NEW DELHI: New Delhi: The initial probe into the crash of AI 171 has revealed that three seconds after getting airborne from Ahmedabad on June 12, fuel supply to both engines of the Air India Boeing 787 operating as AI 171 got cut off. The engines’ fan speed began dropping and the aircraft weighing 213.4 tons — which was close to its maximum take off weight with 54,200 kg of jet fuel — started to lose altitude before crossing the airport perimeter wall. The reason: fuel cutoff switches of the London-bound Dreamliner’s engine 1 and 2 transitioned from “run” to “cutoff” position one after another with a time gap of a second.
How and why this happened is not yet known. But what it led to is: The pilots issued a “MAYDAY MAYDAY MAYDAY” call 26 seconds after getting airborne and after that the crash happened within six seconds.
The two pilots were taken aback by the unexpected fuel cutoff. “One of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so,” says the report prepared by the Aircraft Accident Investigation Bureau (AAIB) and made public early Saturday.
As a result the engines’ fan rotation speed (N1 and N2) started decreasing even as the ill-fated aircraft weighed 2,13,401 kg on take off — close to its maximum take off weight of 2,18,183 kg. “The aircraft achieved maximum recorded airspeed of 180 knots indicated air speed at about 08:08:42 UTC (Greenwich time) and immediately thereafter, the engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of one sec. The engine N1 and N2 (fan rotation speed of different stages) began to decrease from their take-off values as the fuel supply to the engines was cut off,” says the report.
The aircraft’s “Ram Air Turbine” (RAT) got deployed during the initial climb immediately after lift-off as “both engines’ N2 (fan rotation speed) values passed below minimum idle speed,” it says. No significant bird activity was observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall.
Ten seconds later (08:08:52 UTC) the engines’ fuel cutoff switches for one engine transitioned from CUTOFF to RUN, resuming fuel supply. Four seconds later the same happened for the other engine. Engine 1 “started to progress to recover” with the other re-introducing fuel to achieve the same. However, by then it was too late. Nine seconds later (08:09:05), pilots transmitted “MAYDAY MAYDAY MAYDAY”.
“The air traffic controller (responded).. did not get any response… observed the aircraft crashing outside the airport boundary, activated the emergency response. At 08:14:44 UTC, crash fire tender left the airport premises for rescue and firefighting.”
“After takeoff, the aircraft impacted the BJ Medical College hostel which is 0.9 nautical miles (1.6 km) from the departure end of runway… As the aircraft was losing altitude, it initially made contact with a series of trees and an incineration chimney inside the Army Medical Corps compound before” crashing on the hostel.
The AAIB report says “scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB (the ill-fated Dreamliner) in 2019 and 2023. However, the reason for the replacement was not linked to the fuel control switch. There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB.”
Why did the fuel cutoff switch transition from “run” to “cutoff” for both the engines on June 12 on the Dreamliner may be known once the ongoing probe is complete.
Without linking it to the cause, the report says US Federal Aviation Administration (FAA) had in Dec 2018 issued a Special Airworthiness Information Bulletin (SAIB) “regarding the potential disengagement of the fuel control switch locking feature. This SAIB was issued based on reports from operators of Model 737 airplanes that fuel control switches were installed with the locking feature disengaged. The airworthiness concern was not considered an unsafe condition that would warrant airworthiness directive (AD) by the FAA. The fuel control switch design, including the locking feature, is similar on various Boeing airplane models including part number 4TL837-3D which is fitted in B787-8 aircraft VT-ANB. As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory. The scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB in 2019 and 2023.”
Seconds to disaster (all times in IST): What happened?
Air India acknowledges report
Soon after the release of the report, Air India issued a statement acknowledging the report. "Air India stands in solidarity with the families and those affected by the AI171 accident. We continue to mourn the loss and are fully committed to providing support during this difficult time. We acknowledge receipt of the preliminary report released by the Aircraft Accident Investigation Bureau (AAIB) today, 12 July 2025."
Further assuring their cooperation with the investigation, it added, "Air India is working closely with stakeholders, including regulators. We continue to fully cooperate with the AAIB and other authorities as their investigation progresses. Given the active nature of the investigation, we are unable to comment on specific details and refer all such enquiries to the AAIB."
How and why this happened is not yet known. But what it led to is: The pilots issued a “MAYDAY MAYDAY MAYDAY” call 26 seconds after getting airborne and after that the crash happened within six seconds.
