On September 29, 2004, about 1345 eastern daylight time, a Boeing 767-232, N109DL, registered to and operated by Delta Air Lines Inc., as a Title 14 CFR Part 121 scheduled international air carrier passenger flight from Atlanta, Georgia, to Aruba, Netherlands Antilles, had an encounter with turbulence, while over the Caribbean Sea. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed. The airline transport-rated pilot, first officer, 4 flight attendants, and 138 passengers were not injured. One flight attendant was seriously injured, and the airplane was not damaged. The flight originated in Atlanta, Georgia, the same day, about 1029. The captain stated that at the time of the accident they were in cruise flight at FL 370, in instrument meteorological conditions. He said they were about 130 miles north of Aruba, and the seat belt sign was illuminated, and in addition, he had made a public address informing the passengers of light choppy turbulence, and requested they stay seated with their seat belts securely fastened. He further stated that they then encountered very brief moderate turbulence, of about a 3-second duration, after which he called back to the cabin, and was told that a flight attendant had been injured. The first officer stated that he was the pilot-not-flying, and that prior to the turbulence event the captain had illuminated the seat belt sign, and had made a public address. The first officer said that he contacted the flight attendants via the interphone and told them that they should stay seated for a while. He said he then requested and received clearance to deviate around known weather ahead of their flight path. The first officer said that they did not penetrate any weather as seen on the airplane's display, but that they were in instrument meteorological conditions, and did not encounter turbulence. He said they returned to visual meteorological conditions momentarily, and then another cloud was in front of them , but there was no precipitation associated with that cloud on the radar display. He said there did not appear to be enough time to maneuver around this cloud, and was within the cloud for about 5 seconds at which time the turbulence occurred. He said they then received a call on the interphone that a flight attendant was in the aisle and appeared to be injured. One flight attendant stated that they were about 100 miles from landing the airplane encountered turbulence so strong that the cart in the aft galley toppled and injuries were suffered by three flight attendants. The flight attendant further stated that the time between the captains announcement to everyone to sit down and the actual turbulence was a mere few seconds. A second flight attendant stated that she along with two other flight attendants were in the aft galley when the seat belt light was turned on to indicate initial approach when about 20 minutes away from Aruba. She further stated that there was normal light chop as they prepared the galley for landing. In addition, all passengers were seated, when suddenly they encountered severe turbulence and the airplane dropped suddenly and jolted several times. She said that the other two flight attendants were thrown toward the 2 left door, and she was thrown to the 2 right door. A third flight attendant said that approximately 100 miles out from Aruba the captain turned on the seat belt sign and asked every one to be seated. She said the two flight attendants in the back were cleaning and stowing catering items and were not seated. Examination of the flight data recorder showed multiple vertical acceleration cycles between about positive 1.8 and 0.0 Gs, associated with the event.