The National Transportation Safety Board will question witnesses Thursday about air traffic control training, a key part of the investigation into January’s deadly midair collision at Ronald Reagan Washington National Airport.

Air traffic controller failed to notify commercial plane crew about approaching Army helicopter before Washington D.C. collision that killed 67 people, FAA official says.

Air traffic control managers told the National Transportation Safety Board that F.A.A. leaders rebuffed efforts over the years to address hazardous conditions that played a role in the Jan. 29 crash.