Last month, an American Airlines passenger jet and an Army helicopter collided as the plane prepared to land at Washington D.C.’s Ronald Reagan National Airport.

The National Transportation Safety Board provided an update on Friday into the investigation of the deadly Army Black Hawk helicopter and American Airlines flight collision.

The National Transportation Safety Board said the helicopter’s cockpit voice recorder didn’t capture key directions from air-traffic control and is investigating whether the crew might have seen a different altitude on the flight instruments.

That transmission was interrupted — it was stepped on,” said Jennifer Homendy, chair of the National Transportation Safety Board.

Officials at the National Transportation Safety Board said they are looking into the possibility that bad data caused inaccurate readings for the Black Hawk helicopter pilots in the January D.C. crash.