The big question in Air India Crash: If pilots didn't cut fuel, what caused both engines to shut down mid-air? Experts say 'cockpit conversation is alarming'
MUMBAI: If the pilots didn’t cut off the fuel, then how did the fuel supply to both engines cut off during the most crucial phase of flight? Was it a technical problem with the Boeing 787 Dreamliner?
The 15-page preliminary report released by India’s Aircraft Accident Investigation Bureau ( AAIB ) into the Air India AI-171 crash, which killed 270 people. The report was made public in the early hours of Saturday.
Fuel cut-off seconds after lift-off
About seven seconds after Air India flight AI-171 lifted off from Ahmedabad runway on June 12, the fuel to both engines of the Boeing 787 Dreamliner (VT-ANB) cut off. The shutdown happened within a time gap of one second.
"In the cockpit voice recording, one of the pilots is heard asking the other why he cut off the fuel supply. The other pilot responded that he did not do so."
This is the most critical piece of information in the report—fuel shut off seconds after take-off.
The only other logical possibility is one of the pilots cutting off the fuel supply and denying it. But the investigation veers toward an aircraft systems issue.
FAA warned of faulty fuel switch in 2018
The report refers to a 2018 Special Airworthiness Information Bulletin (SAIB) issued by the US Federal Aviation Administration (FAA), which warned of a fuel control switch locking malfunction in Boeing 787 aircraft.
However, the AAIB report states that Air India did not carry out the recommended inspection because it was advisory, not mandatory.
"As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory," the report said. Records indicate that VT-ANB underwent throttle control module replacements in 2019 and 2023, unrelated to fuel control switch faults, and no subsequent fuel control switch defects were documented after 2023, it added.
"At this stage of the investigation, no definitive cause has been determined, and no immediate safety recommendations have been issued to B787-8 or GEnx-1B engine operators," it said, adding that the Aircraft Accident Investigation Bureau (AAIB) of India, supported by NTSB-USA, Boeing, GE, FAA, and other international stakeholders, continues a detailed investigation focused on engineering, human factors, and system interactions.
TOI spoke to senior commanders and examiners, and they referred to another service bulletin issued jointly by FAA and GE (engine manufacturer) in 2021.
Service Bulletin FAA-2021-0273-0013 Attachment 2 recommends the replacement of the "MN4 microprocessor on ECU" with respect to engine fuel and control. It states: "This recommendation is to address a condition that may affect Flight Safety... Accumulated thermal cycles of the EEC with age causes the solder ball to fail."
Timeline of the crash
This is the sequence of events from the AAIB report:
08:07:37 UTC – Aircraft began take-off roll
08:08:33 UTC – Aircraft reached V1 speed (153 knots IAS) — the speed at which take-off must continue
08:08:35 UTC – Reached Vr speed (155 knots IAS) — pilots pulled back the control column
08:08:39 UTC – Air/ground sensors switched to ‘air’ mode — aircraft had lifted off
08:08:42 UTC – Aircraft reached maximum airspeed (180 knots IAS)
Immediately after – Engine 1 and 2 fuel cut-off switches moved from RUN to CUTOFF, one second apart
Engine parameters N1 and N2 began dropping as fuel supply ceased.\
"The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift-off. No significant bird activity is observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall," the report says.
Experienced crew on board
The commander had over 15,000 flying hours, including 8,600 on the B787, while the co-pilot had 3,400 hours. The co-pilot was Pilot Flying (PF) and the captain was Pilot Monitoring (PM).
Possible link to microprocessor fault
Senior commanders TOI spoke to referred to another technical alert: a 2021 joint bulletin by the FAA and GE (the engine manufacturer), recommending replacement of the “MN4 microprocessor” on the engine’s Electronic Control Unit (ECU).
“This recommendation is to address a condition that may affect Flight Safety… Accumulated thermal cycles of the EEC with age causes the solder ball to fail.”
The ECU is the "brain" of the jet engine, controlling parameters like fuel flow and managing fault detection. The MN4 microprocessor interprets data and commands fuel metering valves.
One commander explained:
"The microprocessor is mounted on a Ball Grid Array (BGA), which uses tiny solder balls to attach the chip to the circuit board. As the aircraft flies, the engine experiences high temperature swings, constant vibration, and thermal cycling. Over time, this causes fatigue cracks in the solder balls, leading to intermittent electrical connections, loss of signal processing, and potential engine control faults."
