On June 22, 1996, approximately 1545 mountain daylight time, a Boeing 737-201, N207AU, operated by Frontier Airlines, Inc., as flight 328, in scheduled domestic passenger service, was not damaged when it encountered severe turbulence during descent over Granite, Colorado. One passenger received serious injuries, and one passenger and two flight attendants received minor injuries. There were no injuries to the airline transport-rated captain and first officer, and the other flight attendant and 91 passengers. Visual meteorological conditions prevailed, and an IFR flight plan had been filed. The flight was being conducted under Title 14 CFR 121, and originated in Albuquerque, New Mexico, on June 22, 1996, at 1505. According to the captain, he had begun the descent from FL290 into Denver and had been forewarned of reported turbulence. The "Fasten Seat Belts" sign was turned on, and flight attendants were instructed to be seated and to fasten their seat belts. An elderly woman got up and walked towards the aft lavatory. The airplane began to encounter light turbulence and a flight attendant attempted to seat the passenger in a flight attendant jump seat. Before her seat belt could be fastened, the airplane encountered severe turbulence and the passenger sustained a serious back injury. The flight attendant struck her head against the cabin ceiling, then struck her hip against the galley. At that time, the airplane was at FL240. Written statements were submitted by the three cabin crew members that corroborated the captain's report. The digital flight data recorder (DFDR) was removed from the airplane and sent to NTSB headquarters in Washington, D.C. for examination. According to the Flight Data Recorder Specialist's Report, the airplane was on a magnetic heading of 325 degrees, at 280 knots, and in a shallow descent from 29,000 feet when the DFDR recorded "violent vertical acceleration oscillations" that lasted approximately 150 seconds. Oscillation magnitudes ranged from +2.0 g's to -0.5 g's.