U.S. District Court Judge Vaughn Walker ruled airlines that fail to warn passengers about the possible risk of deep vein thrombosis, a blood clot condition also called “economy class syndrome”, may face lawsuits.

Deep vein thrombosis is believed to affect people who sit in cramped conditions for long hours without exercise. Small blood clots form in the deep veins, particularly in the legs. The condition can be fatal if the blood clots break away and move into the lungs or brain.

“The risks of a blood clot go up astronomically after a flight of five hours or more,” Danko told Reuters.

“Short of redesigning seats and providing more room, airlines should tell people to get up and actually walk around — not exercise in seats — every hour and drink more water than they would otherwise be comfortable drinking, and completely avoid alcohol, which dehydrates the body,” Danko said.

(via Reuters)