A preliminary analysis of the flight data and voice recorder on board a Black Hawk helicopter leading up to the collision with a commercial flight over Washington, DC, on January 29, indicated the helicopter’s altimeter may have been inaccurate and the pilots may not have heard some calls from the Reagan National Airport control tower,

Investigators revealed on Friday the crew of the Army Black Hawk helicopter that collided in midair with an American Airlines jet near Ronald Regan National Airport in Washington, DC, last month may not have heard critical instructions from air traffic control prior to the fatal accident.