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.

The NTSB gave an update on its investigation into the Potomac River crash between an American Airlines jet and an Army helicopter in January.

Voice recordings from the Black Hawk helicopter involved in the crash with a commuter plan in Washington, DC, on January 29 have been released by the NTSB in a briefing for reporters Friday.