Here are the facts about clots and how to prevent them. A deep vein thrombosis occurs when blood clots in the deep veins of the legs. A clot that passes up the blood vessels and through the heart can become lodged in one of the small blood vessels supplying the lungs. The result is that this can cut off the oxygen supply to the body. This potentially fatal condition is known as a pulmonary embolism.
Some people have a higher than normal risk of deep vein thrombosis.
These people are those most at risk of blood clots when they fly. Staying still for longer periods, such as when in an aircraft seat, slows blood flow from the legs back to the heart, which increases the danger of blood clots. Restricted leg-room can slow the flow of blood even more, particularly when the back of the seat in front is pressing on the front of the legs. It is not clear by how much flying increases the risk of deep vein thrombosis, because there has been little research. Last year a Government-commissioned report estimated the risk was 'exceedingly small' for healthy people.