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.

Long-standing concerns about military helicopters flying in crowded airspace and worries over short staffing among federal aviation workers have emerged as key factors in investigators’ inquiry into the fatal midair crash between an Army helicopter and a commercial airliner earlier this year.

The National Transportation Safety Board will wrap up its public testimony on Friday about the fatal midair crash between an Army helicopter and a commercial jet earlier this year