Mr Tjahjono and investigator Nurcahyo Utomo told a press conference on Monday that the problem was similar on each of the four flights, including the fatal flight on October 29 that crashed shortly after takeoff killing all 189 people on board.

“There were four flights in all that suffered a problem with the airspeed indicator,” Tjahjono said.

“When there was a problem, the pilot would write it down and the mechanic would do (a repair) … Then the plane would be declared airworthy.”

The agency said it would probe what caused the indicator problem and whether proper repairs were done — including replacing the faulty component, he added.

It did not give more details and did not speculate on how the indicator problem may have played a role in the crash, as it continues to mine the cockpit voice recorder — seen as key to answering why a nearly brand new plane fell out of the sky.

Airspeed indicators have been around for decades to tell pilots how fast they are flying.

They are paired with separate indicators measuring the degree to which the nose is pointed up, down or level.

Modern jetliners have redundant measurements to help pilots spot and disregard a single reading that looks unlikely and possibly erroneous.

Speed-measuring systems consist of tubes and sensors that measure air pressure generated by the plane’s movement and compare it with surrounding air pressure.

They fail occasionally, especially in bad weather at high altitude, when the tubes located under the plane’s nose can become jammed with ice, preventing air from reaching the sensors.

The Lion Air flight took off in good weather.

Frozen pitot tubes were blamed for the 2009 crash of Air France Flight 447, which killed all 228 people on board.

The year before, the US Air Force said moisture in sensors caused the 2008 crash of a B-2 stealth bomber on Guam; both pilots ejected safely.

In 2015, a wasp nest plugged the sensors on an Allegiant Air jet leaving St. Petersburg, Florida, forcing pilots to cut the flight short and land in Orlando.

A problem with the airspeed system should not result in a crash under most circumstances, according to safety experts.

“If you were driving down the interstate and the speedometer failed, would you expect to crash the car?” said John Cox, a former airline pilot and now a safety consultant.

He said a faulty airspeed system might have contributed to the crash, but that based on what we know so far, it shouldn’t be considered the cause of the crash.

‘SPECIAL AUDIT’ FOR ‘EXPENSIVE LESSON’

The new details revealing an air speed indicator problem come after the government said it was launching a “special audit” of the budget carrier’s operations.

Lion’s earlier admission that the jet had a technical issue — and the captain’s request to turn back to the airport minutes before the crash — have raised questions about whether it had faults specific to one of the world’s newest and most advanced commercial passenger planes.

Flight JT610 sped up as it suddenly lost altitude and then vanished from radar 12 minutes after takeoff, with witnesses saying the single-aisle jet plunged into the water.

Lion has been a regular target of complaints about poor service, unreliable scheduling and safety issues, including a fatal 2004 crash.

“We will … conduct a special audit of the crews’ qualifications and staff communication,” transportation minister Budi Karya Sumadi told reporters on Monday as he announced the probe into Lion’s operations.

“This is a preventive measure …(The accident) is a very expensive lesson for us.”

Civil Aviation authorities in the United States and Europe were also being consulted for their help in the probe, he added.

ANGRY RELATIVES DEMAND ANSWERS

The stunning revelation came after angry relatives confronted the airline’s co-founder at a meeting organised by Indonesian officials.

At least 105 body bags containing remains of passengers have been collected and sent to the national police hospital in Jakarta for DNA testing, but so far just 14 people have been identified.

Search and rescue agency head Muhammad Syaugi tearfully apologised on Monday as relatives’ clamour for answers grew louder, with accusations that the pace of recovery is lagging.

“We are not perfect human beings,” he said, sobbing.

“We have flaws, but we (are) doing the best we can.”

Meanwhile, authorities have extended their search as they collect more body parts and shattered debris from the spot where the plane crashed during a routine one-hour flight from Jakarta to Pangkal Pinang.

And Indonesia’s government ordered an inspection of all Boeing 737 Max 8 planes in the country.

All were found to be airworthy although two required repairs for “minor” problems.

The accident has resurrected concerns about Indonesia’s poor air safety record, which until recently saw its carriers facing years-long bans from entering European Union and US airspace.