LONG TRAVEL INCREASES CHANCE OF BLOOD CLOTTING

USA Today - The risk of venous thromboembolism, a rare but potentially deadly clot-forming condition, is three times greater for travelers than for people who are not cramped for many hours in airplanes or on other forms of transportation, says one of the first studies to measure the risk.

The report in the Annals of Internal Medicine warns travelers about the importance of knowing the symptoms and staying hydrated and mobile to help prevent the condition from developing during long trips. . .
The study also found an 18% higher risk for each two-hour increase in duration of travel "by any mode" and a 26% higher risk for every two hours of air travel.

One remedy would be for airlines to provide adequate leg room - TPR