The chairman of Indonesia's transportation safety agency has confirmed a third pilot was in the cockpit of a Lion Air Boeing 737 Max 8 on a troubled flight the day before the aircraft crashed minutes after take-off.
But Soerjanto Tjahjono, chairman of the National Transportation Safety Committee (NTSC), disputed reports citing recordings of cockpit discussions during the aircraft's final flight.
The third pilot, who has not been identified, was qualified to fly Max 8s and was on board the October 28 flight from Bali's Denpasar airport to Jakarta. He was not part of the official crew and was on board to reposition.
The aircraft encountered the same problems that appear to have caused it to crash a day later, but the three pilots aboard managed to resolve the issues and safely reached Jakarta.
Mr Tjahjono said the NTSC interviewed the pilot but legally cannot publish its findings.
Indonesian investigators say they are still analysing conversations from the October 29 flight recorded by the cockpit voice recorder that was only recovered from the sea bed in January.
Interest in the investigation into the crash off Indonesia's coast, which killed all 189 people aboard, has intensified following a crash of another Boeing 737 Max 8 in Ethiopia earlier this month that killed 157 people.
An earlier report issued by the agency describes technical problems aboard the plane's penultimate flight but does not mention that a third person was in the cockpit along with the pilot and co-pilot.
Mr Tjahjono said NTSC investigators have visited Boeing to carry out a reconstruction of that next-to-last flight. It will publish results of its investigation in August or September, he said.
A preliminary report from Mr Tjahjono's agency issued in December stopped short of declaring a probable cause of the crash. But it provided details about the pilots' struggle to fly the highly automated jet and Lion Air's difficulties with fixing sensors on the plane.
The Lion Air plane had issues on several flights before it crashed, with terrifying episodes of loss of altitude possibly related to an automated anti-stall system.
All Boeing 737 Max 8 aircraft have been grounded over safety concerns following the two crashes.
