According to CBS News, a collision between two helicopters in January the resulted in the death of 12 marines was found to have been caused by pilot error, inadequate training, and an issue with command.
The collision between the two helicopters occurred on January 14 around 11 P.M. after two CH-53E helicopters did not return to the Kaneohe Bay Base after their scheduled training mission. The debris of the helicopters was spotted two-and-half miles off Oahu several hours later.
The findings of the collision suggest that during the training exercise pilots failed to maintain a necessary amount of distance between the two helicopters. The helicopter in training slammed into the lead helicopter resulting in the collision. No mechanical issues were found with either helicopter.
Also, officials investigating the collision determined that the training exercise should not have occurred in the first place as the unit commander had been fired days before the collision.
The helicopters destroyed in the crash were known as Super Stallions and were part of the 1st Marine Aircraft Wing at Marine Corps Base Hawaii. The marines who were killed were between 21- and 41-years-old and were from several states.
According to HelicopterSafety.org the following are common causes of helicopter accidents: