DENVER (CBS4) – Colorado and the Rocky Mountains are among the worst areas for turbulence in the United States.

It’s a problem that injures dozens of passengers and crew members nationwide every year.

Many were surprised when Denver International Airport was built right where thunderstorms are spawned and waves of mountain air come crashing onto the Front Range.

It was so bumpy on a recent Southwest Airlines flight a flight attendant was knocked to the floor after being thrown towards the ceiling.

She got up and tried to make it to the rear of the plane but passengers told her to brace herself in the aisle.

“It was quite scary. I started praying,” said a passenger.

This happened over the mountains about a half hour before the scheduled landing in Denver.

It finally smoothed out enough for the attendant to cautiously rise from the security of the floor and make her way back to the galley.

One man also had to be escorted to his seat from the lavatory on that flight.

“I opened the door and all of a sudden the plane dropped 20 feet or something and I just grabbed onto the door and sat down and I went for a wild ride,” he said.

Just a few weeks earlier a United Airlines flight from Denver to Billings landed with several people injured after encountering rough air.

“I’ve never felt so helpless in my life,” said traveler Kerri Mullins.

Mullins was one of those injured on that flight.

“We were tilted onto our right side and started plunging. Everything flew out of everybody’s hands,” she said.

Five people were taken to the hospital.

What happened is a result of something called mountain wave turbulence, and if you have flown into Denver you’re probably aware of it.

CBS4 showed video of the flight to Dr. Bob Sharman who researches turbulence at the National Center For Atmospheric Research in Boulder.

He says to think of turbulence above the mountains like waves.

(credit: CBS)

(credit: CBS)

“The waves by themselves don’t affect the aircraft that much — the plane goes up and down — but it’s the breaking waves that makes those on a plane feel the turbulence,” said Sharman.

Most often turbulence is simply a nuisance, but when severe and extreme, people can get hurt.

Photos from a Cathay Pacific flight from San Francisco to Hong Kong earlier this year showed items scattered everywhere by severe turbulence.

Sharman’s forecasts are passed on to pilots through the Aviation Digital Data Service.

“Typically we are able to predict 60, 70 or 80 percent of turbulence levels that we call moderate or greater,” said Sharman.