The Ethiopian report was still being discussed between local investigators and external stakeholders, said a third person with knowledge of the matter in Ethiopia who also asked not to be identified.
Calls and messages outside regular working hours to Ethiopian investigators at the Ethiopian Civil Aviation Authority and Transport Ministry seeking comments were not immediately answered.
The NTSB continues to work with Ethiopian investigators “to assist them with completing the investigation, which includes reviewing their draft final report and providing our comments,” the U.S. agency said in a statement. “In accordance with the provisions in Annex 13 of the International Civil Aviation Organization, all investigative information will be released by Ethiopian authorities.”
Annex 13 governs how nations interact during international investigations. ICAO is an arm of the United Nations.
At least some disagreement has existed for months between officials in Ethiopia and the U.S. Investigators in Ethiopia had been prepared to conclude the cause of the crash a year ago, but held off issuing those findings after objections from the U.S. and France, Bloomberg reported.
The interim report issued in 2020 focused on Boeing’s design and contained little in the way of analysis of the pilots’ actions, and that needed to be addressed, people said at the time.
The crash followed another fatal 737 Max crash in Indonesia less than five months earlier and led to regulators grounding the model worldwide, plunging Boeing into crisis. The U.S. planemaker has since made revisions to the model and addressed safety concerns, and the jet was cleared to return to the skies in its home market late last year.
While regulators in the European Union, U.K., U.A.E. and others have since followed suit, others are more circumspect. China, a major market for Boeing, still has safety concerns and said this month it’s awaiting conclusions from the Ethiopia probe.
There’s little doubt that Boeing’s design of a flight-control feature known as Maneuvering Characteristics Augmentation System will be at the center of the cause of the Ethiopian crash.
After a malfunction, the MCAS system began driving down the plane’s nose repeatedly. The design lacked redundancy and Boeing failed to determine how pilots would react during the chaos it created as it failed, numerous investigations have concluded.
However, the Ethiopian pilots appear to have also made several missteps that exacerbated the failure, allowing their speed to get far too high and failing to make manual adjustments that could have halted the dives, according to preliminary data released by Ethiopia.
It was possible to deactivate MCAS by flipping two switches in the cockpit in a procedure pilots around the world were repeatedly drilled on. A crew aboard a Lion Air flight in Indonesia successfully followed these steps after encountering an identical failure the night before the same aircraft crashed off the coast of Jakarta.
The Ethiopian pilots followed the same steps initially, but reactivated MCAS and lost control, according to preliminary data.
Nations participating in a crash investigation in another country are permitted under ICAO’s Annex 13 to file the equivalent of a dissenting opinion, but it’s unusual and often signals tensions over how the probe was conducted.