You can imagine the screams when people were ejected from their seats without any warning about halfway through a 13-hour flight. Then, they had to sit on that plane for six more hours with no food or water; some of with injuries, just waiting to land, so they could see a doctor.
Flight attendants were in the middle of serving dinner when the roller coaster ride began.
"Suddenly there was a massive jolt," Cathay passenger Vincent Sunder said. "It was like the plane was almost dropping sideways."
Food was flying everywhere. And passengers were hanging on for dear life.
"For a couple of minutes we didn't quite understand what was going on," Sunder said. "The only thought was -- this aircraft is going down."
"Turbulence by itself is never going to knock an aircraft out of the sky, especially not a jetliner, but it'll feel that way and it's very very frightening," ABC News aviation analyst John Nance said. "Even to us up there in the cockpit for that matter."
Nance told us that turbulence is dangerous and this incident proves it.
The Boeing 747 was carrying 321 passengers and a 21 member crew. At least nine people were injured; eight of them sent to hospitals.
Nance says the danger is that on long overwater flights, like this one, turbulence can come out of nowhere.
"While most of this is predictable, some of it occasionally is not," he said. "That's why we keep saying -- keep those seatbelts fastened in flight when you're seated, even if the seatbelt light is off."
Some passengers said those who weren't belted in were thrown from their seats and crashed into the overhead bins.
It's the second time in a week major turbulence has injured air travelers.
The first came on a United flight Monday from Denver to Billings, Montana.
"Felt like something came up from the bottom and hit the bottom of the plane," United passenger Grant Linde said.
Laurel Linde added, " And then stuff and people were flying all over the place."
Five people went to the hospital, including two flight attendants.
In fact, of the 32 people injured each year by turbulence, 2/3 are crew members.
For it to happen twice in one week, Nance says that's a coincidence. But notes, "With global warming over time we're gonna get more energetic jetstreams, and the potential for these encounters will increase, as it will with the increase in air traffic worldwide."
In other words -- buckle up.