Thanks for the good advice. I had imagined that the whole lot of M seats were blocked by travel agents keen on selling packages, and that the unsold seats would be cheaply released as the date approaches.

Actually I am doing ORD-NRT-SIN arriving NRT on AA and need to fly AA7215 NRT-SIN, but as that seems hopeless I looked at JL711 which has M0 for most of December and early January. Strange thing is the morning and afternoon flights NRT-SIN are all widely available. The best I managed was to arrive in the early evening on day X and depart mid-morning of (X+1) on any one of numerous JL flights showing M7.