On June 12, Air India Flight 171, a Boeing 787-8 Dreamliner, departed Ahmedabad’s Sardar Vallabhbhai Patel International Airport at 1:39 pm, bound for London Gatwick. Within 32 seconds of takeoff, the aircraft crashed into a medical hostel near the airport, killing 241 of the 242 passengers and crew on board and 19 people on the ground.

The sole survivor was a British-Indian man seated in row 11A. This was the first fatal crash of a Boeing 787 since its commercial debut in 2011.

A probe report by the Aircraft Accident Investigation Bureau (AAIB) was released last night. The report points to a series of possibilities and also raises multiple questions on what transpired inside the doomed flight.

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The Takeoff and Aftermath

According to data extracted from the aircraft’s Enhanced Airborne Flight Recorder (EAFR), commonly referred to as the black box, Flight 171 carried out a routine takeoff. The Dreamliner accelerated to a takeoff speed of 153 knots or roughly 283 kmph. It then reached a maximum airspeed of 180 knots or roughly 333 kmph, climbing steadily as expected. The flap setting was recorded at five degrees, and the landing gear lever remained in the ‘DOWN’ position, both standard takeoff procedures.

Weather conditions posed no threat, skies were clear, visibility was good, and winds were light. Yet, within seconds, the fuel control switches for Engine 1 and Engine 2 moved from the “RUN” to “CUTOFF” position, one after the other, within a one-second interval.

These switches govern the flow of fuel to the engines, and their transition to “CUTOFF” halted the supply, causing both engines to lose thrust. The black box data shows that thrust levels began to decrease from their takeoff values almost immediately, triggering a rapid de-throttling process.

The Cockpit Exchange

The cockpit voice recorder (CVR), one of two black box components, captured a brief exchange between the pilots. Captain Sumeet Sabharwal, the commander and pilot monitoring (PM), and First Officer Clive Kunder, the pilot flying (PF), were both experienced and medically fit, with no reported issues that could have compromised their flying. As the engines faltered, one pilot — identity unconfirmed — asked, “Why did you cut off?” The other responded, “I didn’t.”

This dialogue is now at the centre of the investigation.

Was it a misunderstanding, an unacknowledged action, or an external factor beyond the pilots’ control? The fuel control switches on a Boeing 787 are not simple toggles.

Each switch features a guard rail. To move a switch from “RUN” (forward) to “CUTOFF” (aft), a pilot must lift and shift it downward. This design minimises the risk of accidental movement, such as a hand brushing against it during flight.

The switches for Engine 1 and Engine 2 are spaced approximately two to three inches apart, making it improbable for both to be moved simultaneously without intent. Yet, the data confirms that both transitioned to “CUTOFF” within a single second.

The Pilots’ Response

As thrust diminished, the aircraft’s altitude began to drop. The black box indicates that the pilots acted swiftly, moving both fuel control switches back to the “RUN” position. This action, executed approximately 10 seconds after the initial cutoff, aimed to restore fuel flow and restart the engines.

Engine 1 responded and its core speed deceleration halted, reversed, and began to recover, with thrust levels rising. Engine 2 also relit, but its core speed continued to decelerate despite repeated attempts to reintroduce fuel and accelerate recovery. The thrust levers, found near idle in the wreckage, had remained forward until impact, per the flight data recorder (FDR).

Simultaneously, the Ram Air Turbine (RAT), a small propeller deployed automatically in the event of dual engine failure, extended from the fuselage during takeoff. CCTV footage from the airport captured this deployment.

The RAT provides emergency power to sustain critical systems, but it cannot generate thrust. With the aircraft barely a few hundred feet above ground, the partial recovery of Engine 1 proved insufficient.

At 1:39:32 pm, Flight 171 struck the hostel, sparking a fireball that devastated the site.

The Key Focus

The AAIB’s preliminary report, spanning dozens of pages, drew on data extracted from the heavily damaged black box units, one located in the forward section, the other in the rear.

These devices, designed to withstand extreme temperatures and impact, house memory chips that record flight data. The National Transportation Safety Board (NTSB) of the United States provided specialised equipment to retrieve this data.

The investigation now centres on the fuel control switches. Three primary theories are under scrutiny:

Human Action: Did one pilot deliberately or inadvertently move the switches? The cockpit exchange suggests neither accepted responsibility.

“No pilot in their right mind would do this. The switches require intentional effort-lifting and moving them past a guard rail. It’s not a light switch you flick by mistake,” Captain Saurabh Bhatnagar, a former senior commander at Air India Express, told NDTV.

Mechanical Failure: Could a defect have caused the switches to move independently?

External Factors: Could fuel flow have ceased despite the switches remaining in “RUN”? The report finds no evidence of this.

The AAIB has ruled out other variables. No significant bird activity was detected, negating a bird strike theory.

The Auxiliary Power Unit (APU), a rear-mounted mini jet engine, was operational and attempted an autostart to assist engine relight, but its role was secondary to the switches’ position. Crucially, the report states there is “no immediate evidence of sabotage.”