What Mr. Haryo was describing, though he did not know it at the time, was a malfunction of MCAS, which automatically forces the plane’s nose down if data indicates that the jet is angled too sharply upward and might stall.

Nurcahyo Utomo, the head of the safety group’s air-accident subcommittee, said he first learned of the term MCAS from news reports.

“People immediately assumed this was a Lion Air problem, an issue with a terrible Indonesian airline,” said Gerry Soejatman, an Indonesian aviation analyst. “But when a brand-new plane crashes, you have to look at all the factors, including the possibility of a manufacturer problem or defect. And you have to look really carefully when that manufacturer isn’t providing all the answers.”

Days after Flight 610 crashed, Polana Pramesti, the head of Indonesia’s civil aviation authority, waited for visiting Boeing and F.A.A. officials to talk to her. As head of Indonesia’s version of the F.A.A., she wanted advice on whether to ground Max 8 jets in Indonesia. But the Americans, who did spend time with transportation safety committee officials, never came to her, she said.

The official in her office in charge of airworthiness and aircraft operation, Avirianto, who like many Indonesians goes by one name, fired off messages to the F.A.A. asking for an explanation of MCAS, which at the time was only vaguely understood, even by aviation experts, because Boeing had failed to put information about it in the plane’s manual.

Although he conducted four teleconferences with F.A.A. officials, Mr. Avirianto said he was never given a clear explanation of how MCAS worked or whether it was safe. “They kept saying they were still analyzing, evaluating,” he said. “We never received any guidance because there were never any clear answers for us.”