A product that combines Nattokinase and Pycnogenol (Flite tabs) was shown to completely prevent a type of dangerous blood clot called a deep venous thrombosis (DVT). In the study, none of the group taking the Flite Tabs had DVT’s, but 5 % of the control group did. Since DVT’s can be life threatening this is very significant. You should consider taking Flite Tabs on any flight over 2 hours. Remember to do various leg exercises during the flight as well.
 
The other option is to take Nattokinase and Pycnogenol separately, but the exact dosages are not disclosed by the company that makes the product.
 
Angiology. 2003 Sep-Oct;54(5):531-9. Prevention of venous thrombosis in long-haul flights with Flite Tabs: the LONFLIT-FLITE randomized, controlled trial.
Cesarone MR, et al.