A 3-D model created by The Times visualizes the helicopter pilots’ field of view minutes before a fatal crash with a jet in Washington.

A key safety system was turned off on the US Army helicopter that collided with an American Airlines regional jet last week near Washington’s Reagan Airport, killing 67. Senate Commerce Committee chair Ted Cruz told reporters the Black Hawk helicopter had turned off its automatic dependent surveillance-broadcast (ADS-B),

The Army pilots were juggling dark skies, low altitude, a busy airspace and a cockpit without certain traffic detectors before the helicopter’s midair crash with a regional passenger jet.