India’s aviation regulator has instructed airlines to inspect specific Boeing aircraft models following last month’s deadly Air India crash which killed 260 people.

On Monday, the Directorate General of Civil Aviation (DGCA) directed all carriers operating Boeing 787 Dreamliners and certain Boeing 737 variants to examine their fuel control switches. Airlines must complete inspections and report their findings by July 21.

The order comes after a preliminary investigation into the June 12 crash near Ahmedabad found both engines were deprived of fuel when the switches were flipped off almost simultaneously. The report, released last week, did not clarify how or why the switches moved from the “run” to the “cutoff” position mid-flight.

Fuel to Air India plane was cut off moments before crash, report says

The switches regulate fuel flow to the engines. The aircraft, a Boeing 787-8 Dreamliner, crashed shortly after takeoff, killing 241 of the 242 people onboard and 19 on the ground.

Investigators cited a 2018 U.S. Federal Aviation Administration advisory that recommended checking the locking mechanism of these switches on Boeing planes.

Cockpit audio recordings revealed a moment of confusion between the pilots, with one asking why the fuel had been cut. The other denied taking such action.

Some Indian aviation experts have suggested pilot error, though pilot unions strongly rejected such claims. The Indian Commercial Pilots’ Association condemned “reckless and unfounded” speculation, including theories of pilot suicide.

Air India CEO Campbell Wilson said the probe found no mechanical or maintenance faults with the aircraft. In a memo to staff, he noted the aircraft had passed all mandatory maintenance and safety checks, and the pilots were medically cleared.

Following the crash, Indian authorities ordered comprehensive checks of all 33 Dreamliners in Air India’s fleet.