The National Transportation Safety Board questioned witnesses Friday on collision avoidance technology and organizational systems to manage risk. It is the third and final day of investigative hearings probing January’s midair collision between a US Army Black Hawk helicopter and an American Airlines regional jet,

The NTSB is now reviewing three days of testimony from last week’s public hearings into the Jan. 29 midair collision near Reagan National Airport.

Investigators so far have highlighted several factors that may have contributed to the collision, which left 67 people dead.