Regulators in India and South Korea ordered inspections this week of fuel control switches on Boeing airplanes after a report on a deadly Air India crash showed that the plane’s fuel supply had been cut.

       Singapore Airlines also said on Tuesday that along with its low-cost subsidiary, Scoot, it had completed inspections of the switches on Boeing planes.

       Indian investigators’ preliminary assessment of the crash on June 12 of Flight 171, which was published on Saturday, did not draw any final conclusions about the cause. It appeared to rule out mechanical failure or design flaws, narrowing the focus to the fuel switches on the Boeing 787 jet that crashed.

       The most striking finding was that the two fuel control switches on the crashed jet were switched off seconds after takeoff, one after the other. Each switch is equipped with a locking mechanism to prevent accidental movement, leading experts to suggest it was unlikely they were moved without human involvement.

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       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 preliminary report said that Air India had not carried out the suggested inspections because they were not mandatory. The authors said that the F.A.A. had not viewed the concerns about the locking feature as serious enough to be considered unsafe.

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