This was in beginning of 2002 during DL's 2x status miles for YBM fares. I booked an AA ORD-NRT-ORD dep 1/11 rtn on 2/3 for like $450 or so. Got some good onus miles on that flight. Anyway, I had then booked NRT-ATL-ORD-ATL-NRT dep NRT on 1/13, 1/20, 1/27 and returning on 1/19, 1/26, and 2/2. All the DL fares were M so I basically got PLT for $600 x 3 plus the $450 I spent on AA. One of the rtn to NRT the flight was overweight and I took a bump for $700 cash and they gave me the miles for this return. They also let me skip the outbound NRT-ATL-ORD of my next ticket, gave me miles for it as well. They put me on a plane back to ORD in F. Anyway, on my last DL arrival into NRT on 2/2...I got in at like 2pm or so. Since AA was in the other terminal and I thought I had plenty of time for my 6pm ORD departure...I decided to go through regular immigration - not the transit desk. The lady there looked at me like I was nuts. Totally crackers! When asked why I was doing this, all I could think of was to say for FUN. She looked at me strangely but finally let me through. I got to spend a good couple of hours out in the fresh air walkinbg around which was worht it....but I was sure I was soon going to be taken away and strip searched.
In the end I flew 3 roundtrips to NRT in 4 weeks, made PLT with DL, got a total of 135000 miles with DL and 30000 or so with AA. All for about $2000.