Venous thromboembolism has been associated with long-haul air travel, but whether this is due to the effects of prolonged sitting or other factors, such as reduced oxygen tension in the cabin, is not known. To assess the effects of hypoxia on markers of activated hemostasis during simulated long-haul air travel, Toff and colleaguesArticle conducted a single-blind, crossover study performed in a hypobaric chamber. Healthy study participants at low risk of thrombosis were seated for 8 hours in the chamber and exposed to hypobaric hypoxia or normobaric normoxia, equivalent to commercial air travel or atmospheric conditions at ground level, respectively. Blood samples were taken before and after chamber exposure to assess changes in markers of hemostasis. In analyses of pooled data from the study participants, the authors found no evidence of procoagulant changes that could be attributed to hypobaric hypoxia. In an editorial, BärtschArticle discusses the clinical implications of data from studies of hypoxia and inactivity and their effects on coagulation.