Members of the search team lift part of the landing gear of the ill-fated Lion Air flight JT 610 during search operations at sea off the coast from Karawang on November 5, 2018.

Boeing shares rose Wednesday after a preliminary report from Indonesia investigators said the Lion Air 737 plane "was not airworthy" before its fateful flight.

Investigators are now looking at potential maintenance mistakes that may have led to the Oct. 29 crash that killed 189 people, according to The Wall Street Journal.

A pilot flying the jet the day before the crash chose to press on after shutting down the plane's anti-stall system, Nurcahyo Utomo, head of Indonesia's national transport safety committee, said at a news conference. Boeing further described the investigators' initial findings in a statement.

"The report explains that the maintenance logs for the accident aircraft recorded problems related to airspeed and altitude on each of the four flights that occurred over the three days prior to Flight 610," Boeing said. "The logs indicate that various maintenance procedures were performed, but issues related to airspeed and altitude continued on each successive flight."

Boeing's stock closed 4.9 percent higher on Wednesday. The company's shares had slid steadily since the crash, down more than 8 percent this month before Wednesday.

The Journal report said investigators suspect maintenance mistakes in the days before the crash may have led to the unexpected series of events that sent the plane in a steep dive into the Java Sea. Indonesian investigators said Wednesday they were looking at those maintenance actions.

"At this stage, we cannot determine if [the actions were] correct or not," Utomo said.

Following the Lion Air plane's flight the previous day, Boeing said "the pilot reported some of the experienced issues both on the aircraft maintenance log and to engineering."

"The report states that the pilot ran the runaway stabilizer non-normal check list, but it does not state that he communicated that fact in the maintenance documentation following that flight," Boeing said.

A final report is expected in the coming months but the investigation continues to be hampered by the missing cockpit voice recorder, which sank to the floor of the Java Sea after the crash.

– CNBC's Meghan Reeder and Reuters contributed to this report.

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