The National Transportation Safety Board is examining "bad data" the crew of an Army Black Hawk helicopter may have relied upon prior to their deadly crash with a passenger jet outside Washington D.C.

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.