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 NTSB has found discrepancies in the altitude reported by the Black Hawk crew and are investigating potential issues with barometric data

The National Transportation Safety Board says altimeter in the Black Hawk helicopter may have malfunctioned before the DCA mid-air collision with an American Airlines jet. All 67 people aboard died.