Even if an angle of attack sensor on a jet is faulty, there's generally a backup system in place for the critical component, and pilots are trained to handle a plane safely if those sensors fail, airline safety experts said.
Under some circumstances, the Max jets will automatically try to push down the nose if they detect that an aerodynamic stall is possible.
Lion Air confirmed to CNN that the same aircraft was used on that route, and Indonesian authorities confirmed that the pilot on the flight reported a problem with one of the plane's instruments.
The bulletin combined with statements by Indonesian investigators to suggest that the pilots on the Lion Air 737 Max 8 were battling the plane as its computers commanded a steep dive during its final moments of flight.
Cox said that once investigators have all the data, they will work backward to determine if there was a problem with one of the plane's systems or if pilot decisions put the plane in peril.
The flight procedure recommendations to Boeing were based on how the flight crew responded to problems on the Bali-to-Jakarta flight, said investigator Nurcahyo Utomo.
So far, the U.S. Federal Aviation Administration, which certificated the 737 Max, hasn't taken any steps to require inspections of the plane.
It was not immediately clear whether the reported problem stemmed from a mechanical or maintenance issue, nor whether US authorities would order any checks. If pilots aren't careful, they can cause severe nose-down trim settings that make it impossible to level a plane.
Trump's trade war edgy for Republicans in U.S. midterms
Pennsylvania is one of the U.S. states where citizens are asked to vote for the Senate and the House of Representatives. In Georgia he introduced former University of Georgia football Coach Vince Dooley to address the crowd of supporters.
Such bulletins are routinely issued by aircraft and engine manufacturers, particularly in the wake of major events, and this one does little except to remind crews that the procedures for addressing this situation already exist.
"I'm still of the opinion that losing airspeed on the airplane shouldn't result in losing the airplane", Cox said.
The head of Indonesia's National Transportation Safety Committee, Soerjanto Tjahjono, said in the meeting that the data retrieved from flight data recorder found last week confirms reports that the altitude and the speed of the plane had been erratic. "Is this fatal? NTSC (National Transportation Safety Committee) wants to explore this", he said.
The Boeing 737 MAX has three such sensors but erroneous readings could cause it to point the nose down sharply in order to keep air under the wings and avoid a stall, according to a person briefed on the matter.
"If you were driving down the interstate and the speedometer failed, would you expect to crash the vehicle?" said John Cox, a former airline pilot and now a safety consultant.
Boeing says in the bulletin that if this failure arises, "initially, higher control forces may be needed to overcome any nose-down stabilizer trim".
Alan Diehl, a pilot and safety consultant, said the report that the same problem happened four times and was never fixed suggests that the problem may have been intermittent, making it harder to pin down.