The first of the National Transportation Safety Board’s three days of investigative hearings is underway to help determine what caused the deadly midair collision on January 29 between an Army helicopter on a training mission and American Airlines flight 5342 landing at Ronald Reagan Washington National Airport.

The hearings in Washington will involve NTSB board members, investigators and witnesses. Panels will focus on military helicopter routes in the Washington area, collision avoidance technology and training for air traffic controllers at Ronald Reagan National Airport, among other subjects.

On Wednesday morning, the NTSB released thousands of pages of evidence from the crash and the subsequent investigation -- including new video from the end of the runway showing the crash that killed 67 people.