Deep vein thrombosis (DVT) occurs when blood clots form in the legs during plane fights, chiefly because of prolonged immobility. The longer the flight, the greater the risk. Though most blood clots are reabsorbed uneventfully, some may break off id travel through the blood vessels to the lungs, where they may cause life-threatening implications.
The chief symptom of 6VT is swelling i pain of the foot, ankle, or calf, usually i just one side. When a blood clot travels i the lungs, it may cause chest pain and difficulty in breathing. Travellers with any of these symptoms should immediately seek medical attention.
To prevent the development of DVT on long flights you should walk about the cabin, perform isometric compressions of the leg muscles (ie contract the leg muscles while sitting), drink plenty of fluids, and avoid alcohol and tobacco.

JET LAG & MOTION SICKNESS

Jet lag is experienced when a person travels by air across more than three time zones (each time zone usually represents a one-hour time difference). It occurs because many of the functions of the human body (such as temperature, pulse rate and empty-ing of the bladder and bowels) are regulated by internal 24-hour cycles. When we travel long distances rapidly, our bodies take time to adjust to the 'new time' of our destination, and we may experience fatigue, disorientation, insomnia, anxiety, impaired concentra¬tion and loss of appetite. These effects will usually be gone within three days of arrival, but to minimise the impact of jet lag:
Rest for a couple of days prior to date of departure.
Try to select flight schedules that minimise sleep deprivation: arriving late in the day means you can go to sleep soon after you arrive. For very long flights, try to organise a stopover.
Avoid excessive eating (which bloats the stomach) and alcohol intake (which causes dehydration) during the flight. Instead, drink plenty of noncarbonated, nonalcoholic drinks such as fruit juice or water.
Avoid smoking during the journey.
 Make yourself comfortable by wearing loose-fitting clothes and perhaps bringing an eye mask and earplugs to help you sleep.
On the flight, try to sleep at the appropri¬ate time for the time zone you are travelling to.

Eating lightly before and during a trip will reduce the chances of motion sickness. If you are prone to motion sickness, try to find a place that minimises movement -near the wing on aircraft, close to midships on boats, near the centre on buses. Fresh air usually helps; reading and cigarette smoke don't. Commercial motion-sickness prepar-ations, which can cause drowsiness, have to be taken before the trip commences. Ginger (available in capsule form) and peppermint (including mint-flavoured sweets) are natural preventatives of motion sickness.