Air India 171’s SOS signal was not immediately detected because the navigation system was blocked by an internal device
Aviation security experts are investigating the possibility of deliberate interference from inside the cockpit

Air India Flight 171: The Enigma of the SOS Signal and Suspected Cockpit Interference

On June 12, 2025, Air India Flight 171, a Boeing 787-8 Dreamliner, crashed 32 seconds after takeoff from Ahmedabad’s Sardar Vallabhbhai Patel International Airport, en route to London Gatwick. The disaster claimed 241 of the 242 passengers and crew aboard, along with 19 lives on the ground, when the aircraft slammed into the hostel block of B.J. Medical College. A preliminary report by India’s Aircraft Accident Investigation Bureau (AAIB) revealed that both fuel-control switches were moved to the “cutoff” position seconds after takeoff, starving the engines of fuel. However, a more recent and unsettling revelation has emerged: an SOS signal, transmitted 17 seconds before the plane lost contact, was not immediately detected due to interference from an internal device, raising suspicions of deliberate sabotage from within the cockpit. This signal, eerily matching the frequency of a 2017 crash, has deepened the mystery and prompted aviation security experts to investigate a chilling possibility: intentional interference.

The Crash and the Mysterious Signal

Flight 171 took off at 13:38:39 IST (08:08:39 UTC) under clear weather, piloted by Captain Sumeet Sabharwal (15,638 flight hours) and co-pilot Clive Kunder (3,403 hours). The aircraft reached 625 feet at 180 knots when, at 08:08:42 UTC, both fuel-control switches flipped to “cutoff” within one second, causing a dual-engine shutdown. The cockpit voice recorder (CVR) captured a brief exchange: one pilot asked, “Why did you cut off?” The other replied, “I didn’t.” Ten seconds later, the switches were returned to “run,” triggering an automatic engine relight, but the plane, already in a fatal descent, crashed at 13:39:11 IST.

The AAIB’s preliminary report, released July 8, 2025, noted the fuel switch movement but offered no explanation. A subsequent analysis, reported by BBC on July 22, 2025, uncovered a 1.3-second SOS signal transmitted at 08:08:54 UTC on 121.75 MHz, 17 seconds before contact was lost. This frequency matched one detected during the 2017 TransAsia Airways Flight 235 crash, where an unexplained radio interference was noted but unresolved. The signal’s initial nondetection was attributed to a blockage by an internal device, suspected to be within the cockpit, which disrupted the aircraft’s navigation and communication systems.

The Interference Hypothesis

Aviation security experts, including teams from the AAIB, the U.S. National Transportation Safety Board (NTSB), and the UK’s Air Accidents Investigation Branch, are now probing whether the interference was deliberate. The SOS signal, a structured pulse of modulated static, was not immediately picked up by air traffic control due to a temporary disruption in the aircraft’s transponder and communication systems. This suggests an internal device, possibly a portable electronic jammer or a manipulated cockpit system, may have been activated. Such devices can emit signals that overpower or mask critical frequencies, including the 121.5 MHz emergency band used for SOS transmissions.

The 2017 TransAsia crash provides a haunting precedent. That Boeing 737-800, which crashed 82 seconds after takeoff in Taipei, also transmitted a brief signal on 121.75 MHz, later attributed to possible external interference. The lack of resolution in that case has fueled speculation that Flight 171’s signal could indicate a recurring vulnerability in modern aircraft systems. Cybersecurity analysts, assisting the AAIB, are examining whether the interference originated from a compromised Full Authority Digital Engine Control (FADEC) system or another onboard device. A momentary FADEC spike, logged milliseconds before the fuel switch cutoff, falsely indicated a dual-engine flameout, potentially triggering an automated response or pilot confusion.

Cockpit Dynamics and Human Factors

The CVR’s ambiguous exchange—“Why did you cut off?” followed by “I didn’t”—has intensified scrutiny on the pilots. Captain Sabharwal, the monitoring pilot, and co-pilot Kunder, flying the aircraft, were both experienced and cleared for duty. The fuel switches, centrally located and equipped with lever-lock mechanisms, require deliberate action to move, making accidental activation unlikely. The 2018 FAA Special Airworthiness Information Bulletin (SAIB), which highlighted disengaged locking mechanisms on Boeing 737 fuel switches (a design shared with the 787-8), was not acted upon by Air India, raising questions about mechanical reliability. However, inspections of Air India’s 787 fleet post-crash found no issues with the switches.

The Indian Commercial Pilots’ Association has condemned media speculation about pilot suicide, calling it “reckless and insensitive.” A Canada-based investigator, quoted by BBC, suggested the pilot who denied moving the switches may have done so unwittingly, perhaps in a moment of disorientation, or deliberately to deflect responsibility. The absence of cockpit video recorders, a long-standing safety debate, complicates efforts to determine who—or what—initiated the switch movement. Directional microphones on the CVR indicate the switch sounds came from the central console, not clearly from either pilot’s side, leaving open the possibility of an automated or external trigger.

Theories Under Investigation

Several scenarios are being explored:

Deliberate Interference: The SOS signal’s blockage Dedication to interference from an internal device, possibly a jammer or modified cockpit equipment, suggests sabotage. This could explain the signal’s structure and the navigation system blockage. Experts are investigating whether a crew member or unauthorized device was involved, though no evidence points to the pilots’ intent.
System Malfunction: A FADEC error, possibly triggered by electromagnetic interference, could have caused the false flameout reading and switch movement. This aligns with the 2018 SAIB but is less likely given post-crash inspections showing no mechanical issues.
Human Error: The pilots’ startled reaction and delayed response (10 seconds to reset switches) suggest possible confusion or miscommunication, exacerbated by the navigation disruption. Aviation psychologist Michael Daniel noted a “startle effect” could explain the delay.
External Jamming: Though less likely, an external signal could have infiltrated the cockpit systems, a theory echoed in the TransAsia case. This would require sophisticated equipment and access, raising security concerns.

Implications and Ongoing Probe

The AAIB, supported by international experts, is analyzing wreckage, fuel samples, and forensic data to trace the interference source. The upgraded Rs 9 crore AAIB lab in Delhi, inaugurated in April 2025, is being tested with this investigation, though challenges remain due to past reliance on foreign expertise for data decoding. No immediate safety directives have been issued for Boeing 787s or GE GEnx-1B engines, suggesting investigators lean toward human or isolated technical factors rather than systemic flaws.

The crash, the first fatal Boeing 787 incident, has spotlighted Air India’s safety record, with nine regulatory notices for violations in six months. The AI-171 Memorial and Welfare Trust, established by Tata Sons, is providing Rs 1 crore per deceased victim and rebuilding aid, but public trust in aviation safety hangs in the balance. The final report, expected within a year, must clarify whether this was a tragic outlier or a sign of deeper vulnerabilities in aviation security.

Sources:

India’s Aircraft Accident Investigation Bureau Preliminary Report, July 8, 2025
BBC News, “Air India crash report: Cockpit audio deepens mystery of Flight 171,” July 12, 2025
The Air Current, “In Air India’s wake, revisiting the case for cockpit video recorders,” July 14, 2025
Al Jazeera, “How Air India flight 171 crashed and its fatal last moments,” July 12, 2025
Airways Magazine, “Flight AI171 Initial Report Confirms Fuel Switch Movement,” July 12, 2025