Plane Down in the Tundra

S1, E4: September 15, 2015. In the dark, early morning hours on East Wind Lake, a Turbine Otter departs for a prime fishing spot on Cape Douglas, but it never arrives. Shortly after takeoff, the plane goes down in a remote area, leaving three dead. One survivor of the crash testifies that there was a mysterious sound shortly before the accident. However, it's a later discovery made by the NTSB Alaska Regional Office that blows the case wide open and reveals the preventable set of circumstances that led to the disaster.