Pan American World Airways Flight 114, a Boeing 747-121, N739PA, was a scheduled passenger flight originating at John F. Kennedy International Airport (JFK), New York, on November 4, 1970. Its destination was Orly Airport, Paris, France. There were 148 passengers and a crew of 15 aboard the flight. The takeoff at 2117 EST was uneventful. The flight had been cleared to 31,000 feet, and turbulence during the climb to approximately 27,000 feet was described by the flightcrew as an occasional ?nibble.? At approximately 21:46 EST, the aircraft encountered moderate to briefly severe turbulence at about 27,000 feet as it passed Nantucket, Massachusetts. During the encounter, which lasted approximately 4 minutes 10 seconds, 21 passengers and two stewardesses sustained injuries which ranged from minor to serious. The seatbelt sign was on at the time of the encounter and had been on since takeoff. At 22:07 EST, the flightcrew requested clearance back to JFK Airport and later requested and received preferential air traffic control handling. The aircraft landed on runway 31R at 23:39 EST. The National Transportation Safety Board determines that the probable cause of this accident was the entry of the aircraft into an area of moderate to briefly severe turbulence associated with convective activity while numerous occupants were unsecured by seatbelts, even though the seatbelt sign was lighted.