Boeing has delivered versions of the new plane to numerous largest airlines, including American and Southwest, according to the company's website.
A union bulletin to pilots at American Airlines Group Inc. said the company hadn't provided details about the system with its documentation about the plane.
Now the investigation's focus appears to be expanding to the clarity of US-approved procedures to help pilots prevent the 737 MAX from over-reacting to such a data loss, and methods for training them.
A Southwest spokeswoman said the new automated maneuvering system was not included in the operating manual for MAX models.
The control feature - known as the maneuvering characteristics augmentation system, or MCAS - is created to guard against a stall by automatically pushing down the plane's nose under potentially hazardous aerodynamic conditions. "Maybe Boeing never thought that this kind of problem would occur".
"We are taking every measure to fully understand all aspects of this incident, working closely with the investigating team and all regulatory authorities involved", the company said, reiterating previous comments about the October 29 crash.
"This is the first description you, as 737 pilots, have seen", APA safety committee chairman Mike Michaelis told pilots in a November 10 advisory note obtained by The Washington Post and reported earlier by the Seattle Times. "Safety remains our top priority and is a core value for everyone at Boeing".
Abu Dhabi summit: Oil production cuts may be necessary
A decision is expected only when the OPEC and non-OPEC ministers meet in Vienna on December 5 to assess the global energy market. Meanwhile, Russian Energy Minister Alexander Novak said that he "would not want to focus purely on production cuts".
Last week, Boeing released a statement acknowledging that Indonesian officials had told the aircraft manufacturer about repeated errant data readings experienced by the plane.
Even though this problem was - according to investigators - not covered in the operating manual, pilots did have access to a checklist created to turn off errant systems when the plane started nosing downwards at the wrong time, said Soejono, a Lion Air instructor who like many Indonesians goes by one name. But if pilots did not know exactly what system was in place, or that the data being fed into the system was wrong, their reactions could be fatally muddled, aviation experts said. The manual update raised an outcry from pilots in the US. He said Boeing bulletins to airlines and pilots "point them back to existing flight procedures" to handle the kind of sensor problem suspected in last month's crash.
Boeing and the Federal Aviation Administration issued directives last week telling flight crews about the system, which is created to provide extra protection against pilots losing control.
To counteract the anti-stall system, pilots are advised to switch off electric motors in the aircraft's tail that are causing the plane's nose to pitch downward.
On Oct. 29, Lion Air Flight 610 plunged into the Java Sea shortly after takeoff from Jakarta.
It would need to be transported to Los Angeles and fitted to the aircraft, and this was likely to take several days to complete.