It also emerged on Wednesday that American pilots had warned of a control problem on the Boeing 737 Max airliner nearly a year before the crash in Ethiopia.
Pilots working for several US airlines reported to US authorities that the jet had a tendency to pitch its nose down as early as April 2018, according to Nasa files seen by US media.
In November, two incidents were reported to the Nasa-run Aviation Safety Reporting Database that involved problems in controlling the 737 MAX at low altitude just after take-off with autopilot engaged, according to documents published by US publications.
“We discussed the departure at length and I reviewed in my mind our automation setup and flight profile but can’t think of any reason the aircraft would pitch nose down so aggressively,” one pilot said.
Another pilot called the flight manual “inadequate and almost criminally insufficient”.
The concerns centred around the new Maneuvering Characteristics Augmentation System (MCAS) which pushes the nose of a climbing aircraft down to prevent it entering into a stall or losing lift. After the Lion Air crash, American pilots’ unions raised concerns over the MCAS system and claimed they had received insufficient training to retake control in the case of a malfunction.