Air travelers are often warned to move about during flights to lower their risk of forming blood clots, and some airlines have even created in flight exercise plans to encourage frequent movement. But what is your actual risk of developing this dangerous condition? Dutch researchers have actually nailed the number down, and the average person's risk might be less than you think: 1 in 4,656. Some people who don't fall into the "average" person category are:

• people under 30
• women on birth control pills
• those who are overly short, tall, or overweight

In addition, your risk doesn't drop the minute you walk off a flight. Instead, it lasts up to two weeks. So while you may not be at a high risk for developing a blood clot during travel, all the moving around still can't hurt.