You’re traveling from Chicago to Honolulu, crammed in economy class—where the seats are tight, and you’re just an inch from being really intimate with the stranger sitting next to you. Thankfully he smells nice, and looks fit. He looks like he’s probably on his way to the Ironman Triathlon. You can feel the warmth emanating from his trim body.

Wait… where was I? Oh, yes…

So you’ve spent eight hours crossing the Plains and over the Pacific Ocean. You finally land in Hawaii. You’ve settled into your hotel room, and then it begins: shortness of breath, chest pain, sweating and dizziness. Your skin is getting clammy and you’re turning an awful shade.

What could have gone wrong?

This situation is scary and has actually affected hundreds each year who travel on long-haul flights—flights lasting more than four hours. A Dutch research team found that 1 out of 4,500 people who fly will end up with a scary scenario similar to this, within eight weeks from traveling.

A blood clot has formed over the course of sitting idle on an airplane for hours. It has broken off and traveled from the legs to the lungs, causing a blockage.

It’s called venous thromboembolism (VTE)—a combination of deep vein thrombosis (DVT) and a pulmonary embolism (PE). The grim fact is that you can die from it—if not treated as soon as signs and symptoms manifest themselves.

But there are ways to protect yourself from getting the blood clot that causes this nightmare scenario.

My first tip is to talk with your doctor if you’re expecting to make a long-haul flight, or even train, bus, or car ride. Your doctor can discuss the blood clot risk factors particular to you, and make recommendations to help you get through your travels safely. Follow your doctor’s advice.

The most important tip is to move around. Every now and then, unbuckle your seatbelt, get up, and walk about the cabin for a little bit. The goal is to get blood moving through your legs and arms. It actually shouldn’t take long to do this.

There are sitting exercises you can do to help improve blood flow and reduce your risk for blood clots. Here’s a simple exercise set that you can do during your flight:

  • Extend your legs out in front of you, as far as you can get them, several times.
  • With legs extended, point your toes, and flex your ankles up towards you, several times.
  • Rotate your ankles to the left several times, to the right several times.
  • Lift your knees up and down, several times.
  • With heels flat on the cabin floor, raise your toes up and down.
  • With toes flat on the cabin floor, raise your heels up and down.
  • Pull your knees up towards your chest and hold it. Do this ten times for each knee.
  • Breathe deeply, in and out. This sends oxygen flowing.

While the risk of developing blood clots increases if a person is overweight or have certain medical conditions, even the healthiest of people have developed VTE. Also, don’t think that business and first class passengers are immune from blood clots. It’s happened to them, too.

In the end, avoiding blood clots is a matter of being vigilant about not being idle too long, and keeping the legs moving. If you do this, you should be fine.