NTSB: Severe turbulence on Delta flight hurled passengers into ceiling, hospitalizing 18

A preliminary National Transportation Safety Board report says violent turbulence on a Delta Air Lines flight July 30 tossed unbelted passengers into the cabin ceiling and back to the floor, injuring crew and passengers and prompting a diversion to Minneapolis.

The NTSB said the aircraft encountered about 2.5 minutes of rapid, unexpected turbulence while flying over Wyoming. The seatbelt sign was off and flight attendants had begun drink service when the airplane hit the severe storm cell. Paramedics evaluated 24 people after the diversion and 18 were taken to hospitals; two crew members sustained serious injuries and five crew members suffered minor injuries.

The NTSB report said passengers felt forces up to 1.75 times their body weight during the event. Aviation safety consultant and former NTSB and FAA investigator Jeff Guzzetti described that magnitude of force as "a lot of force" and said it would be enough to lift someone toward the ceiling and then slam them back down. The agency also reported the airplane’s wing dipped as much as 40 degrees during the encounter, a maneuver that would be noticeable and alarming to those on board.

Investigators charted the flight path over National Weather Service radar and found the aircraft flew into a bright red section of the weather map indicating intense storm activity. The pilot had requested a routing to avoid thunderstorms and had turned off the seatbelt sign before the turbulence began; the NTSB said the crew likely believed they were clear of hazardous weather at that time.

Passengers described repeated violent motions. "They hit the ceiling, and then they fell to the ground," passenger Leann Clement-Nash told ABC News. The report said carts also were thrown about the cabin.

The NTSB said it will examine whether the flight crew and other personnel took adequate measures to avoid the storms and whether the pilot’s decision to extinguish the seatbelt sign was appropriate. The agency’s preliminary report lays out the sequence and conditions but does not assign probable cause; further investigation and analysis of flight data and crew communications will follow.

Such in-flight injuries are uncommon, though they attract attention when they occur because of the potential for serious harm. Scientists and some aviation specialists have cautioned that clear-air and convective turbulence may be increasing in frequency and intensity as climate change alters jet-stream patterns, potentially exposing aircraft to more unexpected turbulence events.

The turbulence incident adds to a string of high-profile aviation accidents and emergencies this year that have heightened scrutiny of safety practices, including a midair collision over the Washington, D.C., area in January that killed 67 people and a March crash in Toronto that overturned an aircraft. The NTSB’s probe of the Delta flight will seek to establish what happened, why forecasts or radar did not prevent the encounter, and what steps might reduce the risk of similar injuries in the future.

Delta Air Lines did not immediately respond to a request for comment on the NTSB’s preliminary findings. The agency’s investigation will continue to collect and analyze data, interview crew and passengers, and review weather information and cockpit recordings as it works toward a final determination.