On December 3, 2010, at 1042 Coordinated Universal Time (UTC), a Boeing 767-3G5, N584HA, encountered clear air turbulence at 18,000 feet (FL180) after departing Tafuna/Pago Pago International Airport (NSTU), Pago Pago, American Samoa. The certificated airline transport pilot captain, first officer, an additional pilot, 6 flight attendants, and 172 passengers were not injured; 1 flight attendant received serious injuries, and another flight attendant and 1 passenger sustained minor injuries. The airplane was not damaged. International Lease Finance Corp., d.b.a. Hawaiian Airlines, operated the airplane under the provisions of 14 Code of Federal Regulations Part 121, as a passenger carrying flight. An instrument flight rules (IFR) flight plan had been filed. Night visual meteorological conditions prevailed for the flight that was destined for Honolulu International Airport (HNL), Honolulu, Hawaii. According to Hawaiian Airlines, while on climb-out shortly after departure, the flight experienced four “jolts” of turbulence, characterized as moderate in intensity. The captain reported clear skies, with thunderstorms in the area. The captain further reported that the seatbelt sign was illuminated in the cabin, and the passengers were in their seat. The two flight attendants who were injured were in the aft cabin, preparing a beverage cart. The flight data recorder (FDR) was secured and sent to the National Transportation Safety Board laboratory for readout. According to the FDR data, approximately 8 minutes after takeoff, as the airplane was about to pass through 19,000 feet, the airplane experienced perturbations in the acceleration parameters. The vertical acceleration parameter increased to +1.59 g’s and within 2 seconds decreased to +0.66 g’s. Vertical acceleration increased again to record a maximum value of +1.75 g’s and then decreased to record a minimum value of +0.05 g’s 2 seconds later. The lateral acceleration parameter registered a minimum of -0.16 g’s and a maximum of +0.14 g’s over the same period. The disturbance lasted less than 10 seconds, and there was a change in wind speed and direction evident around that time period. The airplane continued to climb, and the remainder of the flight was uneventful. According to satellite imagery, there was convective activity in the area; however, the location where the turbulence was encountered was free of convective activity. According to the staff’s meteorologist report (attached to the public docket), the airplane was ascending through/near a boundary defined by significant decrease in atmospheric moisture. These types of boundaries are conducive to the propagation of gravity waves. These waves can be generated by convection, which was occurring near the accident location. No radar data was available for the area at the time of the accident. There were no AIRMET’s or SIGMET’s for the time of the accident.