The pilots of a doomed Lion Air Boeing 737 Max flight desperately scoured a handbook to find out why the jet was plummeting downwards but ran out of time before it crashed into the Java Sea, killing everyone on board.

According to three people who have heard a cockpit voice recording from the aircraft, the captain and first officer on board the ill-fated flight JT610 searched through checklists in a race against time after the jet warned them it was in a stall and pushed the nose down in response.

It has also emerged that an off-duty pilot riding along in the aircraft just a day earlier helped another crew save the plane from the same issue.

The investigation into the crash in Indonesia in October 2018, which killed all 189 people on board, has taken on new relevance since the model was grounded last week after a second deadly accident in Ethiopia on 10 March.

According to a preliminary report issued in November, the first officer on board the Lion Air flight last year reported a “flight control problem” to air traffic control just two minutes after take-off and said the pilots intended to maintain an altitude of 5,000 feet.

Lion Air plane crashes minutes after take-off from Jakarta Show all 13 1 /13 Lion Air plane crashes minutes after take-off from Jakarta Lion Air plane crashes minutes after take-off from Jakarta Indonesia President Joko Widodo inspects the items recovered from Lion Air flight JT 610 Getty Lion Air plane crashes minutes after take-off from Jakarta A member of Indonesian Search and Rescue Agency inspects debris AP Lion Air plane crashes minutes after take-off from Jakarta Rescue teams have been joined by fisherman and volunteers in the search for survivors Getty Lion Air plane crashes minutes after take-off from Jakarta Lion Air CEO, Edward Sirait (centre) speaks during a press conference at Lion Air Branch office at Soekarno Hatta Airport EPA Lion Air plane crashes minutes after take-off from Jakarta No bodies have yet been discovered among the wreckage of the Lion Air flight EPA Lion Air plane crashes minutes after take-off from Jakarta Indonesian search and rescue personnel prepare for a recovery mission Getty Lion Air plane crashes minutes after take-off from Jakarta Rescuers searching the site of the plane crash lift a body bag onto a nearby vessel EPA Lion Air plane crashes minutes after take-off from Jakarta A relative of passengers arrive at Lion Air's crisis center at Soekarno-Hatta International Airport in Tangerang, Indonesia AP Lion Air plane crashes minutes after take-off from Jakarta In this photo released by Indonesian Disaster Mitigation Agency rescuers inspect debris believed to be from a Lion Air passenger jet AP Lion Air plane crashes minutes after take-off from Jakarta A relative of passengers prays as she and others wait for news on a Lion Air plane that crashed off Java Island AP Lion Air plane crashes minutes after take-off from Jakarta A rescue team member points to the location where Indonesia's Lion Air flight JT 610 had crashed into the sea, at Tanjung Priok seaport in Jakarta Getty Lion Air plane crashes minutes after take-off from Jakarta Officials evacuate a body bag containing the remains of one of the victims of the crash EPA Lion Air plane crashes minutes after take-off from Jakarta Indonesian relatives of the plane crash victims cry as they wait for the news at the airport in Sukarno Hatta Airport EPA

The captain, who was at the controls, asked the first officer to check the quick reference handbook, which contains checklists for abnormal events, the first source with knowledge of the cockpit recording said.

For the next nine minutes, the jet warned the pilots it was in a stall and pushed the nose down in response.

The captain fought to climb, but the computer, still incorrectly sensing a stall, continued to push the nose down using the plane’s trim system, which usually ensures the aircraft flies straight and level.

The third source said: “They didn’t seem to know the trim was moving down. They thought only about airspeed and altitude. That was the only thing they talked about.”

The pilots of JT610 remained calm for most of the flight, the three sources told Reuters, and near the end the captain asked the first officer to fly while he checked the manual for a solution.

As the 31-year-old captain tried in vain to find the right procedure in the handbook, the 41-year-old first officer was unable to control the plane, two of the sources said.

“It is like a test where there are 100 questions and when the time is up you have only answered 75,” one of the sources said. “So you panic. It is a time-out condition.”

The Indian-born captain was said to be silent at the end before the plane hit the water, while the Indonesian first officer said “Allahu Akbar”, or “God is greatest”, a common Arabic phrase in the majority-Muslim country that can be used to express shock or distress.

Forensics investigators and recovery teams at the crash site of Ethiopian Airlines Flight ET 302 on 12 March 2019 in Bishoftu, Ethiopia. (Getty Images) (Getty)

The cause of the crash has not been determined, but a preliminary report mentioned the Boeing system, a faulty, recently replaced sensor, and the airline’s maintenance and training.

Boeing Co declined to comment while the investigation is ongoing, but the manufacturer said there was a documented procedure to handle the situation.

A different crew on the same plane the evening before encountered the same problem but solved it after running through three checklists.

However they did not pass on all of the information about the problems they encountered to the next crew, the November report said.

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Two of the sources said a captain at Lion Air’s full-service sister carrier, Batik Air, was riding along in the cockpit and told the crew how to disable the malfunctioning flight-control system and save the plane.

His presence on that flight, first reported by Bloomberg, was not disclosed in the preliminary report.

The report also did not include data from the cockpit voice recorder, which was not recovered from the ocean floor until January.

French air accident investigation agency BEA said on Tuesday the flight data recorder in the Ethiopian crash that killed 157 people earlier this month showed “clear similarities” to the Lion Air disaster.

Since the Lion Air crash, Boeing has been pursuing a software upgrade to change how much authority is given to the Manoeuvring Characteristics Augmentation System, or MCAS – a new anti-stall system developed for the 737 MAX.

Soerjanto Tjahjono, head of Indonesian investigation agency KNKT, said the report could be released in July or August as authorities attempted to speed up the inquiry in the wake of the Ethiopian crash.

On Wednesday, he declined to comment on the cockpit voice recorder contents, saying they had not been made public.