At their closest points, helicopters and planes routinely flew within 75 feet near the airport, according to the NTSB.

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.

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,