Three recent case-control studies provide conflicting results on the possible association between air travel and venous thromboembolic disease. A report by Ferrari, et al, shown here, suggests a higher percentage of air and train travel among persons with DVT and emboli (cases) and those without it (controls).

See: Ferrari E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk factor for venous thromboembolic disease; a case-control study. Chest 115(2):440-444, 1999.