The U.S. assessment is not contained in a formal document, said a source, who emphasized the cause of the deadly crash remains under investigation.

Sumeet Sabharwal, 56, was the captain on the flight, while Clive Kunder, 32, was the co-pilot who was flying the plane. Together, the two pilots had more than 19,000 hours of flight experience - nearly half of it on the Boeing 787. Both had passed all pre-flight health checks before the crash.

The deadly Air India crash last month has renewed a decades-old debate in the aviation industry over installing video cameras monitoring airline pilot actions to complement the cockpit voice and flight data recorders already used by accident investigators.