Passenger Mark Pensiero said that for "four to five seconds ... the airplane kind of rotated a little bit. Everybody kind of let out a collective 'holy crap, what was that.'"
Thankfully, most of the passengers were wearing their seat belts because the incident happened at 17,000 feet as the plan was still ascending.
CNN safety analyst David Soucie said without that fact, the injuries could have been much worse.
SO WHAT EXACTLY IS TURBULENCE?
"Clear air turbulence, or CAT, is air movement created by atmospheric pressure, jet streams, air around mountains, cold or warm weather fronts or thunderstorms," the Federal Aviation Administration says on its website.
According to Soucie and the website AirSafe.com, slight turbulence brings vibrations, moderate turbulence can bring drops of 10 to 20 feet, and severe turbulence, which is rare, brings the potential for the plane to drop 100 feet or more.
"You could have 10,000 flight hours and only experience this maybe three or four times in your entire career as a pilot," Soucie said.
Since pilots sometimes can't see turbulence coming, it's crucial for them to share information with each other about bad patches from flight to flight.
In the Philadelphia flight, there had been some reports of light turbulence in the area, but nothing as severe as what the plane encountered.
SEAT BELT, SEAT BELT, SEAT BELT:
The only time the industry has seen fatalities and injuries from severe turbulence is when people are not wearing their seat belts, according to Soucie.
“You are dropping quite a ways out of the air. Whatever is not tied down, whoever doesn't have their seat belt on, is going to go up.”
Soucie said since turbulence can sometimes come out of nowhere, it's best to always keep your seat belt buckled.