On June 12, 2025, Air India Flight 171, a Boeing 787-8 Dreamliner, crashed shortly after takeoff from Ahmedabad, India. The crash destroyed the aircraft, damaged multiple buildings, and claimed 279 lives.
In our first blog on this tragedy, we highlighted early theories based on initial reporting. Now, with the release of the preliminary investigation report from India’s Aircraft Accident Investigation Bureau (AAIB), we can address some unknowns from our earlier analysis to confirm or rule out several of those early theories. While the report resolves some questions, it also introduces a critical new development: both fuel cutoff switches were found in the OFF position, with no indication that the crew intended to shut them down.
Just like in any investigation—whether inside your own company or on this scale—early theories aren’t discarded, they’re tested. This post revisits the original unknowns, identifies what’s been confirmed or ruled out, and considers where the investigation will progress from here.
Working Back from the Evidence: Testing Early Theories
We’ve updated the Cause Map™ diagram using findings from the preliminary report. The sections below walk through major areas of uncertainty from the initial investigation—flap settings, takeoff configuration, mechanical issues, and fuel quality—and explain what the evidence now shows.
1. Flaps: Were They Set Incorrectly, or Retracted Prematurely?
What we asked: Could incorrect or premature flap retraction have led to the loss of lift?
What we know now: The flap handle was found set at 5 degrees, consistent with normal takeoff setting for a 787-8. This position was confirmed by flight recorder data, which showed the flaps remained at 5 degrees throughout the flight. Despite thermal damage to the handle, its position was firmly seated, indicating no movement post-takeoff.
Conclusion: The flaps were correctly set and not retracted early. We’ve crossed these causes off the Cause Map™ diagram and used evidence boxes to show that the evidence does not support premature flap retraction or incorrect flap settings.
Air India 171 11-Why Cause Map™: Flaps Up Ruled Out
*Click on above image to enlarge
2. Takeoff Configuration: Was the Plane Configured Appropriately?
What we asked: Were thrust, gear, or other critical systems misconfigured for takeoff?
What we know now: Flight recorder data confirms the thrust levers and flaps were set correctly. The landing gear lever was found in the “DOWN” position, but this likely reflects impact-related damage rather than pre-crash configuration. The report notes no anomalies in the takeoff configuration.
Conclusion: The aircraft was properly configured for takeoff. Again, we’ll cross out this possible cause and use evidence boxes to demonstrate why this cause has been ruled out.
Air India 171 11-Why Cause Map™: Takeoff Configuration Ruled Out
*Click on above image to enlarge
3. Condition of the Aircraft: Were There Mechanical Issues?
What we asked: Did a mechanical failure or external factor like a bird strike cause the crash?
What we know now: The aircraft had several active Minimum Equipment List (MEL) items, which are non-critical systems that are allowed to be temporarily inoperative still meeting safety requirements. These included:
- Flight deck door visual surveillance
- Airport map function, core network
- Flight deck printer
- Nitrogen generation system performance
The aircraft also had some cabin and cargo systems that were under Category D (deferred) MEL, all of which were within allowed dates. All applicable Airworthiness Directives (ADs) and service bulletins were complied with. Maintenance records showed no unresolved issues affecting flight or engine systems.
One relevant advisory is the 2018 FAA Special Airworthiness Information Bulletin1 (SAIB NM-18.33), which flagged a potential problem with the fuel control switch locking feature on the Boeing 787-8. We’ll dig into this later in the blog, but for now we’ll just note that the advisory was not mandatory, and Air India did not perform the recommended inspections.
CCTV footage showed no significant bird activity in the area.
Conclusion: The aircraft was airworthy. None of the MEL items were related to critical systems, and there is no evidence of a bird strike.
Air India 171 11-Why Cause Map™: Bird Strike Ruled Out
*Click on above image to enlarge
4. Fuel Quality: Was the Fuel Contaminated?
Question: Could fuel contamination have caused the sudden loss of engine power?
What we know now: Fuel samples taken from the bowsers and tanks used to refuel the aircraft have been lab-tested and found satisfactory. Only a small amount of fuel could be retrieved from the aircraft itself via the Auxiliary Power Unit [APU] filter and refuel/jettison valve in the left wing. At the time of this writing, those samples are still pending lab analysis.
Preliminary data shows both engines lost power rapidly and almost simultaneously. Specifically, both N1 and N2 speeds (the rotational speeds of the low-pressure and high-pressure compressor sections) sharply dropped below idle. That kind of sudden, symmetrical failure is unusual for fuel contamination, which typically affects one engine or causes progressive degradation.
Conclusion: While we’re still waiting on results from the onboard samples, the available evidence points away from fuel contamination as a cause. For now, we’ll leave the possible cause on the map, add the evidence we have with evidence boxes, and use an Info to Get box to note the evidence we need to obtain.
Air India 171 11-Why Cause Map™: Fuel Contamination Evidence
*Click on above image to enlarge
Narrowing the Focus of the Investigation
The preliminary report from AAIB provided evidence to rule out three of the early theories, and the fourth now looks unlikely. We’ve updated our 6-Why Cause Map diagram accordingly.
