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A pilot urged Ethiopian Airlines managers for more training on the Boeing 737 Max aircraft in an effort to prevent a crash similar to that of the doomed Lion Air flight in October that killed 189 people, according to emails and documents seen by Bloomberg News.

The pilot reportedly warned managers in December that more training was required. He also called for greater communication with 737 crew members, Bloomberg reported.

Three months after the pilot delivered the warning, Ethiopian Airlines Flight 302 crashed and killed all 157 people on board.

"It will be a crash for sure," the pilot said in an email in December, Bloomberg reported.

It is unclear whether the Ethiopian Airlines crash would have been prevented had the airline heeded the pilot's warnings.

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A pilot urged Ethiopian Airlines senior managers for more training on the Boeing 737 Max aircraft in December, two months after the Lion Air Flight 610 crash that killed 189 people, according to emails and documents seen by Bloomberg News.

Bernd Kai von Hoesslin, the Ethiopian Airlines pilot and a 737 instructor, reportedly warned managers that more training was required following the October Lion Air crash. He also suggested greater communication between crew members. Three months after von Hoesslin delivered the warning, Ethiopian Airlines Flight 302 crashed, killing all 157 people on board.

Von Hoesslin was concerned with how pilots would handle an issue with the 737 Max's flight-control feature in conjunction with cockpit warnings, according to the emails seen by Bloomberg.

"It will be a crash for sure," von Hoesslin said in an email in December, Bloomberg reported.

Read more: Boeing reportedly let some of its mechanics inspect their own work, and it's causing problems for the manufacturer at the worst possible time

Von Hoesslin also expressed his concerns on aircraft maintenance and pilot fatigue in 418 pages of communications. Von Hoesslin reportedly left the airline in April and included his previous advice with his resignation letter. He declined to comment for the Bloomberg story.

"Some of these concerns were safety-related and well within the duty of the airline to adequately address," von Hoesslin said in his resignation letter, according to Bloomberg.

An Ethiopian Airlines spokesman told Bloomberg they could not comment on the story.

Early investigations suggest that a faulty sensor played a role in both crashes. An issue with a sensor could have triggered an automated system meant to point the plane's nose downward to prevent the plane from stalling.

Von Hoesslin mentioned the automated system in his correspondence, though as Bloomberg noted, it is unclear whether the Ethiopian Airlines crash would have been prevented had the airline heeded his warning.

Boeing has been under intense scrutiny following the crashes. Multiple news reports have revealed issues in the production process, including for the 787 Dreamliner aircraft.

Errors on the production line included debris in airspeed sensors, rags and bolts in planes, and loose cabin seats, The Post and Courier reported earlier in May. Tires with cuts in them, untested gears, and malfunctioning hydraulics systems were also spotted by workers, some of whom were allowed to self-inspect their work.

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