Flight socks being used for the prevention of deep vein thrombosis (DVT) on a long haul flight. Deep vein thrombosis is a condition in which a blood clot forms in a deep vein in the leg. The clot may later detach and move to other areas of the body, such as the heart, lungs and brain, which can be fatal. The condition is linked to long periods of inactivity, dehydration, cramped conditions and low pressure (such as that found in an aircraft cabin). The socks help prevent DVT by supporting the leg veins, aiding normal circulation. It is also suggested that passengers on a long flight exercise their legs regularly, walk around the cabin, and drink plenty of water.