On May 13, 2005, approximately 1820 mountain daylight time, a McDonnell-Douglas MD-88, N949DL, operated by Delta Air Lines as flight 664, was substantially damaged when the forward pressure bulkhead was penetrated by the nose landing gear actuator rod during initial climb near Denver, Colorado. Visual meteorological conditions prevailed at the time of the accident. The flight was being conducted on an instrument flight rules flight plan under the provisions of 14 CFR Part 121. The 2 pilots, 3 flight attendants, and 93 passengers were not injured. The flight originated at Denver International Airport (DEN), Denver, Colorado, and was en route to Hartsfield International Airport (ATL), Atlanta, Georgia. Shortly after takeoff, the pilots heard a loud bang and the cabin lost pressurization. The pilots observed an unsafe nose gear indication. They placed the gear handle in the down position and got three green lights. The control tower confirmed that the landing gear were down when the aircraft performed a low pass. The flight made an uneventful landing at Denver Post-accident examination by maintenance personnel revealed a hole in the forward pressure bulkhead and broken nose gear actuator. The nose landing gear actuator piston rod had worn threads, and a key locking washer in the gear assembly was sheared. At the time of the accident, the aircraft had accumulated 41,789.9 hours and 32,669 cycles. According to Delta Air Lines, there was no maintenance history on the actuator, and they believed it was original equipment when the aircraft was delivered in February 1990. An FAA Airworthiness Directive required the material composition of the nose landing gear lock link be determined. Delta Air Lines provided maintenance records proving the aircraft was in compliance with this Directive.