I'd say a very optimized DONE3 ex-TYO or ex-OSL, but I'm certainly not going to check the various earnings tables for economy flights to see if it could be done cheaper that way. Not a chance in h*#l I'd do that again, I stopped that in my UA days when they stopped crediting 1 mile flown for 1 status mile. These days premium cabins are the way to go when optimized for status earning.

But from what I've learned from this forum, AA is not the program to do it on unless you're already EXP with them. AS, AY, and perhaps QR depending on your flying patterns seem to be the easiest ones, but again that's premium cabin only. I can't be bothered to check the easiest way in economy. Too many OW carriers credit economy at 25% and I have zero desire to attempt that ever again.