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,

It is likely the Black Hawk pilots “stepped on” the communication for less than a second by pressing the microphone key to communicate back to the control tower, she said.