It may be largely a matter of personal preference, but there is some evidence that flying westwards causes less jet stress than flying eastwards. Again it is largely a matter of personal preference based on experience. Most travellers think daytime flights cause less jet stress. The dry air in aircraft causes dehydration. Drinking plenty of non-alcoholic fluids counters this.
Water is better than coffee, tea and fruit juices.
Alcohol not only is useless in combating dehydration, but has a markedly greater intoxicating effect when drunk in the rarefied atmosphere of an airliner than it does at ground level. Sleeping aids Blindfolds, ear plugs, neckrests and blow-up pillows are all useful in helping you get quality sleep while flying. Exercise Get as much exercise as you can. Walking up and down the aisle, standing for spells, and doing small twisting and stretching exercises in your seat all help to reduce discomfort, especially swelling of legs and feet. Get off the plane if possible at stopovers, and do some exercises or take a walk.