Some experts recommend against airline travel during the first 4 weeks following deep vein thrombosis (DVT) or pulmonary embolism (PE). However, there is little scientific evidence to support this guidance. Some data have indicated that the hypobaric (low pressure) condition in the airline cabin activates our clotting mechanism and that that is one of the reasons why people who fly long-distance have an increased risk for developing DVT and PE. However, whether that is truly of clinical relevance is not known.
Since it is not fully known whether airline travel in the first few weeks after an acute DVT or PE is truly detrimental and should really be avoided, the recommendation to avoid air travel is more a cautious suggestion rather than a firm avoidance.