It can happen when the blood does not move through the vessels adequately, for example, after sitting through long flights.
Symptoms can appear several weeks after flights as short as three hours.
Such clots have been reported after automobile trips and even after evenings at the theatre, but long flights seem to pose a greater risk. The syndrome can result in anything from minor body pains and shortness of breath, to heart attacks and strokes. A young English woman who died after a long return flight from the Sydney Olympics put the risk of deep vein thrombosis in the headlines. However, it should be noted that this problem is not new and has been evident for many years. It has come to prominence recently with the ever-increasing number of air travellers.