The two pilots were taken aback by the unexpected fuel cutoff. “One of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so,” says the report prepared by the Aircraft Accident Investigation Bureau (AAIB) and made public early Saturday.
As a result the engines’ fan rotation speed (N1 and N2) started decreasing even as the ill-fated aircraft weighed 2,13,401 kg on take off — close to its maximum take off weight of 2,18,183 kg. “The aircraft achieved maximum recorded airspeed of 180 knots indicated air speed at about 08:08:42 UTC (Greenwich time) and immediately thereafter, the engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of one sec. The engine N1 and N2 (fan rotation speed of different stages) began to decrease from their take-off values as the fuel supply to the engines was cut off,” says the report.
The aircraft’s “Ram Air Turbine” (RAT) got deployed during the initial climb immediately after lift-off as “both engines’ N2 (fan rotation speed) values passed below minimum idle speed,” it says. No significant bird activity was observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall.
Ten seconds later (08:08:52 UTC) the engines’ fuel cutoff switches for one engine transitioned from CUTOFF to RUN, resuming fuel supply. Four seconds later the same happened for the other engine. Engine 1 “started to progress to recover” with the other re-introducing fuel to achieve the same. However, by then it was too late. Nine seconds later (08:09:05), pilots transmitted “MAYDAY MAYDAY MAYDAY”.
“The air traffic controller (responded).. did not get any response… observed the aircraft crashing outside the airport boundary, activated the emergency response. At 08:14:44 UTC, crash fire tender left the airport premises for rescue and firefighting.”
“After takeoff, the aircraft impacted the BJ Medical College hostel which is 0.9 nautical miles (1.6 km) from the departure end of runway… As the aircraft was losing altitude, it initially made contact with a series of trees and an incineration chimney inside the Army Medical Corps compound before” crashing on the hostel.
The AAIB report says “scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB (the ill-fated Dreamliner) in 2019 and 2023. However, the reason for the replacement was not linked to the fuel control switch. There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB.”
Why did the fuel cutoff switch transition from “run” to “cutoff” for both the engines on June 12 on the Dreamliner may be known once the ongoing probe is complete.
Without linking it to the cause, the report says US Federal Aviation Administration (FAA) had in Dec 2018 issued a Special Airworthiness Information Bulletin (SAIB) “regarding the potential disengagement of the fuel control switch locking feature. This SAIB was issued based on reports from operators of Model 737 airplanes that fuel control switches were installed with the locking feature disengaged. The airworthiness concern was not considered an unsafe condition that would warrant airworthiness directive (AD) by the FAA. The fuel control switch design, including the locking feature, is similar on various Boeing airplane models including part number 4TL837-3D which is fitted in B787-8 aircraft VT-ANB. As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory. The scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB in 2019 and 2023.”
Seconds to disaster (all times in IST): What happened?
- Aircraft from Delhi lands in Ahmedabad as AI 423: 11:17 am
- Aircraft pushes back from Ahmedabad to takee off for London as AI 171: 1:18:38 pm
- Aircraft begins taxiing: 1:26:08 pm
- Starts take off roll at: 1:37:37 pm
- Aircraft lifts off at: 1:38:39 pm
- Maximum speed achieved and fuel cutoff switches transition from RUN to CUTOFF: 1:38:42 pm
- Both engines’ core parameters fal below minimum idle speed & RAT begins hydraulic power supply: 1:38:47 pm
- Engine 1 fuel cut off switch goes back to run: 1:38:52 pm
- Engine 2 fuel cut off switch goes back to run: 1:38:56 pm
- Pilots issue MAYDAY call : 1:39:05 pm
- ATC replies, gets no respond as plane crashes
- Flight data stops recording: 1:39:11 pm
Air India acknowledges report
Soon after the release of the report, Air India issued a statement acknowledging the report. "Air India stands in solidarity with the families and those affected by the AI171 accident. We continue to mourn the loss and are fully committed to providing support during this difficult time. We acknowledge receipt of the preliminary report released by the Aircraft Accident Investigation Bureau (AAIB) today, 12 July 2025."
Further assuring their cooperation with the investigation, it added, "Air India is working closely with stakeholders, including regulators. We continue to fully cooperate with the AAIB and other authorities as their investigation progresses. Given the active nature of the investigation, we are unable to comment on specific details and refer all such enquiries to the AAIB."
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