An off-duty pilot in the cockpit of the Boeing 737 MAX 8 that crashed in Indonesia the next day, killing 189 people, reportedly saved the plane the day before by telling the crew “how to disable a malfunctioning flight-control system.”

“As the Lion Air crew fought to control their diving Boeing 737 MAX 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit,” reported the South China Morning Post, Wednesday. “That extra pilot, who was 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, 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 South China Morning Post continued, adding that the “previously undisclosed detail on the earlier Lion Air flight represents a new clue in the mystery of how some 737 Max pilots faced with the malfunction have been able to avert disaster while the others lost control of their planes and crashed.”

This month, President Trump grounded Boeing 737 MAX 8 planes in the United States following the two crashes, which occurred within 5 months of each other.

Two MAX 8 aircraft, one operated by Lion Air and the other by Ethiopian Airlines, crashed, killing 189 and 157 people respectively.

On Thursday, CNBC reported that “Boeing jets in Ethiopia and Indonesia lacked two safety features in their cockpits because the company charged extra to install them.”

“The features could have helped pilots detect erroneous readings, which some experts believe might be connected to the planes’ failures,” CNBC declared.

At least 5 complaints from pilots were reportedly made about Boeing 737 MAX 8 aircraft before the crashes, with one describing the plane as “inadequate and almost criminally insufficient,” and another claiming it was “unconscionable” to allow pilots without special training to fly the planes.