It is the second of three days of witness testimony and public inquiry by the National Transportation Safety Board into the January midair crash over the Potomac River.

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,

A three-day National Transportation Safety Board hearing on the deadliest U.S. aviation accident in decades dug into problems with altimeters, chopper routes and the busy Washington, D.C., airspace.