Crews move an engine recovered from the crashed Lion Air jet for further investigation on Nov. 4, 2018, in Jakarta, Indonesia. The Boeing 737 Max 8 jet plunged into the Java Sea minutes after takeoff from Jakarta early on Oct. 29, killing everyone on board.
That extra pilot, seated in the cockpit jump seat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia's investigation.
The next day, on Oct. 29, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.
The so-called deadhead pilot on the earlier flight from Bali to Jakarta told the crew to cut power to the motor driving the nose down, according to the people familiar, part of a checklist that all pilots are required to memorize.
"All the data and information that we have on the flight and the aircraft have been submitted to the Indonesian safety committee. We can't provide additional comment at this stage due the ongoing investigation on the accident," Lion Air spokesman Danang Prihantoro said by phone.
Boeing's 737 Max was grounded March 13 by U.S. regulators after similarities to the Oct. 29 Lion Air crash emerged in the investigation of the March 10 crash of Ethiopian Airlines Flight 302. In the wake of the two accidents, questions have emerged about how Boeing's design of the new 737 model were approved.
After the Lion Air crash, two U.S. pilots' unions said the potential risks of the system, known as the Maneuvering Characteristics Augmentation System hadn't been sufficiently spelled out in their manuals or training. None of the documentation for the Max aircraft included an explanation, the union leaders said.
Authorities have released few details about Ethiopian Airlines Flight 302 other than it flew a similar track as the Lion Air planes and then dove sharply into the ground. There have been no reports of maintenance issues with the Ethiopian Airlines plane before its crash.