Boeing Co, the world's biggest planemaker, faces growing obstacles to returning its grounded 737 MAX fleet to the skies, while details emerged of an Indonesian crash last October with potential similarities to the Ethiopian disaster on March 10.
The investigation into the final minutes of Ethiopian Airlines Flight 302 turned on Tuesday to the secrets in the cockpit voice recorder as Boeing and a shaken global aviation industry hung on the outcome.
After Ethiopia, France and the United States all noted parallels with the Indonesia crash, one person familiar with the probe said black box data showed the Ethiopian Airlines jet's "angle of attack" was "very similar" to the Lion Air plane.
The plane then hit the water, killing all 189 people on board.
The first officer did not specify the issue, but a source said airspeed was mentioned in the voice recording. If it is too high, it can throw the plane into an aerodynamic stall.
As the captain tried to force the plane to climb, the plane's trim system continued to point it down. Normally, trim adjusts an aircraft's control surfaces to ensure it flies straight and level. "That was the only thing they talked about".
Representatives for Boeing and Indonesia's safety committee declined to comment on the earlier flight.
From July 2013 through March 2016, Hamilton served as the vice president of Safety, Security and Compliance and oversaw the Commercial Airplanes Organization Designation Authorization - a program that takes on specific safety certification duties on behalf of the U.S. Federal Aviation Administration.
Boeing has said there was a documented procedure to handle the problem. Bloomberg reported that the crew members got help from an off-duty pilot, who was on the same flight.More news: New Zealand bans sale of assault, semi-automatic rifles: PM
It has come to light that the 737 MAX involved in the Lion Air tragedy a year ago nearly crashed the day before. A crew that flew the same plane the evening before had the same problem with the plane's nose. When flight testing revealed an issue with meeting the certification standards, they developed a fix, Maneuvering Characteristics Augmentation System (MCAS), but did not tell airline pilots about it.
About one minute before the plane disappeared from radar, the captain asked air traffic control to clear other traffic below 3000 feet and requested an altitude of "five thou", or 5,000 feet, which was approved, the preliminary report said. "So you panic. It is a time-out condition".
The Indian-born captain was silent at the end, while the Indonesian first officer said "Allahu Akbar", or "God is greatest", a common Arabic phrase used to express shock, praise, distress or excitement.
The panel plans to call Boeing and other aviation manufacturers to testify amid a scramble to discover what caused the crashes of an Ethiopian Airlines flight last week and a crash involving Lion Air in Indonesia last October. They're also checking if the pilots were trained about the system. Airlines have some discretion to customize the manuals.
Various firms are reconsidering Boeing orders, and some airlines are revising profit forecasts given they now can not count on maintenance and fuel savings factored in from the MAX.
What happened to the Lion Air 737 MAX?
This is the first time that the presence of a third pilot in the cockpit has been disclosed. By that time, the investigators had already released an initial report of the accident, which relies heavily on flight data captured by the FDR.
Representatives of the Justice Department, the FBI and Transportation Department declined to comment, saying they could neither confirm nor deny an investigation.