On April 24, 2003, about 2235 eastern daylight time, a Fairchild-Dornier 328-300, N427FJ, operated by Atlantic Coast Airlines (ACA) as Delta Connection flight 6262, was not damaged after it encountered turbulence during cruise flight. There were no injuries to the two certificated pilots and five passengers; however, the flight attendant sustained serious injuries. An instrument flight rules (IFR) flight plan had been filed for the flight from Cincinnati/Northern Kentucky International Airport (CVG), Covington, Kentucky, to Roanoke Regional Airport (ROA), Roanoke, Virginia. Visual meteorological conditions prevailed for the flight conducted under 14 CFR Part 121. According to the captain, the flight was at cruise altitude at 22,000 feet in visual meteorological conditions. The airplane encountered a "light chop," so he kept the fasten-seatbelt sign illuminated. Without warning, the flight encountered "moderate turbulence" for 2 to 5 seconds. There was minimal altitude loss and the autopilot maintained control of the airplane. Following the turbulence encounter, the crew requested from air traffic control clearance to descend to 19,000 feet, where the remainder of the flight was smooth. The first officer provided a similar account of the events. In a written statement, the flight attendant stated that "continuous light turbulence" was encountered during the flight. While standing in the galley, the airplane suddenly encountered "severe clear air turbulence," which threw her against the bulkhead. As she regained her balance, the airplane encountered more turbulence, which knocked her to the floor. The flight continued to Roanoke Regional Airport and landed uneventfully. A review of the flight release that was issued to the pilots revealed a warning for occasional moderate turbulence below 12,000 feet for an area several hundred miles to the west of the airplane's route of flight. In addition, no SIGMETs or AIRMETs were issued for the Roanoke area.