Drink plenty of water before and during your flight. Purchase water upon getting to your gate or ask for some when beverages are offered. High altitudes can trigger dehydration, which can cause your body to feel tired and decrease blood flow.
Use light to help regulate your body to you destination's time zone. Change your watch to your destination's time zone. Then turn on your overhead light and try to stay up during daytime hours of your destination. Bring dark glasses or eye covers and create a dark environment during the evening hours at your destination.
Regulate your food intake to coincide with meal times at your destination. Many airlines serve food based on destination meal times, but you can bring your own food to ensure you are able to get your body accustomed to eating during your destination's meal times.
Move on the plane. Exercising and stretching increases blood flow and reduces muscle stiffness. An isometric exercise book provides examples of in-seat exercises.
