The aircraft used for Lion Air flight JT610, which crashed into the Java Sea 13 minutes after taking off from Jakarta to Pangkalpinang, Bangka Belitung Islands, on Oct. 29, was unairworthy, the National Transportation Safety Committee (KNKT) has revealed.

The KNKT released its report on Wednesday, 30 days after the accident occurred and took the lives of 189 people on board — comprising eight flight crew and 181 passengers, including three minors.

The report consists of facts and evidence gathered by the committee, including the aircraft’s latest maintenance record, a detailed communication record between cockpit crew members and air traffic control minutes before the crash, as well as data downloaded from the flight data recorder (FDR).

While presenting the report, KNKT investigator Nurcahyo Utomo said the aircraft had malfunctioned during a flight from Denpasar, Bali, to Jakarta, the night before the incident.

“The FDR recorded that the plane’s stick shaker was active prior to and during the flight from Denpasar,” Nurcahyo said.

A stick shaker is a device that warns the pilot of an imminent stall.

According to data from the FDR, the very same problem occurred right before the aircraft took off for Pangkalpinang.

The stick shaker remained active until the crash.

Apart from the stick shaker, the pilot of the Denpasar flight noted several other warning signs that appeared on the flight display, including one concerning a difference in airspeed.

The pilot also noticed the airplane’s automatic trim system pushing the nose down.

The copilot reacted by turning off the autopilot and flying the aircraft manually until it safely landed in Jakarta.

“Referring to civil aircraft airworthiness and the operation manual [...], the pilot in command shall discontinue the flight when unairworthy mechanical, electrical or structural conditions occur,” the committee wrote.

“This condition [stick shaker problem] is considered unairworthy and the flight should not have been continued.”

After landing, the pilots who flew the airplane from Denpasar to Jakarta reported the malfunction to engineers, who carried out a number of maintenance checks on the aircraft before it was used for the JT610 flight.

The committee also found at least six malfunctions in previous flights since Oct. 26.

Nurcahyo added that every airplane experiencing recurring problems in a short span of time should get “special treatment” before being allowed to fly again.

Lion Air president director Edward Sirait denied the KNKT’s claim that the aircraft had been experiencing problems, saying that “before flying from Denpasar, the airplane was checked for its airworthiness and eventually allowed to fly by our engineers, according to procedure”.

Prior to releasing its report to the public, the KNKT had presented its findings to the victims’ family.

The report was presented in closed-door meetings in Jakarta and Pangkalpinang on Tuesday.

Intan Indah Syari, 26, who lost her fiancée Rio Nanda Pratama in the crash, said she expected more information from authorities.

“I was hoping for answers. There are so many questions in my head right now,” she said.

Dhani Dwi Raharjo, 32, who lost his wife, also expected more action from the government.

In its report, the KNKT noted that Lion Air and its maintenance company Batam Aero Technic, Boeing co., the Federal Aviation Administration and the Transportation Ministry’s Civil Aviation Directorate General took “safety measures” after the accident, including by issuing a bulletin from Boeing addressing the sensor malfunction on the Boeing 737 MAX series.

The KNKT also recommended Lion Air to ensure “the implementation of the Operation Manual […] in order to maintain safety standards and to assist pilots in making proper decisions”.

The committee added that it would continue its investigation before drawing an official conclusion on the cause of the crash.

An investigating team is scheduled to fly to the United States next week to gather more information from Boeing.

The KNKT would also need to study data from the cockpit voice recorder, which remains missing, to draw a more comprehensive conclusion.

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