On October 15, 2017, at about 1022 universal coordinated time , Omni Air International, LLC, Boeing B-767-300ER, N342AX, was enroute to Daniel K. Inouye International Airport (DFS), Honolulu, Hawaii, when the flight encountered turbulence that caused serious injuries to one "deadheading" cabin crew member. None of the other 11 crew members were injured and the airplane was not damaged. The flight was conducted under the provisions of 14 Code of Federal Regulations Part 91 between Osan Air Base (OSN), Pyeongtaek, Republic of Korea, to DFS. As the flight was descending through about flight level 315 over the Pacific Ocean, approximately 117 miles from DFS, the airplane entered a thunderstorm cell and encountered severe turbulence that lasted about 30 seconds. When the turbulence was encountered, an off duty "deadheading" cabin crew member was in the aisle near the aft lavatory and was thrown to the floor injuring her right ankle. After being notified of the injury, the flight crew contacted telemedical advisory services via voice satellite communications and was provided medical direction to stabilize the injured crew member. Emergency medical personnel met the airplane on arrival and the injured crew member was transported to a local hospital where she was diagnosed with fractures in the right lateral and medial malleolus. Analysis of digital flight data retrieved from the Aeromechanical Systems Airborne Flight Information Reporting System (AFIRS) indicated that the airplane experienced vertical accelerations up to 1.78 g's and as low as 0.46 g's, with a change in rate of descent ranging from +240 feet per minute to -4,080 feet per minute. The flight crew reported no indication of precipitation or wind shear on the installed radar. The operator indicated that review of recorded telemetry reported by four other aircraft in the area equipped with The Weather Company Turbulence Auto-PIREP System (TAPS) showed no evidence of turbulence at the time of the accident.