All 189 people aboard the Boeing 737 MAX vanished from radar about 13 minutes after taking off from Jakarta last October, slamming into the Java Sea moments after pilots had asked to return to the capital.

Several months later, an Ethiopian Airlines Boeing 737 MAX went down, killing all 157 people aboard and sparking a global grounding of 737 MAX airliners.

Nurcahyo Utomo, the National Transportation Safety Committee's lead investigator on the Lion Air crash, said Friday that the agency is still waiting for data from Boeing.

"When we get that data, it will go into our draft of the final report that we'll send to stakeholders, including Boeing, Lion Air and the US Federal Aviation Administration for feedback," he told AFP.

"I still hope we can release the final report in October."

Earlier Friday, Polana Pramesti, director general of Indonesia's civil aviation agency, had said she expected the report to be released by September.

Boeing -- hit by lawsuits and regulatory probes over the accidents -- was widely criticised over its development of the 737 MAX, with the focus on the Manoeuvering Characteristics Augmentation System (MCAS), a flight handling system linked to both crashes.

The MCAS pointed the plane sharply downward based on a faulty sensor reading in both accidents, hindering the pilots' effort to control the aircraft after takeoff.