These were among the most serious injuries from turbulence aboard airliners last year, when the Federal Aviation Administration said the number of injuries doubled from a year earlier.

The 44 injuries in 2016 compared to 21 in 2015, the FAA announced Wednesday. During the last 15 years, the lowest total was 12 in 2006 and the highest was 107 in 2009, according to FAA.

Passengers tend to get injured more than crew members, and three-quarters of the injuries last year were for passengers. But crew members often suffer serious injuries because they frequently are standing or walking around the cabin when so-called “clear air” turbulence strikes unexpectedly.

The FAA urges passengers to listen to flight attendants and use an approved child-safety seat for children under 2 years old. The FAA also urges airlines to include turbulence in weather briefings, and to have pilots and dispatchers relay reports about turbulence.

Flight attendants said the incidents serve as a reminder of the risks of their profession – and the need for passengers to remain seated with their seat belts fastened during flights.

“The airplane cabin can be a dangerous work environment for flight attendants,” said Bob Ross, president of the Association of Professional Flight Attendants, the union representing crews at American Airlines. “Clear-air turbulence is particularly problematic and a leading cause of flight attendant injuries. By its nature, it is difficult or impossible to predict. That is why we stress that passengers keep their seat belts on whenever they are seated and pay particular attention to crewmember instructions during all phases of flight.”

The National Transportation Safety Board investigated airline turbulence incidents during 2016 including:

–On Dec. 13, a United Airlines flight from San Francisco to Denver hit mountain-wave turbulence and a “big jolt” at 20,000 feet. A flight attendant securing the galley in the Boeing 737-800 was thrown to the ceiling and then struck her face on a counter that gashed her cheek and fractured a facial bone.

–On Aug. 11, a JetBlue Airways flight from Boston to Sacramento encountered stormy weather above South Dakota. Three flight attendants and 24 passengers suffered minor injuries in the turbulence, and the Airbus A320 made an emergency landing in Rapid City.

–On Aug. 3, an American Airlines flight descending to the Cayman Islands bumped into 6 to 8 seconds of severe clear-air turbulence with no warning, despite using weather radar aboard the Airbus A319. The seat-belt sign had been on for 10 minutes, but five passengers and three crew members were injured. One passenger was taken to the hospital with a fractured vertebra.

–On July 28, a JetBlue flight from JFK to Barbados ran into clear-air turbulence with no warning from weather radar aboard the Airbus A321. A flight attendant carrying a pot of hot water swung the pot away from another crew member after one bump, but a sudden drop sent the pot into the air and scalded her left shoulder and side with second-degree burns.

–On July 26, a United flight hit a few seconds of turbulence at about 16,500 feet while the Embraer 170 descended into Cleveland. A flight attendant fell in the galley and broke her left tibia, and a doctor aboard the flight assisted her.

–On Jan. 15, pilots on a Southwest Airlines flight from Providence to Fort Lauderdale were warned about a weather front to the west of their path, but encountered 3 seconds turbulence over Titusville while beginning to descend. The seat-belt sign was illuminated aboard the Boeing 737-700, but a flight attendant securing the galley fell and broke her ankle.

“Airplanes have seat belts for a reason. Turbulence is a serious threat in the air and it cannot always be predicted,” said Sara Nelson, president of the Association of Flight Attendants-CWA. “It is one of the highest causes of serious on the job injury to flight attendants. The forces created in sudden clear air turbulence can throw bodies and unsecure items forcefully through the cabin much like the impact of a high speed collision. If you are not strapped in and secure, it could be deadly.”

IMAGE: Allegiant Air flight attendant Chris Killian prepares passengers for a flight May 9, 2013, before it pushes back from the terminal at McCarran International Airport in Las Vegas. The Federal Aviation Administration announced April 19, 2017, that 44 people were injured by turbulence during flights in 2016 — double the number from a year earlier. (Photo: DAVID BECKER, AP)

For more on this story go to: https://www.usatoday.com/story/travel/flights/todayinthesky/2017/04/21/faa-turbulence-injuries/100740982/