CNN recently came up with advice on how to survive a plane crash.  Make a plan, brace yourself, know where the exits are, and so on. All good stuff.  But if you really want to increase the odds of surviving your flight, here’s what you need to do: every hour, unbuckle your seatbelt, get up, and walk around for 5 minutes.  Then drink a glass of water.

The biggest threat to your health and safety on board a long-haul flight is not a crash.  It’s something called "Deep Vein Thrombosis."  In plain english — blood clots.  The clots are relatively harmless if they stay in your legs where they first develop.  But if they break off and move through your system, they can cause fatal pulmonary embolisms, strokes, or heart attacks. Walking around during your flight and staying hydrated are among the best ways to keep clots from forming.

The risk of death from blood clots dwarfs all other aviation-related risks. An airline traveler is 100 times more likely to die from an airline-induced blood clot, for example, than from all causes related to bad weather, pilot error, mechanical failure, and terrorism combined. estimates that up to 100,000 people die each year as a result of airline induced DVT.  On the other hand, less than 1000 die each year from airliners going down. 

The airlines have been aware of the risks of blood clots since the 70’s. Nonetheless, the airlines have done little to spread the word. In fact, they’ve kind of kept the risks under wraps.  We don’t expect that to change, since the courts have ruled repeatedly that the airlines have no legal obligation to warn their passengers about the risks of DVT and what can be done to avoid them

What factors contribute to formation of blood clots? Stasis — the pooling of blood in the legs from prolonged sitting; decreased blood oxygen levels resulting from the cabin environment, bruising of deep vein in the back of the leg from prolonged term sitting (no, you can’t feel it happening) , and dehydration that results from the dry cabin air.

Walking around every hour or so and remaining hydrated are good strategies for avoiding Deep Vein Thrombosis and staying safe.