Many people who travel, whether they are used to traveling or not, suffer from jet lag due to the time differences in different countries.
Start adjusting your body even before your flight. This means trying to move up or down an hour your usual schedule for about a week before your day of departure. Maintain this even while you’re on the plane.
Keep yourself hydrated and properly nourished. Do not overindulge in caffeine and get yourself well-rested. Keep yourself moisturized too so you feel better even with bad cabin conditions.
Once you’ve landed, try to stay awake during the day and get much sleep at night. Exercise if you can as this will keep your body slowly get in tune with its surroundings.
If after a few days and you haven’t got any decent sleep, consult a doctor.