Prolonged air travel can lead to a DVT (a blood clot in the deep veins, usually in the lower legs). Part of the clot can break off and travel to the lungs (a pulmonary embolus), which can be fatal.

Below-knee elastic compression stockings or 'flight socks' (available at pharmacies) improve the circulation in the legs and greatly reduce the risk of developing a DVT while flying. They are especially useful for people at higher risk, such as those with a previous DVT or women on the Pill.