Togiak, Alaska (KINY) Bad weather and poor decisions were to blame for the crash on October 2, 2016.
The National Transportation Safety Board said inadequate training contributed to the crash of the Hageland Aviation Services aircraft as it flew on a mountainside 10 miles northwest of Togiak.
Timothy Cline, 43, and Drew Welty, 29, the pilots, and Louie John, 49, a passenger, were killed.
The NTSB has investigated five other Hageland accidents from December 2012 through April 2014.
Hageland policies and training contributed to the accident, the board said. Pilots routinely were allowed to turn on an "inhibit" switch for the airplane's Terrain Awareness and Warning System. The system emits loud warnings when airplanes are within 700 feet (213 meters) of terrain.