NTSB: Severe turbulence over Wyoming threw unbuckled passengers into cabin ceiling on Delta flight

The National Transportation Safety Board said Tuesday that passengers and crew aboard a Delta Air Lines flight bound for Amsterdam were violently thrown around the cabin when the plane encountered severe turbulence in a thunderstorm over Wyoming on July 30.

The preliminary report said the Boeing 767 experienced about 2.5 minutes of turbulence while the seat belt sign was off and flight attendants had begun drink service. Passengers who were not buckled were “thrown into the ceiling and back down to the floor,” the report said, and passengers felt forces up to 1.75 times their body weight. The flight diverted to Minneapolis, where 24 people were evaluated by paramedics and 18 were taken to hospitals. Two crew members sustained serious injuries and five sustained minor injuries.

Investigators mapped the aircraft’s path against National Weather Service radar and found the plane flew into a bright red section of the storm map, indicating the most intense part of the thunderstorm. The NTSB said the pilots had earlier requested routing around the storms and likely believed they were clear of the worst weather when they turned off the seat belt sign. The report said the airplane’s wing dipped as much as 40 degrees during the event.

Jeff Guzzetti, an aviation safety consultant who formerly investigated crashes for the NTSB and Federal Aviation Administration, said the duration and magnitude of the forces would have felt prolonged and violent to those aboard. “That’s like a muscle man grabbing you by the shoulders and with all of his strength trying to pull you up,” Guzzetti said, adding that standing passengers subjected to those forces would be thrown upward and then slammed back down.

The NTSB said it will investigate whether the flight crew and cabin crew took all appropriate measures to avoid the storm and whether turning off the seat belt sign before encountering the severe weather was prudent. The board characterized the report as preliminary; no probable cause has been determined.

Serious injuries from in-flight turbulence are relatively rare, but scientists and aviation experts have warned that a warming climate could change wind patterns and increase encounters with strong clear-air turbulence. The preliminary NTSB findings come amid heightened attention to aviation safety this year following several high-profile incidents, including a midair collision over Washington, D.C., in January that killed 67 people and a March crash in Toronto that seriously injured and killed passengers.

The investigation will continue as the NTSB gathers more data, interviews crew and passengers, and examines operations and weather information to determine contributing factors and safety recommendations.