Kate Lamb in Jakarta and agencies – The Lion Air Boeing 737 Max jet that crashed in Indonesia on Monday flew erratically the previous evening and its air speed readings were unreliable, according to an accident investigator and a flight-tracking website.
According to data from FlightRadar24, the jet displayed unusual variations in altitude and air speed in the first few minutes of flight after taking off from Denpasar on the holiday island of Bali on Sunday evening – including an 875ft drop over 27 seconds when it would normally be ascending – before stabilising and flying on to Jakarta.
However, the pilots kept the plane at a maximum altitude of 28,000ft compared with 36,000ft on the same route earlier in the week.
The Lion Air CEO, Edward Sirait, told reporters on Monday a technical problem had occurred on the Denpasar-Jakarta flight but it had been resolved "according to procedure". Sirait did not elaborate and said he had no plans to ground the rest of Lion Air's Max 8 fleet.
The national transport safety committee (NSTC) deputy chief, Haryo Satmiko, told reporters on Tuesday there were technical problems on that flight, including unreliable air speed readings. "The suspected cause of the accident is still being investigated and it is making us all curious what could have caused it," he said. Satmiko gave no further details.
The Denpasar-Jakarta flight landed at 10.55pm local time on Sunday, giving engineers six-and-a-half hours at most for checks before it was dispatched for the Jakarta-Pangkal Pinang flight at 6.20am on Monday.
The plane plunged into the sea minutes after taking off from Jakarta. All 189 people onboard are believed to have died.
FlightRadar24 also reported unusual air speeds and altitudes in the few minutes that Flight JT610 was in the air. Two fishermen who saw the crash from their boat out at sea told Reuters the plane swayed slightly but made no noise as it fell, almost horizontal with its nose slightly down. There was an explosive sound as it plunged nose-first into the sea, followed by a column of smoke.
The weather was clear at the time of the crash at 6.33am on Monday, according to Satmiko, who said the pilots had requested a turnback to Jakarta.
Safety experts said the crash investigation was at a preliminary stage and it was too early to speculate about the cause. But pilot and engineering sources told Reuters the FlightRadar24 data for both flights, while not conclusive, could be a potential indicator of something wrong with the pitot-static systems. Those are pressure-sensitive instruments that feed air speed and altitude information to an avionics computer.
Authorities conducting a round-the-clock search for the bodies of the passengers on Flight JT610 were focusing on several areas off the coast of Java where they believe the body of the plane is located.
Search teams have so far filled 10 body bags. A further 14 bags filled with debris, including handbags, clothing, mobile phones, ID cards and driving licences, have also been collected.
One of those onboard was Bhavye Suneja, who lived in Jakarta with his wife of two years. The rest of his family live in Delhi. Kapish Gandhi, Suneja's cousin, said the family was devastated by the news and had gathered together in Delhi. "We saw it on the television this morning and didn't know whether to believe it," Gandhi said. "We are all speechless."
A second foreigner, a 26-year-old Italian national and former professional cyclist Andrea Manfredi is believed to be among those who were onboard JT-610.
The crash has renewed concerns about the safety of Indonesian airlines, soon after US and European regulators removed prohibitions against them.
The US and the European Union had banned Indonesian aircraft from their skies in 2007 after a string of accidents. The Federal Aviation Administration lifted the ban in August 2016.
In June, European regulators, who had already allowed Lion Air and a few other Indonesian carriers to resume flying to Europe, lifted their ban on remaining Indonesian carriers.
A spokesman said the European commission had no immediate plans to renew the ban on Lion Air, but the Australian government warned its officials and contractors not to fly on Lion Air pending findings from the crash investigation.
[Reuters contributed to this report.]