Is it just me or does ITA seem to be much twitchier lately about returning all/best results if you ask for too many options of departure airport/connection points, etc.? I wonder if they lowered the search timeout.
So these may or may not show up reliably, plus there were some Monday departures that show as much higher on the flexible calendar but drop into the $750-$760 range if you click on an individual day. Some involve an extra connection). If you have specific dates you're interested in I'd poke around just to see what happens.
Got a couple of these to checkout page at DL via the ITA userscript but did not actually try to purchase, YMMV.
Samples:
SFO-DTW/JFK-NRT-SIN-NRT-DTW/JFK-SFO 24,463 MQMs
Apr 11-14 $758 ai 3.10cpm
Apr 18-21 $758 ai 3.10cpm
SFO-DTW-NRT-SIN-NRT-DTW-SFO 23,608 MQMs
Apr 18-21 $753 ai 3.19cpm
May 23-26 $753 ai 3.19cpm
EDIT: BTW the 2-for-1 Gogo global pass is now good thru March 31:
http://www.gogoair.com/delta-global-day-pass