Investigation
The NTSB estimated the plane was traveling at a speed of approximately 200 knots (230 mph) when it impacted the water. The investigation was hampered by the fact that the flight data recorder (FDR) was not recovered intact from the wreckage, which was in muddy water 250 feet (76 m) deep. Portions of the FDR were recovered, but the recording media was never found.
Read more about this topic: United Airlines Flight 389