However, anyone traveling more than four hours, whether by air, car, bus, or train, can be at risk for blood clots.

Yes, a 5-hour flight can technically cause a blood clot, known as Deep Vein Thrombosis (DVT), although the risk is much lower than on "long-haul" flights of 8 hours or more. The risk arises from prolonged immobility in a cramped seating position, which causes blood to pool in the lower legs. In 2026, medical consensus suggests that about 1 in 6,000 passengers on flights over four hours may develop a clot. The risk factors are cumulative: if you are over 60, use oral contraceptives, are pregnant, or have a history of heart disease, even a 5-hour journey warrants caution. To prevent this, doctors recommend performing "calf raises" while seated, staying hydrated (water, not alcohol), and walking the aisle at least once mid-flight. While rare for healthy individuals, the "cabin pressure" and "dehydration" of a 5-hour flight can trigger a "coagulation cascade," making it essential to move your legs frequently to keep blood circulating toward your heart.