Seeing the signs Economy class syndrome affects one in 100,000 passengers on long-haul flights, but the number who die is only a small fraction of the figure. When sitting for long-periods blood clots form in the legs and can, if dislodged, travel to the heart or lungs and can cause death. Passengers on flights of more than six hours are most at risk. Those who are pregnant, on the contraceptive pill, smoke, have varicose veins, suffer blood disorders or have recently had an operation. Dehydration - drink plenty of water and avoid alcohol.
Some doctors recommend aspirin before and during the flight as it thins the blood.
Support stockings, like those worn by patients undergoing surgery, are a useful preventive for higher risk groups.