to the 30 minute cut-off for front of airport check-in). Well sure enough at 11am the flight shows A1! So strange things do happen!

To finish my story...
I looked the traffic report website and it showed clear sailing to LAX from Burbank so I rolled the dice and called the Platinum desk. They put me on hold for 10 minutes as they had to "check me out" of the 3:55 flight. They came back on and I was now in a panic as I had about 1 and a half hours to drive 38 miles, return a car, shuttle to Terminal 6 (w/4 stops at terms 1-5), clear security and get to the gate before it closed (and since I gave up my F seat on the 3:55pm, I may have to sit in the back as that now showed A0). So I took about 1 minute to try to check-in on line for the earlier flight after the agent assured me that I could- but it didn't work. So I shut down my laptop and ran out the door at 11:20am. After all my speedy driving and good rental car process, I walked through the door of terminal 6 at 12:20pm. Luckily I saved my printed out boarding pass from the 3:55pm flight (so no worries about the 30 minute rule), breezed through security and had a Heineken in my hand in 3A by 12:32pm (and lots of sweat on my brow). I have to start taking a more relaxed pace!!!