cattleclass: Having just flown a 12 hour all daylight flight with SQ318
FWIW, my take on it is this. The flight may happen to be in physical daylight, but that's not the only consideration. Even if it was the only sector I was flying, I would have had to get up pretty early in SIN to get on it. The flight arrives in London at 2330 (body clock time), but it would still take some time before getting to my final destination. That, of course, may be the office. So having a dark cabin for some sleep during the flight would be lovely.