When the plane started shaking violently on a Delta flight from Salt Lake City to Amsterdam last month, some passengers thought it was going to crash. The jet had hit severe turbulence, flinging people into the ceiling, and service carts across the cabin. One passenger said it felt like an earthquake. The plane was forced to make an emergency landing in Minneapolis, where 25 people were taken to the hospital. It was just the latest in a series of recent turbulence incidents resulting in injuries, hospitalizations and even a death. A 73-year-old man died of a heart attack during severe turbulence on a flight from London to Singapore last year. Turbulence, caused by disturbances in the atmosphere, is one of the most unpredictable weather phenomena for pilots. Air flows like water gushing down a river: undisturbed it runs smoothly, but if it encounters an obstacle, like a boulder, it becomes turbulent. Mountains and storms act like boulders in a river, altering the way air moves. Moderate to extreme turbulence happens tens of thousands of times a year across the world. For most passengers it will be felt as a few bumps, but in severe cases it can cause structural damage to the plane, temporary loss of control and injuries. Turbulence caused more than 200 serious injuries in the US alone between 2009 and 2024, according to data from the US National Transportation Safety Board. The good news is fatalities are very rare, and wearing a seatbelt almost always prevents serious injury. The bad news: Turbulence appears to be increasing, especially on some of the most heavily trafficked routes, and it's set to get worse as the planet heats up. So where can passengers expect the bumpiest trips? Swipe to learn more, and read the full story at the link in @cnn's bio. 📸: Illustration by Leah Abucayan/CNN | Obtained by KSTU | Graphics: Renée Rigdon, CNN | Jeff Greenberg/Universal Images Group Editorial/Getty