A tragic collision between an American Airlines plane and a Black Hawk helicopter in January claimed 67 lives. The crash occurred as the plane approached Ronald Reagan National Airport and the helicopter conducted a training mission.

Investigations revealed critical communication failures. National Transportation Safety Board Chairman Jennifer Homendy said, “We are looking at the possibility of there may be bad data.” Pilots misjudged their altitude, and crucial instructions from air traffic control were likely missed when the helicopter crew accidentally cut off transmissions.

Compounding the tragedy, the Black Hawk’s tracking system was turned off for training purposes, and the pilot reportedly ignored a flight instructor’s warning seconds before impact.

Brig. Gen. Matthew Braman emphasized the complexity, stating, “There were multiple things that, had any one of them changed, it could have well changed the outcome of that evening.”

Authorities continue to piece together the events that led to one of the deadliest aviation disasters in recent memory.