On May 15, 1997, at 1025 central daylight time (cdt), a Lockheed L-1011-385, N11003, operated and registered to Trans World Airlines, Inc., as revenue flight 327, experienced an in-flight separation of the left main landing gear strut door, while on approach to the Lambert Saint Louis International Airport, Saint Louis, Missouri. There were no injuries to the 11 crewmembers or the 176 passengers aboard the airplane. The aircraft was operating as a scheduled domestic passenger flight under the provisions of title 14 CFR Part 121. Visual meteorological conditions existed at the time, and an instrument flight plan was on file for the flight. The flight departed Orlando, Florida, at 0801 cdt, with a destination of Saint Louis, Missouri. According to the flight crew's written statements, at approximately 28 minutes after take off while passing flight level 28.5 for flight level 290, they heard a loud bang of short duration. All systems and flight controls were checked with a visual examination of the wings, and engines number one and three were checked and found to be normal. The Captain maintained .80 mach and flight level 290 for the en route portion of the flight. The Flight Engineer felt a slight vibration around seat rows 24 and 25 located on the left aisle area near the left wing. No other abnormalities were felt. The Captain used conservative speeds for landing configuration and an uneventful landing was made. The Flight Engineer discovered the missing left main landing gear strut door and under wing damage during his post flight inspection. The left main landing gear strut door was discovered approximately five miles away on an extended centerline to runway 30L to Lambert Saint Louis International Airport. The landing gear door landed in downtown Saint Louis at the corner of Tucker Boulevard and Market Street. The NTSB on-scene investigation began at 0900 on May 16, 1997 at the TWA maintenance facility located at Lambert Saint Louis International Airport. Examination of the lower forward mounting bracket revealed the mounting eyebolt had rounded threads and its associated hardware was misisng. The missing hardware consisted of a spacer, washer, castellated nut and cotter pin. All other mounting points revealed signs of overload fractures. The last maintenance performed in this area was on May 7, 1997.