again, unless I dreamt this, I am sure the days of Y-up fares are over. They used to be called "instant upgrade" on the website and AA had fiddled it so it was a Y fare / class that 'instantly' upgraded to a premium cabin.

I dont think they do that anymore and P is just another F fare bucket these days.

I'd personally still call BA / AA and try to get on a flight that gives a bit of breathing space. yes, Calchas is right (of course!) that there are frequent LAX - JFK but that doesnt guarantee you a seat etc. And I prefer having a sit, cup of tea, glass of water and ideally a shower in the LAX lounge (which is decent for all that) before another long flight rather than running to the next flight....