A failing microprocessor could result in dual engine shutdown—a catastrophic failure.
Questions about CVR, RAT, and Emergency Locator
Capt Amit Singh, an air safety expert, questioned the AAIB’s timeline.
"The timeline given in the report is not tallying, especially after take-off when the RAT is shown deployed in the image, which means both engines have already failed. It does not match with the engine failure timings given in the report," he said.
"What was happening in the ten seconds after the fuel cutoff switch was off? The report doesn't give information on the conversation in the cockpit. The two sentences from the CVR mentioned in the report about a pilot enquiring who cut off the fuel also don't carry a timestamp."
Capt Sam Thomas, President of the Airline Pilots’ Association of India (APAI), said, "The conversation between the pilots enquiring who cut off the fuel control switch is alarming."
He also flagged another issue: the Emergency Locator Transmitter (ELT) failed to work.
"It should emit signals if the force of impact is between 3.2 to 3.5 G; the impact of the accident would have been exponentially higher."
Doubts over investigation expertise
Capt Thomas also questioned the makeup of the investigating team:
"Who is the expert in this group? It is assumed that some B787 Dreamliner pilots have been... Why the secrecy? We know pilots in India, and none of them have been consulted. IAF pilots are not competent enough to investigate and understand modern aircraft operated by civilian airlines."
In response, the AAIB clarified:
"The investigation team comprising Mr. Sanjay Kumar Singh as Investigator-in-Charge, Mr. Jasbir Singh Larhga as chief investigator and Mr. Vipin Venu Varakoth , Mr. Veeraragavan K , and Mr. Vaishnav Vijayakumar as Investigators. Experienced Pilots, Engineers, Aviation Medicine Specialist, Aviation Psychologist and Flight Recorder Specialists have been taken on board as Subject Matter Experts (SMEs) to assist the Investigation in the area of their domain expertise."
Final report due in 2026
The final AAIB report is expected by June 12, 2026. For now, the root cause of the tragedy that took 270 lives remains undetermined.
"At this stage of the investigation, no definitive cause has been determined, and no immediate safety recommendations have been issued to B787-8 or GEnx-1B engine operators," the AAIB said.
India, along with the US National Transportation Safety Board (NTSB), Boeing, GE, FAA, and other global agencies, continues to examine engineering flaws, human factors, and aircraft systems that may have triggered the dual engine flameout just seconds into flight.
The 15-page preliminary report released by India’s Aircraft Accident Investigation Bureau ( AAIB ) into the Air India AI-171 crash, which killed 270 people. The report was made public in the early hours of Saturday.
Fuel cut-off seconds after lift-off
About seven seconds after Air India flight AI-171 lifted off from Ahmedabad runway on June 12, the fuel to both engines of the Boeing 787 Dreamliner (VT-ANB) cut off. The shutdown happened within a time gap of one second.
"In the cockpit voice recording, one of the pilots is heard asking the other why he cut off the fuel supply. The other pilot responded that he did not do so."
This is the most critical piece of information in the report—fuel shut off seconds after take-off.
The only other logical possibility is one of the pilots cutting off the fuel supply and denying it. But the investigation veers toward an aircraft systems issue.
FAA warned of faulty fuel switch in 2018
The report refers to a 2018 Special Airworthiness Information Bulletin (SAIB) issued by the US Federal Aviation Administration (FAA), which warned of a fuel control switch locking malfunction in Boeing 787 aircraft.
However, the AAIB report states that Air India did not carry out the recommended inspection because it was advisory, not mandatory.
"As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory," the report said. Records indicate that VT-ANB underwent throttle control module replacements in 2019 and 2023, unrelated to fuel control switch faults, and no subsequent fuel control switch defects were documented after 2023, it added.
"At this stage of the investigation, no definitive cause has been determined, and no immediate safety recommendations have been issued to B787-8 or GEnx-1B engine operators," it said, adding that the Aircraft Accident Investigation Bureau (AAIB) of India, supported by NTSB-USA, Boeing, GE, FAA, and other international stakeholders, continues a detailed investigation focused on engineering, human factors, and system interactions.
TOI spoke to senior commanders and examiners, and they referred to another service bulletin issued jointly by FAA and GE (engine manufacturer) in 2021.
