A cockpit voice recording of doomed Air India Flight 171 indicates the younger co-pilot asked his more experienced colleague why he turned off the plane’s fuel-supply switches, according to people familiar with the matter.

The report and India’s inspection order referred to an advisory from the Federal Aviation Administration in 2018 that recommended that carriers using Boeing models, including the 787, inspect the locking mechanism of the fuel control switches to ensure they could not be moved accidentally.

The release over the weekend of the preliminary report on last month’s deadly crash of an Air India flight has stirred controversy in the aviation community with some asserting that the crash could have been caused only by pilot suicide.