On March 28, 2009, at 1300 eastern daylight time, a McDonnell Douglas MD-88, N941DL, operating as Delta flight 1966, experienced inflight turbulence while on approach to Hartsfield Jackson Atlanta International Airport (ATL), Atlanta, Georgia. The captain, first officer, 2 flight attendants, and 132 passengers reported no injuries. One flight attendant received serious injuries, and the airplane sustained minor damage. The flight was operated as a commercial transport flight under the provisions of 14 Code of Federal Regulations Part 121 under instrument flight rules with a company flight plan in effect. Instrument meteorological conditions prevailed at the time of the accident. The flight originated from El Paso International Airport (ELP), El Paso, Texas, at 0941 EDT. According to the two non-injured flight attendants (FA), the flight crew had turned on the fasten seat belt sign and announced over the public address (PA) system that all passengers and all flight attendants were to be seated because they were getting ready to go through some "rough air." One FA was located in the first-class galley; she secured all loose items then sat down and strapped in. She stated that within a few minutes the airplane "dropped severely." The second FA stated that they were on initial approach to ATL when the flight crew announced over the PA for passengers and FAs to take their seats. The FA stated that it took about 1 minute to get everything put away in the galley. Then he and the third FA went to the aft jumpseat to be seated. Neither FA fastened their restraints. According to the second FA, a passenger was getting up to use the lavatory and "I told him to return to his seat. I also made a PA for all passengers to remain seated. A child in row 28 tried to get up and I got up and told his father and the child to remain seated. The child was up several times during the flight." Then he returned to the jumpseat next to the third FA. Within a minute or so there was a "jolt of turbulence." It lasted between 2 to 3 seconds. We both came off the aft jumpseat and it retracted into the stowed position. The third FA fell on her side and hit her elbow, shoulder, and head on the lavatory door. "It all happened so quickly. I got her on the jumpseat and buckled her in." I asked her if she was okay. The captain called back and asked us if we were all right. I told him that the third FA had hit her head and had a cut on her arm. The captain said that he would have paramedics meet the flight. According to the Delta Flight Safety representative, damage to the airplane was isolated to ceiling panels above the injured flight attendant's jumpseat. The panels were replaced and the airplane was returned to service. Prior to the accident, turbulence guidance in the Delta Airlines Onboard Manual (flight attendant manual), included, “flight attendants should be seated immediately when directed by the captain to take their seats due to moderate or severe turbulence.” As a result of the accident, Onboard Manual turbulence guidance was changed to include, “flight attendants must be seated with seat belts and shoulder harness secured during moderate/severe turbulence or when directed by the captain.”