Headline-making tragedies may worry anxious fliers but common issues, like flight lengths and common germs, pose some of the greatest risk to travelers.

While simply boarding a plane won't guarantee you'll get sick, professor Ron Eccles, director of the Common Cold Centre in the U.K., says that the more time people spend cooped up in a confined space like an airplane cabin, the more likely they'll contract an airborne illness.

“We get colds when we are flying because we there are three or four hundred people all squeezed in together in a small space,” Eccles told the Daily Mail. “You can guarantee that some of those people will have colds and the germs are spread because of crowding.”

Flying also leaves you dehydrated. Combine that with a lowered immune system due to the stress of traveling, and it can leave travelers “more prone to the cold virus.” 

“The virus is most likely to be spread by touching infected surfaces on the aircraft like the seats and the toilets. We pick up colds because of proximity to people who have them and the length of the exposure," Eccles said.

Someone traveling from New York to Miami—about a three hour flight—will usually fare better than someone jetting farther afield like to the Mediterranean or Asia. Long flights also increase the risk of potentially lethal blood clots also known as Deep Vein Thrombosis (DVT), according to former commercial pilot Tom Bunn, who helps nervous fliers overcome their fears.

"One study shows that frequent fliers are 3.65 times more likely to develop DVT than non-fliers,” Bunn told the website Supercompressor. “A non-profit DVT organization reports that three to five percent of air travelers will develop clots. Yet, it is unclear how big a role flying plays in causing these clots. Whether in the air or in a car, it is good to take a break, stand, and stretch every couple of hours."

In addition to moving around, it's advisable for passengers to avoid the window seat, which can prevent people from getting up to avoid disturbing their seat mates.  

As far as surgical masks, Eccles said, they make little difference because it's still possible to contract the common cold virus through dehydrated eyes. 

Bunn said to compensate these ill effects avoid dehydrating beverages like alcohol, coffee, and soda and opt for plain old water instead.