Thanks for the tip, moondog. I checked it out and yes, MU flies in both directions between NKG and NRT once on Sundays and once on Thursdays. The flight is sold both as MU and as a JL codeshare. In the NRT-NKG direction, however, the flight departs before any of the AA flights land at NRT, so that would still indicate an overnight layover when arriving at NRT from the US.

Also, the best route, as you also mentioned, would be on LH: BOS-FRA-NKG. Very easy. I'll suggest it but I believe my colleague wants to stick to AA as much as possible.

I wonder if it's easier to overnight at the NRT Hilton or the PEK Hilton…

jiejie, I appreciate the information about trains. I will pass that on as well!