Air India 171 7-Why Cause Map™
*Click on above image to enlarge
The report confirms that the aircraft took off normally from Runway 23 and reached a maximum air speed of 180 knots. Seconds later, both engines lost thrust. The crew was confused, with one pilot asking, “Why did he cutoff?” and the other responding, “I did not do so.”
A critical finding is that, according to the report, the fuel cutoff switches were toggled from RUN to CUTOFF one second after the other—not simultaneously, like you’d expect from a mechanical failure.
NOTE: On page 14, the report states that the engines transitioned from RUN to CUTOFF with a time gap of “01 sec.” Later in the report, the wording shifts to “immediately,” leaving some ambiguity as to whether this was a typo. A 0.1 second gap might still suggest a mechanical issue, but a 1 second gap does not.
I don’t want to imply that this was done intentionally, but at this point, we can’t rule that out.
If you’re interested in the wreckage and recovery details from the incident, you can find those in the AAIB’s full preliminary report. But for now, let’s focus on the part of the report that may explain what happened with the fuel switches, and whether it connects to a known vulnerability in 787-8s.
Not Required, but Possibly Critical: SAIB NM-18.33
The preliminary report continually references SAIB NM-18.331, the 2018 FAA advisory I mentioned earlier. The SAIB wasn’t mandatory, but it may be the most important lead in this investigation.
Boeing’s fuel control switch locking feature is designed to require intentional movement (like lifting a switch past a stop) before it can transition from RUN to CUTOFF.
But the SAIB warned that if the locking mechanism on the fuel control switch is improperly installed or becomes worn, that resistance may disappear, making it easier for the switch to be moved unintentionally. There are three ways this could happen:
- Vibration: High-vibration phases, like takeoff, could jostle the switch.
- Inadvertent Contact: Crew might brush against the switch and accidentally trigger it.
- Other Physical Disturbances: Loose objects or maintenance activities could potentially move an unlocked switch.
The FAA did not consider the issue severe enough to issue an Airworthiness Directive (AD), since it was not classified as an "unsafe condition" requiring mandatory action. Instead, the agency recommended voluntary inspections to confirm the locking mechanism was properly engaged and encouraged upgrading older switches.
While the SAIB acknowledged the risk of unintended in-flight engine shutdowns, no such incidents had been reported at the time. This likely influenced the FAA’s decision to issue guidance rather than a requirement.
Updating the Cause Map™ with Confirmed Dual Engine Failure
Now, we’ll expand our Cause Map diagram with the dual engine failure confirmed by the preliminary report.
Air India 171 13-Why Cause Map™
*Click on above image to enlarge
Considering both engines failed, it may seem redundant to separate the right and left engine failures on our map, but here’s why we did it.
At this stage in the investigation, we don’t yet know if both engines failed for the same reason or if different factors were at play. We also don’t know whether a single cause is behind both switches being toggled, or if each switch was toggled by a different cause. Structuring the map this way gives us flexibility to expand as new details emerge.
Ultimately, the three different ways the switches could be inadvertently toggled all tie back to the same issue: the switch lock was ineffective, due to improper installation or wear over time.
Adding all these details brings us to our updated Cause Map diagram.
Air India 171 Detailed Cause Map™
Full Cause Map™ diagram is better viewed in the PDF report below
What Happens Next?
We’ve compiled a full Cause Mapping® report that walks through this incident step-by-step with a detailed timeline, rich cause-and-effect analysis, diagrams to visualize the sequence of events, annotated photographs, and much more.
Download the Air India Flight 171 Crash report to explore our analysis in depth.
The AAIB investigation is still ongoing. The preliminary findings have helped rule out some early theories and introduced new ones, but at this stage, the agency has not reached a conclusion as to why the fuel cutoff switches transitioned from RUN to CUTOFF.
For quick reference, here’s where the investigation stands today. View the AAIB report for more details.
Current Progress:
- The wreckage site was documented with drone photography/videography.
- Wreckage has been moved to a secure area near the airport.
- Both engines have been recovered and are quarantined for analysis.
- Components of interest have been identified and quarantined.
- Fuel samples from the bowsers and tanks used to refuel the aircraft were tested and found satisfactory.
- Small fuel samples retrieved from the APU filter and refuel/jettison valve of the left wing are awaiting lab analysis.
- Enhanced Airborne Flight Recorder (EAFR) data has been downloaded and is under review.
- Statements from witnesses and the surviving passenger have been obtained.
- Postmortem reports of the crew and passengers are being analyzed to corroborate aeromedical and technical assessments.
Next Steps:
- Additional evidence is being gathered based on preliminary findings.
- The investigation will continue to review and examine new information from all relevant stakeholders.
- No airworthiness directives or recommended actions have been issued for Boeing 787-8 and/or General Electric GEnx-1B engine operators and manufacturers.
Expect another update from us as new details come to light.
1 - 2018 FAA Special Airworthiness Information Bulletin (SAIB NM-18.33)
