Originally Posted by opalfruit

21C is indeed the correct temperature for waking activity - workers in office buildings and the like, and fine for daytime activity on aeroplanes, but it is too warm for sleeping. It's true, of course, that not all regions of the world have uniform temperatures, and people will adjust and acclimatise to their locality over time - but it still doesn't mean that it is optimal for you or your body. People who live in very warm climates often do not utilise bedclothes or sheets or blankets as there's no need for them, and they may find 18C to be chilly - and that's *exactly* what blankets and pillows are there for. If you are still uncomfortably cold, when under a blanket, with all your clothes on, when the ambient temperature is 18C, then - frankly - something is wrong with you.

Most modern aircraft have the ability to selectively cool or heat zones of the plane, so passengers in Y can be kept a few degrees warmer than those cosseted in J and F. You're right that not everyone will want to sleep during a night flight, and some people will want to sleep on day flight, but the airline should cater generally to the majority of the passengers, not to outliers. Keep it warmer (21C) on day flights, and keep it cooler (19C-18C) on night flights. Ensure each passenger has a blanket if they require one, I'm reasonably sure BA manage to do this even in Y. Passenger comfort would be significantly improved.

FWIW, never had a problem with JAL - though I've only flown with them perhaps 10 times, and mostly longhaul in J/F.