Jet lag is caused by a complex combination of circumstances. First, the environmental deviations of traveling - time changes, alterations in magnetic fields, climate differences, and diverse cultures all can deplete energy before settling in at our destination. Flying in commercial jets exposes our body to an unhealthy environment where we are deprived of air and humidity, with heightened exposure to radiation, pollution, and chemicals such as pesticides and cleaning solutions. 

Before flying 

• Pack light and try to limit luggage to a carry-on, since most airline baggage compartments are regularly sprayed with pesticides, which in turn contaminate checked baggage.
• Wear layers which lessens your baggage weight and also allows you to be comfortable if temperatures fluctuate in the cabin. 
• Avoid alcohol, coffee, and tea before flying, and substitute lots of water instead. This will help offset dehydration, and promote mental clarity. 
• Rest beforehand. Give your body a head-start adjusting to the time of your destination by varying your sleep patterns. To help re-set your biological cycles, set your watch to the local time at your arrival destination when you first board your flight. Sleep on board if your flight lands in the morning and avoid sleeping on board if your flight lands in the evening.  

Fast or bring your own snacks

Travelers experience less jet lag when they skip all airplane food. It's typically high in fat, salt, and sugar, which is harder to digest in the low air pressure found in the cabin. Try fasting from solids and foods, only drinking water for the duration of the flight. If fasting is difficult, bring along healthy alternatives such as fresh fruit, or carbohydrate-rich snack bars in your carry-on.   

Fighting air quality

The in-flight air is drier than any of the world's deserts. Relative humidity is typically 20-25% in the Sahara or Arabian deserts, while optimum comfort is around 50%. In-flight dryness can create thirst, scratchy and bloodshot eyes, dry skin (even wrinkles), constipation and thicken blood which could lead to blood clots. Air also becomes increasingly stale as it is recycled throughout the flight. Some simple steps to minimize the effects of in-flight air quality: 

• Drink water - at least 8 ounces of bottled or packaged water every hour en route. Avoid tap water because the cleanliness of commercial aircraft water tanks could be unhealthy. Carry your own bottle of drinking water to sip when service is not available.  
• Avoid alcohol and coffee since they have diuretic properties, which squeeze water from our cells.  
• Spritz your face often. Use an empty perfume atomizer and refill it from your own drinking water, or buy a water spritzer to keep your skin fresh and hydrated.  
• Moisturize. Apply eye cream below eyes, and oil inside your nostrils (almond oil, jojoba oil, or olive oil are recommended).  
• Humidify the air you breathe by covering your nose with a water-saturated cotton handkerchief. (Fold on the diagonal and wrap ends around your ears.)
• Suck on zinc and vitamin C lozenges, which help keep bugs at bay. Dry mucous membranes are more susceptible to bugs, so these with plenty of water will help protect you from falling ill.
• Cleaner cabin air. To purify the contagion-filled cabin air use a personal air ionizer that can be worn around your neck. 

In-flight exercises

Long flights can cause swelling and put you at risk for developing dangerous blood clots in your heart, lungs, or brain. Walk around the cabin frequently, and stretch with these exercises that can easily be done in your seat.

• Sit with your feet flat, hip-width apart. Lift your heels so that only the balls of your feet are on the floor. Hold for five to 10 seconds. Lower your heels. Repeat 10 times.
• Sit with your feet flat, hip-width apart. This time lift the balls of your feet so that only your heels are on the floor. Hold for five to 10 seconds and then lower your feet. Repeat 10 times.
• Stretch your legs out under the seat in front of you. Raise your straightened right leg slightly, and rotate your foot clockwise at the ankle 15 times and then rotate your foot counterclockwise 15 times. Repeat with your left leg.

After arrival

There's no way to avoid the fact that your body will become tired and dehydrated to some degree as a result of flying. Some things you can do after landing to recover from your travels:

• Bathe. Submerge and soak in water as soon as possible - the ocean, a hot tub, a pool, a bath. Immerse entirely, especially your head. Bathing when dehydrated helps replenish moisture through the pores, while relaxing the nervous system.
• Drink plenty of pure water for several days after landing. Without adequate water intake both health and inspiration quickly deteriorate. 
• Plan activities wisely. When you first arrive, schedule work or other important activities at a time when you are likely to have maximum energy, (i.e., in the evenings, after flying east, or in the mornings, after flying west).
• Get some natural light. To help speed up acclimatization, spend some time outdoors every day during daylight hours. Even being in a room with windows helps energize your body and reset your internal clock.

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