Originally Posted by moondog

Since that breaks the "single partner" rule, and DFW-SIN is a LONG flight (2+ partner awards are distance based, as you know from your own research), I'm afraid that Happy's advice is spot on. However, since AA flies DFW-NRT nonstop, I'd be tempted to grab that and use UA miles for NRT-SIN (currently 30k miles RT in C or 20k in Y).

ETA: It might be possible to score a JL flight number on DFW-NRT. I know code shares aren't supposed to work, but since PDX-LAX does, this would be worthy of further investigation.