Service Bulletin FAA-2021-0273-0013 Attachment 2 recommends the replacement of the "MN4 microprocessor on ECU" with respect to engine fuel and control. It states: "This recommendation is to address a condition that may affect Flight Safety... Accumulated thermal cycles of the EEC with age causes the solder ball to fail."
Timeline of the crash
This is the sequence of events from the AAIB report:
08:07:37 UTC – Aircraft began take-off roll
08:08:33 UTC – Aircraft reached V1 speed (153 knots IAS) — the speed at which take-off must continue
08:08:35 UTC – Reached Vr speed (155 knots IAS) — pilots pulled back the control column
08:08:39 UTC – Air/ground sensors switched to ‘air’ mode — aircraft had lifted off
Immediately after – Engine 1 and 2 fuel cut-off switches moved from RUN to CUTOFF, one second apart
Engine parameters N1 and N2 began dropping as fuel supply ceased.\
"The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift-off. No significant bird activity is observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall," the report says.
Experienced crew on board
The commander had over 15,000 flying hours, including 8,600 on the B787, while the co-pilot had 3,400 hours. The co-pilot was Pilot Flying (PF) and the captain was Pilot Monitoring (PM).
Possible link to microprocessor fault
Senior commanders TOI spoke to referred to another technical alert: a 2021 joint bulletin by the FAA and GE (the engine manufacturer), recommending replacement of the “MN4 microprocessor” on the engine’s Electronic Control Unit (ECU).
“This recommendation is to address a condition that may affect Flight Safety… Accumulated thermal cycles of the EEC with age causes the solder ball to fail.”
The ECU is the "brain" of the jet engine, controlling parameters like fuel flow and managing fault detection. The MN4 microprocessor interprets data and commands fuel metering valves.
One commander explained:
"The microprocessor is mounted on a Ball Grid Array (BGA), which uses tiny solder balls to attach the chip to the circuit board. As the aircraft flies, the engine experiences high temperature swings, constant vibration, and thermal cycling. Over time, this causes fatigue cracks in the solder balls, leading to intermittent electrical connections, loss of signal processing, and potential engine control faults."
A failing microprocessor could result in dual engine shutdown—a catastrophic failure.
Questions about CVR, RAT, and Emergency Locator
Capt Amit Singh, an air safety expert, questioned the AAIB’s timeline.
"The timeline given in the report is not tallying, especially after take-off when the RAT is shown deployed in the image, which means both engines have already failed. It does not match with the engine failure timings given in the report," he said.
"What was happening in the ten seconds after the fuel cutoff switch was off? The report doesn't give information on the conversation in the cockpit. The two sentences from the CVR mentioned in the report about a pilot enquiring who cut off the fuel also don't carry a timestamp."
Capt Sam Thomas, President of the Airline Pilots’ Association of India (APAI), said, "The conversation between the pilots enquiring who cut off the fuel control switch is alarming."
He also flagged another issue: the Emergency Locator Transmitter (ELT) failed to work.
"It should emit signals if the force of impact is between 3.2 to 3.5 G; the impact of the accident would have been exponentially higher."
Doubts over investigation expertise
Capt Thomas also questioned the makeup of the investigating team:
"Who is the expert in this group? It is assumed that some B787 Dreamliner pilots have been... Why the secrecy? We know pilots in India, and none of them have been consulted. IAF pilots are not competent enough to investigate and understand modern aircraft operated by civilian airlines."
In response, the AAIB clarified:
"The investigation team comprising Mr. Sanjay Kumar Singh as Investigator-in-Charge, Mr. Jasbir Singh Larhga as chief investigator and Mr. Vipin Venu Varakoth , Mr. Veeraragavan K , and Mr. Vaishnav Vijayakumar as Investigators. Experienced Pilots, Engineers, Aviation Medicine Specialist, Aviation Psychologist and Flight Recorder Specialists have been taken on board as Subject Matter Experts (SMEs) to assist the Investigation in the area of their domain expertise."
Final report due in 2026
The final AAIB report is expected by June 12, 2026. For now, the root cause of the tragedy that took 270 lives remains undetermined.
"At this stage of the investigation, no definitive cause has been determined, and no immediate safety recommendations have been issued to B787-8 or GEnx-1B engine operators," the AAIB said.
India, along with the US National Transportation Safety Board (NTSB), Boeing, GE, FAA, and other global agencies, continues to examine engineering flaws, human factors, and aircraft systems that may have triggered the dual engine flameout just seconds into flight.
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