Most travellers become more jet-lagged flying east than they do flyng west. Flying east, the day shortens; it is hard to stay asleep, and one is tired in the morning. Flying west, the day lengthens, so one wakes too early and is sleepy in the evenings.
The disorientation creates a special difficulty for international diplomatic and business missions since the travelling party is at a disadvantage in any meeting following arrival. There is also some evidence that suggests the existence of cumulative long-term effects which shorten the life span in the case of frequent travel of this kind.
Jet lag, which is partly sleep deprivation and partly bodily confusion, causes efficiency problems for transnational corporations and military organizations which need to be assured that their representatives (businessmen, soldiers) are fully alert after a long journey across time zones. Airline pilots spending a week or longer on international flight schedules with long hours and multiple crossings of time zones have difficulty staying awake while flying and sleeping during layovers. For holiday travellers, the reorientation period inconveniently cuts into their allotted vacation time.