It is the second of three days of witness testimony and public inquiry by the National Transportation Safety Board into the January midair crash over the Potomac River.

The hearings in Washington will involve NTSB board members, investigators and witnesses. Panels will focus on military helicopter routes in the Washington area, collision avoidance technology and training for air traffic controllers at Ronald Reagan National Airport, among other subjects.

Investigators have found that a helicopter involved in a deadly crash with a passenger plane over Washington was flying above its height limit. The helicopter's altitude-measuring instrument was also inaccurate.