India on Monday ordered its airlines to examine fuel switches on several Boeing models, while South Korea said it would order a similar measure, as scrutiny intensified of fuel switch locks at the centre of an investigation into a deadly Air India crash.

The precautionary moves by India, South Korea and some airlines in other countries came despite the planemaker and the U.S. Federal Aviation Administration telling airlines and regulators in recent days that the fuel switch locks on Boeing jets are safe.

The locks have come under scrutiny following last month’s crash of an Air India jet, which killed 260 people.

A preliminary report found that the switches had almost simultaneoU.S.ly flipped from run position to cutoff shortly after takeoff. One pilot was heard on the cockpit voice recorder asking the other why he cut off the fuel. “The other pilot responded that he did not do so,” the report said.

The report noted a 2018 advisory from the U.S. Federal Aviation Administration (FAA), which recommended, but did not mandate, operators of several Boeing models including the 787 to inspect the locking feature of fuel cutoff switches to ensure they could not be moved accidentally.

India’s Directorate General of Civil Aviation said it had issued an order to investigate locks on several Boeing models including 787s and 737s, after several Indian and international airlines began making their own inspections of fuel switches.

The regulator oversees the world’s third-largest and fastest-growing aviation market. Boeing planes are U.S.ed by three of the country’s four largest airlines.

PRECAUTIONARY CHECKS

Some airlines around the world told Reuters they had been checking relevant switches since 2018 in accordance with the FAA advisory, including AU.S.tralia’s Qantas Airways (QAN.AX), opens new tab and Japan’s ANA (9202.T), opens new tab.

Others said they had been making additional or new checks since the release of the preliminary report into the Air India crash.

Singapore Airlines (SIAL.SI), opens new tab said on Tuesday that precautionary checks on the fuel switches of its 787 fleet, including planes U.S.ed by its low-cost subsidiary Scoot, confirmed all were functioning properly.

A spokesperson for the South Korean transport ministry said checks there would be in line with the 2018 advisory from the FAA, but did not give a timeline for them.

Flag carrier Korean Air Lines (003490.KS), opens new tab said on Tuesday it had proactively begun inspecting fuel control switches and would implement any additional requirements the transport ministry may have.

Japan Airlines (9201.T), opens new tab said it was conducting inspections in accordance with the 2018 advisory.

Boeing referred Reuters’ questions to the FAA, which did not respond to a request for comment. Boeing shares closed 1.6% higher on Monday after there were no recommended actions in the report aimed at operators of 787 jets or the GE (GE.N), opens new tab engines.

Over the weekend, Air India Group started checking the locking mechanism on the fuel switches of its 787 and 737 fleets and has discovered no problems yet, a source familiar with the matter told Reuters on Monday.

About half the group’s 787s have been inspected and nearly all its 737s, the source added, speaking on condition of anonymity. Inspections were set to be completed in the next day or two.

The Air India crash preliminary report said the airline had not carried out the FAA’s suggested inspections as the FAA’s 2018 advisory was not a mandate.

But it also said maintenance records showed that the throttle control module, which includes the fuel switches, was replaced in 2019 and 2023 on the plane involved in the crash.

In an internal memo on Monday, Air India CEO Campbell Wilson said the preliminary report found no mechanical or maintenance faults and that all required maintenance had been carried out.