The pilots of a U.S. Army helicopter that collided with a passenger jet over Washington in January would've had difficulty spotting the plane while wearing night vision goggles, experts told the National Transportation Safety Board on Friday.

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 pilots of a Black Hawk helicopter that collided with a passenger jet near Washington Reagan National Airport in January never heard an air traffic controller's instruction to pass behind the jet,