mach92:

What flights are you booking? I kept getting errors on AA.com, but I got 4 fares from $471-$480 on Orbitz (leaving DFW on a Saturday and returning Sunday). The problem is that all of these turnarounds have less than 3 hours between arriving and departing NRT. I called AA and the agent said that it's not nearly enough time to clear customs and get checked in for the return flight.

With the prices in Tokyo, having to stay there one night makes CFM3RD's run to LHR look a lot more attractive.

She also said that on an international turnaround, be prepared for questions from security - I think everyone takes this as a given.