Despite hitting turbulence so severe Monday it reportedly sent some passengers crashing into the ceiling, pilots on board the United Airlines flight did not address the situation on the intercom, a passenger told KUSA.
"I thought it was very interesting that the pilot never came on and said anything about what happened," Kerri Mullins told KUSA. "There was nothing."
Other passengers told KTVQ that it appeared the flight crew was just as surprised by the turbulence as the passengers.
"Nobody was really expecting [it], and I do mean nobody," Laurel Grant, a passenger, told the station. "I think the flight crew was probably in the same boat we were."
"I thought, 'Wow! Yeah, this is it'"
- Kerri Mullins, a passenger
Mullins, who was on the United Airlines flight from Denver to Billings, Mont., recalled the "most helpless" feeling when the plane hit severe turbulence for about 25 seconds.
She recalled the plane taking a hard right and starting to plunge. "People that did not have their seat belts on had flown out of their seats and hit the ceiling," she told the station.
"I thought, 'Wow! Yeah, this is it,'" Mullins told KUSA. "It's the most helpless feeling ever to just be sitting there and not having any control over anything."
United Airlines spokesman Luke Punzenberger told The Denver Post that three crew members and two passengers were injured. Federal Aviation Administration spokesman Ian Gregor told the Billings Gazette that the captain declared a medical emergency as the Boeing 737 approached Billings. The airline did not immediately respond to an email from FoxNews.com.
Gregor says Flight 1676 left Denver International Airport around noon and landed without incident just before 1:30 p.m. at Billings Logan International Airport.
Punzenberger says one flight attendant remained in the hospital late Monday. He says 114 passengers and five crew members were aboard. American Medical Response and the Billings airport fire department responded.
The Associated Press contributed to this report
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United Airlines pilots never spoke to fliers about severe turbulence, passenger ...

I have personally encountered turbulence like this while traveling in the winter to and from Hawai when I lived there from the West Coast of the U.S. Mainland. One time I watched a stewardess hit the ceiling and then land on passengers seat belted into their seats.

Ever since this experience of seeing this I tend to loosely have my seat belt on at all times unless I am walking to the bathroom on a plane.

Pilots may be aware of turbulence but often it can be a wind shear and not an ongoing event but one sudden drop of 100 to 1000 feet which will put anyone walking around on the ceiling of a plane. So, it isn't surprising to me that this could happen without the pilots telling people about it.

When you travel  be sure to look at weather events in your route of travel. If you see any big storms on your route be sure to loosely have your seat belt on at all times just for safety. Storms you can see on radar charts are usually the biggest causes of turbulence even though you might be flying over them.

When you are in ongoing turbulence the pilot usually says something but for a single event during extreme altitude loss they might not know it's coming either. 

Imagine you are on a plane where no one realizes they need to have their seatbelts on and this happens without warning. Under the right circumstances where literally everyone was thrown up and to the right or up and to the left, everyone might be unconscious or dead and this weight imbalance could cause the plane to eventually crash if attendants and other conscious passengers didn't immediately move those bodies for more equal weight distribution in the plane. In order to keep a fully loaded passenger plane stable in the air the weight has to be relatively balanced at all times in relation to the wings. If an unbalance occurs that is too extreme the pilot might not be able to keep the plane going in the right direction to fly or to land correctly. So, weight distribution is more important when flying than most people might realize in regard to forwards and backwards and to the right and left of the plane, especially for takeoffs and landings. As long as the plane is in the air sometimes weight imbalances are survivable but not during landings or takeoffs.