An investigation from the National Transportation Safety Board (NTSB) has found the pilot of a military chopper that collided with a passenger plane may have had disrupted radio transmissions

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,

The Black Hawk that collided with an American Airlines jet in January may not have had accurate altitude readings, investigators said.