This could be due to jet-lag disorder, this is a temporary sleep problem that can affect anyone who quickly travels across multiple time zones. Your body has its own internal clock, or circadian rhythms, that signals your body when to stay awake and when to sleep. This disorder occurs when your body's clock syncs with the original time zone. You will find it more difficult when you fly eastwards, crossing number of time zones etc. Drink plenty of water, fluids (stay hydrated) before, during and even after the travel. Consult your General Physician for some mild medication.