"The way the wind pattern flows across the mountains causes mountain wave turbulence,” said Tanya Gatlin, an aviation professor at Metropolitan State University of Denver. She also flies as an airline pilot.
"The pilots are trained to handle that and the airplanes are very much designed and built to be able to structurally support that jarring and that kind of turbulence," said Gatlin.
While the sudden shifts can be scary, pilots say the biggest threats are injuries inside the cabin.
In 2015, 21 passengers and crew members were hurt due to turbulence, according to FAA data. Thirty-one people were injured in 2014.
"When our seat belt signs are on, they're on for a reason, and it's in the interest of safety," said Gatlin.
Gatlin compares flying through turbulence to boating on rough water.
Pilots depend on reports from other crews in the sky in order to avoid it.
"We do everything we can to try and provide a smooth ride, whether that means climbing or descending, but sometimes on certain days, you just can't get out of it, no matter where you're at," Gatlin says.