Thank you for the replies. My plan is to use lit-lhr AA, lhr-ath BA, sin-nrt JAL, nrt-lit AA. The return route is to minimize travel time, but the seats are not guarantied until I am able to book in a few weeks.
I was trying to come up with a plan to be able to upgrade to first with the miles I have. (Can't come up with the miles for first on the OW award, but have enough for the all-partner in first)