If they would just cut back on 1 JFK-LAX frequency and use that plane on MIA-LAX I'm sure many would appreciate it
But why on earth would AA do that? JFK-LAX is an exceptionally competitive route where both frequency and product matter tremendously in attracting high-yielding business traffic. MIA-LAX, by contrast, is a route where AA is utterly dominant and faces minimal competition in terms of both frequency and product. So why would AA pull a very low density, very premium aircraft off of the former to put it on the latter?
AA is working on a plan to start using the lie flat 757s transcon (not just on MIALAX).
I sincerely hope that's true.
With AA's international 757 flying continuing to decline, the natural place to put some of those planes is on competitive transcons. I would love to see AA doing 3x daily JY 757s on BOS-LAX and 2x daily on each of JFK-SEA, JFK-SAN, DCA-LAX and yes (beating a dead horse) BOS-SFO. All of that would account for the utilization of less than half of AA's JY 757 fleet that, otherwise, is only really going to be needed at this point for, essentially, a smattering of routes to Europe and South America that can easily be operated with the remainder of the JY-configured 757 fleet not doing transcons.
All that said - I'll very much believe it when I see it.