Purple. .. .<<does that mean that the centre fuel tank should always be filled first>>. .. .Nice idea - but.... On the big transports the wings are filled first and then the centre tanks(hence why TWA800 had such a small amount of fuel in the centre tank). The fuel is then used in the reverse order of centre, then wing tank. If you have multiple wing tanks you try to burn from centre out to the wing tip. The reason behind this is reduce the bending stresses at the wing root. Fuel in the wing essentially balances out some of the weight in the body. If all the fuel is in the centre and none in the wing, the stresses are at their max and probably result in a payload or other weight restriction. The 767 that I fly can have 10,000Kg in the centre, but you have to have 4,700Kg in each wing tank and you take a hit on the available payload. . . . .<<what happens if an a/c is on standby for long periods in hot weather>>. .. .The solution here is to try and use ground electrics and pre-conditioned air piped from the terminal or jetty. This means you can in theory dispense with the APU and the air conditioning packs. The performance of some pre-conditioned air systems does though leave much to be desired and are availble (usually for airport noise reasons) at only a few places.. .. .Also TWA800 was ready to go and was awaiting some bags, this probably means that had they been using such a system, they would already have removed it.. .. .Nobody said it was going to be easy.....