How to Avoid Blood Clots on Long Plane Rides

Where You Sit Matters

Longer plane rides lead to a higher risk for blood clots.
Longer plane rides lead to a higher risk for blood clots.. Erik Isakson/Getty Images

Did you know that long plane rides could increase your risk for a blood clot? The longer the flight, the greater your chance of a deep venous thrombosis, or blood clot in a deep leg vein. Here's what you should know about why this occurs and what you can do to protect yourself — including what seat to choose to lower your risk.

Who Is at Risk?

The greatest risk is for passengers on flights that are over four hours in length.

If a clot breaks off and travels to the lungs in the days or weeks following a trip, it can form a potentially life-threatening pulmonary embolism.

There are many risk factors for developing a deep venous thrombosis, such as being over the age of 40, obesity, a genetic predisposition, a previous deep vein clot, and hormone use. But research has also found that your seat choice on a flight can also play a role.

It turns out that sitting in a window seat increases the likelihood that you'll develop a deep vein clot, when compared with sitting in an aisle seat, according to researchers in the Netherlands. Obese passengers who sit in a window seat are at a much greater risk of a clot: up to six times higher when compared with passengers of regular weight in an aisle seat.

The same researchers found that passengers who sit in business class have a slightly lower risk of developing deep vein thrombosis when compared with passengers flying in economy.

This could be because window seats tend to be more cramped than aisle seats, especially for obese passengers. An aisle seat may also allow you to get up and move around more easily than you can when seated by the window.

Avoid Deep Vein Thrombosis

Luckily, you can take steps to avoid deep vein thrombosis when you travel.

If you're over the age of 40, pregnant or taking hormone therapy or have a prior history of deep vein clots, the Centers for Disease Control and Prevention (CDC) recommends choosing an aisle seat when feasible, and doing calf muscle exercises, such as stretching and flexing your calves, while seated. Frequently walking up and down the aisles during the flight can increase circulation and help prevent clots. Compression knee socks are also recommended for this high-risk group. Staying hydrated may help, but there is a lack of evidence showing that dehydration is linked to travel-related deep vein thrombosis.

For more information about air travel and medical emergencies, take a look at these resources:

Avoid an In-Flight Emergency​

In-Flight Medical Emergencies for Older Travelers


Nimia Reyes, Scott Grosse, Althea Grant. "Travelers' Health: Deep Vein Thrombosis and Pulmonary Embolism." US Centers for Disease Control and Prevention Public Information Sheet. Accessed July 23, 2014.

Partsch, Hugo, Beatrix Schobersberger, and Wolfgang Schobersberger. "Travel-related Thromboembolism: Mechanisms and Avoidance." Expert Review of Cardiovascular Therapy 7.12 (2009): 1559.

Schreijer AJM, Cannegieter SC, Doggen CJM, Rosendaal FR. The Effect of Flight-related Behaviour on the Risk of Venous Thrombosis After Air Travel. Br. J. Haematol. 144, 425-429 (2008).

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