Some of the most common symptoms of Jet Lag are:

• Fatigue
• Decreased awareness and motivation
• Disrupted sleep after travel
• Dehydration
• Discomfort of legs and feet
• Irritability
• Headaches

What Causes Jet Lag?
The greatest cause of jet lag is rapid transit across world time zones. The more time zones we cross, the greater the disruption of our body clock (a small cluster of brain cell which governs our temperature, heartbeat, blood pressure, and physiological patterns - circadian rhythms), resulting in disorientation and mental and physical fatigue.

Sitting still for long periods of time in flight causes discomfort and possible swelling of the legs and feet (see "Deep Vein Thrombosis"). The dry atmosphere in airliner cabins can cause body dehydration. Altitude and pressure changes at each landing and takeoff also upset body systems, and although airliner cabins are pressurized, these changes are significant causes of jet lag. Lack of fresh air, aircraft noise and cramped cabins also have a role in the process.

What Can Be Done?
Start Rested
The preparation for a long trip often means you're tired before you begin. If at all possible, get enough rest in the days prior to your trip, so you can start out strong and full of energy.

Sleep During the Flight
It's best if you can sleep on the plane. Kick your shoes off. Earplugs, eyeshades, and a comfortable neck pillow are well worth the effort of packing if they prevent you from losing a day to jet lag. Try to take care of as many travel details as possible before you leave so that flight day is stress and anxiety-free, and wear comfortable clothes and shoes. Set your watch to the destination time as soon as you board the plane.

Many travelers have depended successfully on Jet Lag pills to help them feel fresh on arrival (eg Melatonin). While a drink or two may relax you, alcohol can dehydrate you, making your symptoms worse. Avoid sleeping pills and mind-altering pharmaceuticals on the day you fly. In the event of an emergency, you will need all your faculties in order to survive.

Drink Water
The dry air in aircraft causes dehydration. Plan on drinking 1/4 to 1/2 litre of water during each hour of travel. Resist caffeinated and sugared drinks, which can actually make you more dehydrated. Have a nice, long hot bath when you arrive to rehydrate and relax.

Exercise
The long periods of sitting on an airplane, bus, or train are hard on your body. Walking and stretching exercises in flight will help your body adjust to the new climate. To help reset your body clock, try to stay awake until bedtime rather than taking a nap upon arrival - spending time outdoors seems to help most travelers.

Showers
During extended stopovers a shower not only freshens you up but also gets the muscles and circulation get going again and make you feel much better for the rest of the flight

Experience
As you travel, experiment to find the system that works best for you. Some travelers forswear all naps, others insist on them. Keeping note of your experiences will help you get the most from future trips. Consult with fellow travelers, too. Their experiences can help you avoid days lost to jet lag discomfort

East and West
The issue is under debate, but there is some evidence that traveling westwards causes less jet lag than traveling eastwards. Remember this for round the world trips.