The United Airlines jet was attempting to land when it was blasted by unstable air.
Fliers described a loud bang, then the plane dropped sharply enough to pull people of out their seats. Those on board said the plane seemed to be out of control for about a minute.
"There was a lot of screaming, a lot of hollering," one passenger said.
The baby girl was in the arms of a parent when a nasty bump wrenched it away and sent it flying back two rows from the original seat.
Fox 31 in Denver reports it took a few minute for the parents to find the child.
Bill Dahlin was on-board Flight 1676.
“I think they were somewhat panicked,” he told KTVQ.
“I think they were trying to assess things themselves, so they really didn’t offer any explanation because of what happened so quickly.”
Dahlin said one woman was thrown into the ceiling so violently that it cracked the panel.
The Federal Aviation Administration released a statement saying the pilot “declared a medical emergency after a flight attendant was injured by turbulence. The plane landed in Billings without incident.”
The plane was headed to Billings, Montana, and eventually landed there. Once on the ground three crew members and two passengers were sent to the hospital. One flight attendant is said to remain in critical condition.